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Integrative Physiology of Fasting

Stephen M. Secor, Hannah V. Carey

10.1002/cphy.c150013

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Published online: March 2016

Full Article on Wiley Online Library



ABSTRACT

Extended bouts of fasting are ingrained in the ecology of many organisms, characterizing aspects of reproduction, development, hibernation, estivation, migration, and infrequent feeding habits. The challenge of long fasting episodes is the need to maintain physiological homeostasis while relying solely on endogenous resources. To meet that challenge, animals utilize an integrated repertoire of behavioral, physiological, and biochemical responses that reduce metabolic rates, maintain tissue structure and function, and thus enhance survival. We have synthesized in this review the integrative physiological, morphological, and biochemical responses, and their stages, that characterize natural fasting bouts. Underlying the capacity to survive extended fasts are behaviors and mechanisms that reduce metabolic expenditure and shift the dependency to lipid utilization. Hormonal regulation and immune capacity are altered by fasting; hormones that trigger digestion, elevate metabolism, and support immune performance become depressed, whereas hormones that enhance the utilization of endogenous substrates are elevated. The negative energy budget that accompanies fasting leads to the loss of body mass as fat stores are depleted and tissues undergo atrophy (i.e., loss of mass). Absolute rates of body mass loss scale allometrically among vertebrates. Tissues and organs vary in the degree of atrophy and downregulation of function, depending on the degree to which they are used during the fast. Fasting affects the population dynamics and activities of the gut microbiota, an interplay that impacts the host's fasting biology. Fasting‐induced gene expression programs underlie the broad spectrum of integrated physiological mechanisms responsible for an animal's ability to survive long episodes of natural fasting. © 2016 American Physiological Society. Compr Physiol 6:773‐825, 2016.

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Figure 1. Figure 1. Animals that exemplify diverse forms of extended fasting have been valuable for exploring the ecology and physiology of fasting. For hibernation (A and B), illustrated are the 13‐lined ground squirrel (Ictidomys tridecemlineatus) and black bear (Ursus americanus); (72,74,250,264,406). For aestivation (C and D), illustrated are the African lungfish (Protopterus annectens) and green‐striped burrowing frog (Cyclorana alboguttata) in cocooned state (103,120,135,190,276,293,546); For migration (E and F), illustrated are the green sea turtle (Chelonia mydas) and the red knot (Calidris canutus) (31,253). For molting (G and H), illustrated are the king penguin (Aptenodytes patagonica) and the northern elephant seal (Mirounga angustirostris) (95,98,593). For reproduction (I and J), illustrated are the northern elephant seal and emperor penguin (Aptenodytes forsteri) (141,142,322,466). For development (K and L), illustrated are the juvenile king penguin (Aptenodytes patagonica) and grey seal (Halichoerus grypus) (97,102,148,414). For natural long bouts of fasting (M and N), illustrated are the raccoon dog (Nyctereutes procyonoides) and the Burmese python (Python molurus) (113,330,392,393,494). Photo Credit: (A) Lesa Hollen; (B) Lynn Rogers, bear.org; (C) http://en.wikipedia.org/wiki/Protopterus#mediaviewer/File:G%C5%91tehal‐2.jpg (D) E.A. Meyer; (E) Evan D'Alessandro; (F) Theunis Piersma; (G) Katie O'Reilly; (H) Dan Costa; (I) Dan Costa; (J) http://joshsjungle.com/wp‐content/uploads/2011/06/emperor‐penguin‐and‐chick.jpg; (K) http://www.factzoo.com/sites/all/img/birds/king‐penguin‐chicks.jpg; (L) Andreas Trepte; (M) http://www.factzoo.com/sites/all/img/mammals/raccoon‐dog‐nice‐coat.jpg; (N) Stephen Secor.
Figure 2. Figure 2. Circannual body temperature cycle in a 13‐lined ground squirrel (Ictidomys tridecemlineatus). The animal was housed conventionally (T a ∼ 20°C, 12:12 LD with food/water), then moved in September to a 4°C cold room in constant darkness with no food/water. Note spontaneous interbout arousals to normothermia that interrupt torpor bouts during the hibernation season. Figure courtesy of Sandy Martin, University of Colorado School of Medicine.
Figure 3. Figure 3. Energy expenditure (kJ/h) as a function of days postfeeding for the (A) common carp Cyprinus carpio, (B) Burmese python Python molurus, (C) Adelie penguin Pygoscelis adeliae, and (D) laboratory rat Rattus norvegicus. These postprandial metabolic plots illustrate the variation in metabolic rate during meal digestion and the significant decline in metabolic rate that occurs upon the completion of digestion. Figures were drawn from data presented in (86,163,291,495).
Figure 4. Figure 4. Characteristic profiles of metabolic variables during the three phases of fasting, including plasma concentrations of glucose, β‐hydroxybutyrate, urea, protein utilization, mass‐specific body mass loss, metabolic rate, and tissue concentrations of glycogen. Placement of individual profiles with respect to the Y‐axis is only illustrative and not quantitative. Figure adapted, with permission, from Figure 1 in (8).
Figure 5. Figure 5. Variation in glycogen depletion with fasting is illustrated with the relative change in liver glycogen as a function of days postfeeding for the mudskipper Boleophthalmus boddaerti, sturgeon Acipenser naccarii, bats Artibeus lituratus and A. jamaicensis (combined data), and vole Clethrionomys rufocanus. Figure drawn, with permission, from data provided in (196,331,385,438).
Figure 6. Figure 6. Plasma concentrations of glucose as a function of days of fasting for (A) subantarctic fur seal pups (Arctocephalus tropicalis) which experiences no significant change in blood glucose, (B) the Atlantic salmon (Salmo salar) which experiences an initial drop in blood glucose, (C) northern elephant seal pups (Mirounga angustirostris) which experiences a steady decline in blood glucose with fasting, and (D) greater snow geese (Chen caerulescens atlantica) whose blood glucose is maintained elevated until the entrance into phase III before declining. Figure drawn, with permission, from data presented in (45,112,520,571).
Figure 7. Figure 7. Plasma concentration of fatty acids as a function of days of fasting for (A) subantarctic fur seal pups (Arctocephalus tropicalis) and (B) molting king penguins (Aptenodytes patagonica). Fur seal pups experience a doubling of fatty acid levels with the onset of Phase II (day 4) and both animals experienced a rise in fatty acids toward the end of Phase II (day 32). Figures drawn, with permission, from data presented in (98,571).
Figure 8. Figure 8. Relative differences (in percent compared to fed active animals) in the concentration of individual fatty acids for (A) the scapular adipose tissue of the raccoon dog (Nyctereutes procyonoides) following an 8‐week fast, (B) the plasma of diamondback rattlesnakes (Crotalus atrox) fasted for 180 days, and (C) the plasma of female nonlactating black bear (Ursus americanus) following several months of hibernation. Illustrated is the dynamic nature of circulating fatty acids in response to fasting and the variation of that response among animals. Figure drawn, with permission, from data presented in (325,362,392).
Figure 9. Figure 9. Plasma concentrations of β‐hydroxybutyrate (β‐OHB) as a function of days of fasting for (A) subantarctic fur seal pups (Arctocephalus tropicalis), (B) greater snow geese (Chen caerulescens atlantica), and (C) breeding male king penguins (Aptenodytes patagonica). For these species, β‐OHB steadily increased with fasting however peaked midway through Phase II fasting for the snow geese and king penguins before declining and returning to initial levels during Phase III. Figures were drawn, with permission, from data presented in (45,101,571).
Figure 10. Figure 10. Plasma concentrations of triglycerides and cholesterol as a function of days of fasting for the (A) trout Oncorhynchus mykiss, (B) mink Mustela vison, and (C) Burmese python Python molurus. For the Burmese python, the start of the fast is noted at 3 days postfeeding when plasma triglycerides peaked. Both the trout and python experienced an initial decrease in plasma triglycerides that was not experienced by the mink. Python possess nondetectable levels of triglycerides in their plasma once they have completed digestion. Fasting resulted in a modest decrease in plasma cholesterol for the trout, but remained unchanged for both the python and mink. Figures were drawn, with permission, from data presented in (41,196) and (S. Secor, unpublished data).
Figure 11. Figure 11. (A) Plasma concentration of proteins as a function of days of fasting for the greater snow geese (Chen caerulescens atlantica). Protein levels remain relatively stable through phase I and II, before declining with the onset of Phase III (day 30). (B) The relative change in plasma concentrations of amino acids following 8 weeks of fasting for the raccoon dog (Nyctereutes procyonoides). While the majority of amino acids decreased in concentration, two amino acids (glutamine and serine) increased. Figures drawn, with permission, from data presented in (45,392).
Figure 12. Figure 12. Plasma concentrations of urea and uric acid as a function of days of fasting for (A) breeding male king penguin (Aptenodytes patagonica) and (B) the common buzzard (Buteo buteo) For the king penguin plasma urea and uric acid concentrations slowly increased during phase II fasting and rose more steeply with transition to Phase III (∼day 35). For the buzzard, both urea and uric acid peak midway through the fast. Figures were drawn, with permission, from data presented (101,202).
Figure 13. Figure 13. Plasma urea (stippled) and total osmolality (solid) of active and fed (red) and aestivated and fasted (blue) greater siren (Siren lacertina), northern burrowing frog (Neobatrachus aquilonius), African bullfrog (Pxyicephalus adspersus), western spotted frog (Heleioporus albopunctatus), Kunapalari frog (Neobatrachus kunapalari), humming frog (Neobatrachus pelobatoides), and Couch's spadefoot toad (Scaphiopus couchii). Duration of aestivation range from 2 to 8.5 months. During aestivation, amphibians accumulate urea in their blood which contributes in some cases to a doubling of plasma osmolality. Figure drawn, with permission, from data presented in (160,339,358,589).
Figure 14. Figure 14. Plasma concentrations of glucagon, insulin, corticosterone or cortisol, triiodothyronine (T 3), and thyroxin (T 4) as a function of days fasting for breeding male king penguins (Aptenodytes patagonicus) and raccoon dogs (Nyctereutes procyonoides). With the exception of glucagon, which increased with time fasting for both species, plasma concentrations of the other five hormones experienced contrasting fasting profiles. Figures drawn, with permission, from data presented in (101,393).
Figure 15. Figure 15. Plasma concentration of (A) immunoglobulin (IgY), (B) natural antibodies (NABs), and (C) corticosterone for fasted and refed female mallard ducks (Anas platyhyrhychos). Sampling treatments included fed, 48‐h fasted, phase II of fasting (PII), phase III of fasting (PIII), fasted to PIII and refed for 1 day (RI), fasted to PIII and refed for 3 days (R3), and fasted to PIII and refed to recovery of initial body mass (Rt). Note the fasting decline in immune function and rapid increase in corticosterone, both reversed with refeeding. Figures drawn, with permission, from data presented in (48).
Figure 16. Figure 16. Relative change in body mass and individual organs and tissues as a function of time fasting for (A) the fish Clarius lazera, (B) the snake Nerodia rhombifer, and (C) the rat Rattus norvegicus. Compared to the rate of body mass loss, individual organs and tissue lose mass at a lower or greater rate with time fasting. Figures for Clarius lazera and Rattus norvegicus were drawn, with permission, respectively, from data presented in (243) and (219). Figure for Nerodia rhombifer was drawn, with permission, from unpublished data of M. Larkin and S. Secor.
Figure 17. Figure 17. Absolute (g day−1) and mass specific (g kg−1 day−1) loss of body mass plotted against body mass for birds, mammals, and ectotherms. Data were generated from studies that provided body mass before and after a known period of fasting. Note the near identical allometric scaling exponents for birds, mammals, and ectotherms.
Figure 18. Figure 18. Mass specific daily loss of body mass illustrated for the three phases of fasting for (A) common barn owl (Tyto alba) and (B) breeding king penguin (Aptenodytes patagonica). Birds experienced greater specific mass loss during phases I and III of fasting compared to phase II. Figures drawn, with permission, from data presented in (101,242).
Figure 19. Figure 19. (A) Micrographs of intraperitoneal fat bodies from king penguin chicks (Aptenodytes patagonicus) following control feeding (NCA), three weeks of laboratory fasting (STF), and several months of a natural fast (LTF) (148). Mass of regional fat deposits of fed (closed bars) and fasted (open bars) (B) raccoon dog (Nyctereutes procyonoides) and (C) American marten (Martes americana). Raccoon dogs and martens had been fasted for 56 and 2 days, respectively. Illustrated is the characteristic depletion of fat stores during fasting. Figures B and C were drawn, with permission, from data presented in (392,410).
Figure 20. Figure 20. Electron micrographs of (A) gastrocnemius and (B) pectoralis muscle sampled from king penguin chicks (Aptenodytes patagonicus) following control feeding (NCA), 3 weeks of laboratory fasting (STF), and several months of a natural fast (LTF) as presented in (148). Below each set of micrographs is the relative mass (% of body mass) of these muscles for each treatment. Note the loss of sarcomere integrity following the natural fast (LTF) for both muscles, and the increase in relative mass of the gastrocnemius but decrease in relative mass of the pectoralis with duration of the fast. Figures illustrating relative muscle masses are drawn, with permission, from data presented in (148).
Figure 21. Figure 21. (A) mean cross‐sectional area (blue) and density (red) of fast‐ and slow‐twitch muscle fibers in the gastrocnemius and biceps femoris of black bears (Ursus americanus) prior to hibernation (fall, open bars) and immediately following hibernation (spring, closed bars). (B) Citrate synthase (CS) activity (blue) of gastrocnemius and biceps femoris muscles and contraction force (red) of the tibialis anterior muscle determined from bears sampled in the fall or early in hibernation (open bars) and sampled in the spring or late in hibernation (closed bars). (C) Twitch parameters of the tibialis anterior muscle for black bears measured early and late during hibernation. Illustrated is the lack of change in muscle structure and function for black bears during hibernation. Figures drawn, with permission, from data presented in (333,554).
Figure 22. Figure 22. (A) Muscle dry mass, (B) muscle fiber density, (C) maximum stress twitch, and (D) peak power output for the gastrocnemius, iliofibularis, and sartorius muscles for control (fed and active) Cyclorana alboguttata and following 9 months of aestivation. This frog did not experience any loss in muscle mass or performance even after 9 months of aestivation. Figures drawn, with permission, from data presented in (350,546).
Figure 23. Figure 23. Gastric pH profile for the (A) dog (Canis familiaris), (B) leopard shark (Triakis semifasciata), (C) white sea bream (Sparus aurata), and (D) Burmese python (Python molurus). The downturn arrows note the time of feeding and the upturn arrows note the time of gastric emptying. For the dog and leopard shark, the stomach remains acidic and experiences an increase in pH with feeding (due to the buffering effects of the food). In contrast, the white sea bream and python maintain a near neutral gastric pH while fasting, experience a rapid drop in pH during digestion, and then curtail acid production with the emptying of the stomach. Figures are drawn, with permission, from data presented in (426,489,603,604).
Figure 24. Figure 24. Fasting‐induced changes (relative to fed state) in (A) small intestinal mass, (B) mucosal thickness, and (C) enterocyte volume for Micropterus salmoides, Cyclorana alboguttata, Pyxicephalus adspersus, Chelydra serpentina, Heloderma suspectum, Python molurus, Nerodia rhombifer, Passer domesticus, and Ictidomys tridecemlineatus. Noted is the condition and duration of the fast for each species. All species experience a fasting reduction in small intestinal mass, mucosal thickness, and enterocyte volume, however there is considerable variation in the extent of the reduction. Figures drawn, with permission, from data presented in (71,92,104,119,131,330,499) and (S. Secor and D. Crossley, unpublished data).
Figure 25. Figure 25. Electron micrographs of intestinal microvilli of fed and fasted 13‐lined ground squirrel Ictidomys tridecemlineatus diamondback water snake Nerodia rhombifer, channel catfish Ictalurus punctatus, vermiculated sailfin catfish Pterygoplichthys disjunctivus, Gila monster Heloderma suspectum, South American horn frog Ceratophrys ornata, African bullfrog Pyxicephalus adspersus, and Burmese python Python molurus (77,104,119,131,214,330,499). Fasting conditions are respectively; 6‐week hibernation, 30‐day fast, 5‐day fast, 150‐day fast, 30‐day fast, 1‐month aestivation, 1‐month aestivation, and 30‐day fast. Below each set of micrographs is illustrated the relative change in microvillus length with fasting.
Figure 26. Figure 26. Fasting generated changes (relative to fed state) in small intestinal (A) aminopeptidase activity, (B) maltase or sucrase activity, (C) D‐glucose uptake, and (D) L‐proline uptake for Ctenopharyngodon idella, Ceratophrys ornata, Amphiuma tridactylum, Chelydra serpentina, Heloderma suspectum, Python molurus, Nerodia rhombifer, Passer domesticus, and Ictidomys tridecemlineatus. Noted is the condition and duration of the fast for each species. Among these species, there is considerable variation in magnitude by which intestinal function is regulated with fasting, ranging from sever downregulation, to no change, to significant increases in mass‐specific function. Figures drawn, with permission, from data presented in (71,92,104,118,119,131,494,499) and (S. Secor and D. Crossley, unpublished data; S. Secor and M. Smith, unpublished data).
Figure 27. Figure 27. Correspondence between temporal changes in microvillus surface area (MVSA, black) and intestinal function (blue) with fasting for (A) the Burmese python (Python molurus) and (B) the southern catfish (Silurus meridionalis). In this figure, MVSA is compared with L‐proline uptake rates for P. molurus and with aminopeptidase activity for S. meridionalis. Electron micrographs of intestinal microvilli at each time point demonstrate the fasting‐related shortening of the microvilli and hence decrease in MVSA. Micrographs and the data used to make figures originate, with permission, from (119,330,606).
Figure 28. Figure 28. Fasting related change in wet mass of the (A) heart, (b) liver, (C) gall bladder, (D) pancreas, and (E) kidneys for the Burmese python (Python molurus). Time zero (0) represents the time point postfeeding (2 or 3 days) that each organ was at its maximum (heart, liver, pancreas, and kidneys) or minimum (gall bladder) mass. The insert for (D) illustrates the decline with fasting of pancreas' capacity for amylase activity. Figures drawn, with permission, from data presented in (119) and (S. Secor, unpublished data).
Figure 29. Figure 29. (A) Postprandial separation of the relative percentages of the microbiota phylums Bacteroidetes and Firmicutes within the large intestine for the Burmese python (Python molurus). Within hours of feeding, Firmicutes come to dominate the microbiota community, while the contribution of Bacteroidetes is greatly depressed. With the clearing of the intestine and through fasting, both phyla then contribute equally to the microbiota community. (B). The relative abundance of microbiota phyla in cecal contents of 13‐line ground squirrels (Ictidomys tridecemlineatus) during summer activity, early and late winter hibernation, and spring activity 2 weeks postfeeding. Note the shifts with hibernation of the phyla Bacteroidetes, Firmicutes, and Verrucomicrobia. Figures drawn, with permission, from data presented in (78,113).
Figure 30. Figure 30. (A) Representation of the up‐ and downregulation of cellular function by the differential expression of genes within the gastrocnemius muscle of green‐striped burrowing frogs (Cyclorana alboguttata) following 4 months of aestivation. Plots represent the −log of the P value stemming from Ingenuity Pathway Analysis. (B) Up and downregulation of genes following a 1 month fast (compared to 1‐day fed) for the heart, kidneys, liver, and small intestine of the Burmese python (Python molurus). Genes include those involved in transcription (DDX21), translation (Rmb4), development (GPR180), and metabolism (PDK4). Plots illustrate log2 fold change in expression. (C) Factorial changes in mRNA abundance of genes of the heart, muscle, and white adipose between summer (August) active and hibernating torpor 13‐lined ground squirrels (Ictidomys tridecemlineatus). Figures drawn, with permission, from data presented in (84,240,448).


Figure 1. Animals that exemplify diverse forms of extended fasting have been valuable for exploring the ecology and physiology of fasting. For hibernation (A and B), illustrated are the 13‐lined ground squirrel (Ictidomys tridecemlineatus) and black bear (Ursus americanus); (72,74,250,264,406). For aestivation (C and D), illustrated are the African lungfish (Protopterus annectens) and green‐striped burrowing frog (Cyclorana alboguttata) in cocooned state (103,120,135,190,276,293,546); For migration (E and F), illustrated are the green sea turtle (Chelonia mydas) and the red knot (Calidris canutus) (31,253). For molting (G and H), illustrated are the king penguin (Aptenodytes patagonica) and the northern elephant seal (Mirounga angustirostris) (95,98,593). For reproduction (I and J), illustrated are the northern elephant seal and emperor penguin (Aptenodytes forsteri) (141,142,322,466). For development (K and L), illustrated are the juvenile king penguin (Aptenodytes patagonica) and grey seal (Halichoerus grypus) (97,102,148,414). For natural long bouts of fasting (M and N), illustrated are the raccoon dog (Nyctereutes procyonoides) and the Burmese python (Python molurus) (113,330,392,393,494). Photo Credit: (A) Lesa Hollen; (B) Lynn Rogers, bear.org; (C) http://en.wikipedia.org/wiki/Protopterus#mediaviewer/File:G%C5%91tehal‐2.jpg (D) E.A. Meyer; (E) Evan D'Alessandro; (F) Theunis Piersma; (G) Katie O'Reilly; (H) Dan Costa; (I) Dan Costa; (J) http://joshsjungle.com/wp‐content/uploads/2011/06/emperor‐penguin‐and‐chick.jpg; (K) http://www.factzoo.com/sites/all/img/birds/king‐penguin‐chicks.jpg; (L) Andreas Trepte; (M) http://www.factzoo.com/sites/all/img/mammals/raccoon‐dog‐nice‐coat.jpg; (N) Stephen Secor.


Figure 2. Circannual body temperature cycle in a 13‐lined ground squirrel (Ictidomys tridecemlineatus). The animal was housed conventionally (T a ∼ 20°C, 12:12 LD with food/water), then moved in September to a 4°C cold room in constant darkness with no food/water. Note spontaneous interbout arousals to normothermia that interrupt torpor bouts during the hibernation season. Figure courtesy of Sandy Martin, University of Colorado School of Medicine.


Figure 3. Energy expenditure (kJ/h) as a function of days postfeeding for the (A) common carp Cyprinus carpio, (B) Burmese python Python molurus, (C) Adelie penguin Pygoscelis adeliae, and (D) laboratory rat Rattus norvegicus. These postprandial metabolic plots illustrate the variation in metabolic rate during meal digestion and the significant decline in metabolic rate that occurs upon the completion of digestion. Figures were drawn from data presented in (86,163,291,495).


Figure 4. Characteristic profiles of metabolic variables during the three phases of fasting, including plasma concentrations of glucose, β‐hydroxybutyrate, urea, protein utilization, mass‐specific body mass loss, metabolic rate, and tissue concentrations of glycogen. Placement of individual profiles with respect to the Y‐axis is only illustrative and not quantitative. Figure adapted, with permission, from Figure 1 in (8).


Figure 5. Variation in glycogen depletion with fasting is illustrated with the relative change in liver glycogen as a function of days postfeeding for the mudskipper Boleophthalmus boddaerti, sturgeon Acipenser naccarii, bats Artibeus lituratus and A. jamaicensis (combined data), and vole Clethrionomys rufocanus. Figure drawn, with permission, from data provided in (196,331,385,438).


Figure 6. Plasma concentrations of glucose as a function of days of fasting for (A) subantarctic fur seal pups (Arctocephalus tropicalis) which experiences no significant change in blood glucose, (B) the Atlantic salmon (Salmo salar) which experiences an initial drop in blood glucose, (C) northern elephant seal pups (Mirounga angustirostris) which experiences a steady decline in blood glucose with fasting, and (D) greater snow geese (Chen caerulescens atlantica) whose blood glucose is maintained elevated until the entrance into phase III before declining. Figure drawn, with permission, from data presented in (45,112,520,571).


Figure 7. Plasma concentration of fatty acids as a function of days of fasting for (A) subantarctic fur seal pups (Arctocephalus tropicalis) and (B) molting king penguins (Aptenodytes patagonica). Fur seal pups experience a doubling of fatty acid levels with the onset of Phase II (day 4) and both animals experienced a rise in fatty acids toward the end of Phase II (day 32). Figures drawn, with permission, from data presented in (98,571).


Figure 8. Relative differences (in percent compared to fed active animals) in the concentration of individual fatty acids for (A) the scapular adipose tissue of the raccoon dog (Nyctereutes procyonoides) following an 8‐week fast, (B) the plasma of diamondback rattlesnakes (Crotalus atrox) fasted for 180 days, and (C) the plasma of female nonlactating black bear (Ursus americanus) following several months of hibernation. Illustrated is the dynamic nature of circulating fatty acids in response to fasting and the variation of that response among animals. Figure drawn, with permission, from data presented in (325,362,392).


Figure 9. Plasma concentrations of β‐hydroxybutyrate (β‐OHB) as a function of days of fasting for (A) subantarctic fur seal pups (Arctocephalus tropicalis), (B) greater snow geese (Chen caerulescens atlantica), and (C) breeding male king penguins (Aptenodytes patagonica). For these species, β‐OHB steadily increased with fasting however peaked midway through Phase II fasting for the snow geese and king penguins before declining and returning to initial levels during Phase III. Figures were drawn, with permission, from data presented in (45,101,571).


Figure 10. Plasma concentrations of triglycerides and cholesterol as a function of days of fasting for the (A) trout Oncorhynchus mykiss, (B) mink Mustela vison, and (C) Burmese python Python molurus. For the Burmese python, the start of the fast is noted at 3 days postfeeding when plasma triglycerides peaked. Both the trout and python experienced an initial decrease in plasma triglycerides that was not experienced by the mink. Python possess nondetectable levels of triglycerides in their plasma once they have completed digestion. Fasting resulted in a modest decrease in plasma cholesterol for the trout, but remained unchanged for both the python and mink. Figures were drawn, with permission, from data presented in (41,196) and (S. Secor, unpublished data).


Figure 11. (A) Plasma concentration of proteins as a function of days of fasting for the greater snow geese (Chen caerulescens atlantica). Protein levels remain relatively stable through phase I and II, before declining with the onset of Phase III (day 30). (B) The relative change in plasma concentrations of amino acids following 8 weeks of fasting for the raccoon dog (Nyctereutes procyonoides). While the majority of amino acids decreased in concentration, two amino acids (glutamine and serine) increased. Figures drawn, with permission, from data presented in (45,392).


Figure 12. Plasma concentrations of urea and uric acid as a function of days of fasting for (A) breeding male king penguin (Aptenodytes patagonica) and (B) the common buzzard (Buteo buteo) For the king penguin plasma urea and uric acid concentrations slowly increased during phase II fasting and rose more steeply with transition to Phase III (∼day 35). For the buzzard, both urea and uric acid peak midway through the fast. Figures were drawn, with permission, from data presented (101,202).


Figure 13. Plasma urea (stippled) and total osmolality (solid) of active and fed (red) and aestivated and fasted (blue) greater siren (Siren lacertina), northern burrowing frog (Neobatrachus aquilonius), African bullfrog (Pxyicephalus adspersus), western spotted frog (Heleioporus albopunctatus), Kunapalari frog (Neobatrachus kunapalari), humming frog (Neobatrachus pelobatoides), and Couch's spadefoot toad (Scaphiopus couchii). Duration of aestivation range from 2 to 8.5 months. During aestivation, amphibians accumulate urea in their blood which contributes in some cases to a doubling of plasma osmolality. Figure drawn, with permission, from data presented in (160,339,358,589).


Figure 14. Plasma concentrations of glucagon, insulin, corticosterone or cortisol, triiodothyronine (T 3), and thyroxin (T 4) as a function of days fasting for breeding male king penguins (Aptenodytes patagonicus) and raccoon dogs (Nyctereutes procyonoides). With the exception of glucagon, which increased with time fasting for both species, plasma concentrations of the other five hormones experienced contrasting fasting profiles. Figures drawn, with permission, from data presented in (101,393).


Figure 15. Plasma concentration of (A) immunoglobulin (IgY), (B) natural antibodies (NABs), and (C) corticosterone for fasted and refed female mallard ducks (Anas platyhyrhychos). Sampling treatments included fed, 48‐h fasted, phase II of fasting (PII), phase III of fasting (PIII), fasted to PIII and refed for 1 day (RI), fasted to PIII and refed for 3 days (R3), and fasted to PIII and refed to recovery of initial body mass (Rt). Note the fasting decline in immune function and rapid increase in corticosterone, both reversed with refeeding. Figures drawn, with permission, from data presented in (48).


Figure 16. Relative change in body mass and individual organs and tissues as a function of time fasting for (A) the fish Clarius lazera, (B) the snake Nerodia rhombifer, and (C) the rat Rattus norvegicus. Compared to the rate of body mass loss, individual organs and tissue lose mass at a lower or greater rate with time fasting. Figures for Clarius lazera and Rattus norvegicus were drawn, with permission, respectively, from data presented in (243) and (219). Figure for Nerodia rhombifer was drawn, with permission, from unpublished data of M. Larkin and S. Secor.


Figure 17. Absolute (g day−1) and mass specific (g kg−1 day−1) loss of body mass plotted against body mass for birds, mammals, and ectotherms. Data were generated from studies that provided body mass before and after a known period of fasting. Note the near identical allometric scaling exponents for birds, mammals, and ectotherms.


Figure 18. Mass specific daily loss of body mass illustrated for the three phases of fasting for (A) common barn owl (Tyto alba) and (B) breeding king penguin (Aptenodytes patagonica). Birds experienced greater specific mass loss during phases I and III of fasting compared to phase II. Figures drawn, with permission, from data presented in (101,242).


Figure 19. (A) Micrographs of intraperitoneal fat bodies from king penguin chicks (Aptenodytes patagonicus) following control feeding (NCA), three weeks of laboratory fasting (STF), and several months of a natural fast (LTF) (148). Mass of regional fat deposits of fed (closed bars) and fasted (open bars) (B) raccoon dog (Nyctereutes procyonoides) and (C) American marten (Martes americana). Raccoon dogs and martens had been fasted for 56 and 2 days, respectively. Illustrated is the characteristic depletion of fat stores during fasting. Figures B and C were drawn, with permission, from data presented in (392,410).


Figure 20. Electron micrographs of (A) gastrocnemius and (B) pectoralis muscle sampled from king penguin chicks (Aptenodytes patagonicus) following control feeding (NCA), 3 weeks of laboratory fasting (STF), and several months of a natural fast (LTF) as presented in (148). Below each set of micrographs is the relative mass (% of body mass) of these muscles for each treatment. Note the loss of sarcomere integrity following the natural fast (LTF) for both muscles, and the increase in relative mass of the gastrocnemius but decrease in relative mass of the pectoralis with duration of the fast. Figures illustrating relative muscle masses are drawn, with permission, from data presented in (148).


Figure 21. (A) mean cross‐sectional area (blue) and density (red) of fast‐ and slow‐twitch muscle fibers in the gastrocnemius and biceps femoris of black bears (Ursus americanus) prior to hibernation (fall, open bars) and immediately following hibernation (spring, closed bars). (B) Citrate synthase (CS) activity (blue) of gastrocnemius and biceps femoris muscles and contraction force (red) of the tibialis anterior muscle determined from bears sampled in the fall or early in hibernation (open bars) and sampled in the spring or late in hibernation (closed bars). (C) Twitch parameters of the tibialis anterior muscle for black bears measured early and late during hibernation. Illustrated is the lack of change in muscle structure and function for black bears during hibernation. Figures drawn, with permission, from data presented in (333,554).


Figure 22. (A) Muscle dry mass, (B) muscle fiber density, (C) maximum stress twitch, and (D) peak power output for the gastrocnemius, iliofibularis, and sartorius muscles for control (fed and active) Cyclorana alboguttata and following 9 months of aestivation. This frog did not experience any loss in muscle mass or performance even after 9 months of aestivation. Figures drawn, with permission, from data presented in (350,546).


Figure 23. Gastric pH profile for the (A) dog (Canis familiaris), (B) leopard shark (Triakis semifasciata), (C) white sea bream (Sparus aurata), and (D) Burmese python (Python molurus). The downturn arrows note the time of feeding and the upturn arrows note the time of gastric emptying. For the dog and leopard shark, the stomach remains acidic and experiences an increase in pH with feeding (due to the buffering effects of the food). In contrast, the white sea bream and python maintain a near neutral gastric pH while fasting, experience a rapid drop in pH during digestion, and then curtail acid production with the emptying of the stomach. Figures are drawn, with permission, from data presented in (426,489,603,604).


Figure 24. Fasting‐induced changes (relative to fed state) in (A) small intestinal mass, (B) mucosal thickness, and (C) enterocyte volume for Micropterus salmoides, Cyclorana alboguttata, Pyxicephalus adspersus, Chelydra serpentina, Heloderma suspectum, Python molurus, Nerodia rhombifer, Passer domesticus, and Ictidomys tridecemlineatus. Noted is the condition and duration of the fast for each species. All species experience a fasting reduction in small intestinal mass, mucosal thickness, and enterocyte volume, however there is considerable variation in the extent of the reduction. Figures drawn, with permission, from data presented in (71,92,104,119,131,330,499) and (S. Secor and D. Crossley, unpublished data).


Figure 25. Electron micrographs of intestinal microvilli of fed and fasted 13‐lined ground squirrel Ictidomys tridecemlineatus diamondback water snake Nerodia rhombifer, channel catfish Ictalurus punctatus, vermiculated sailfin catfish Pterygoplichthys disjunctivus, Gila monster Heloderma suspectum, South American horn frog Ceratophrys ornata, African bullfrog Pyxicephalus adspersus, and Burmese python Python molurus (77,104,119,131,214,330,499). Fasting conditions are respectively; 6‐week hibernation, 30‐day fast, 5‐day fast, 150‐day fast, 30‐day fast, 1‐month aestivation, 1‐month aestivation, and 30‐day fast. Below each set of micrographs is illustrated the relative change in microvillus length with fasting.


Figure 26. Fasting generated changes (relative to fed state) in small intestinal (A) aminopeptidase activity, (B) maltase or sucrase activity, (C) D‐glucose uptake, and (D) L‐proline uptake for Ctenopharyngodon idella, Ceratophrys ornata, Amphiuma tridactylum, Chelydra serpentina, Heloderma suspectum, Python molurus, Nerodia rhombifer, Passer domesticus, and Ictidomys tridecemlineatus. Noted is the condition and duration of the fast for each species. Among these species, there is considerable variation in magnitude by which intestinal function is regulated with fasting, ranging from sever downregulation, to no change, to significant increases in mass‐specific function. Figures drawn, with permission, from data presented in (71,92,104,118,119,131,494,499) and (S. Secor and D. Crossley, unpublished data; S. Secor and M. Smith, unpublished data).


Figure 27. Correspondence between temporal changes in microvillus surface area (MVSA, black) and intestinal function (blue) with fasting for (A) the Burmese python (Python molurus) and (B) the southern catfish (Silurus meridionalis). In this figure, MVSA is compared with L‐proline uptake rates for P. molurus and with aminopeptidase activity for S. meridionalis. Electron micrographs of intestinal microvilli at each time point demonstrate the fasting‐related shortening of the microvilli and hence decrease in MVSA. Micrographs and the data used to make figures originate, with permission, from (119,330,606).


Figure 28. Fasting related change in wet mass of the (A) heart, (b) liver, (C) gall bladder, (D) pancreas, and (E) kidneys for the Burmese python (Python molurus). Time zero (0) represents the time point postfeeding (2 or 3 days) that each organ was at its maximum (heart, liver, pancreas, and kidneys) or minimum (gall bladder) mass. The insert for (D) illustrates the decline with fasting of pancreas' capacity for amylase activity. Figures drawn, with permission, from data presented in (119) and (S. Secor, unpublished data).


Figure 29. (A) Postprandial separation of the relative percentages of the microbiota phylums Bacteroidetes and Firmicutes within the large intestine for the Burmese python (Python molurus). Within hours of feeding, Firmicutes come to dominate the microbiota community, while the contribution of Bacteroidetes is greatly depressed. With the clearing of the intestine and through fasting, both phyla then contribute equally to the microbiota community. (B). The relative abundance of microbiota phyla in cecal contents of 13‐line ground squirrels (Ictidomys tridecemlineatus) during summer activity, early and late winter hibernation, and spring activity 2 weeks postfeeding. Note the shifts with hibernation of the phyla Bacteroidetes, Firmicutes, and Verrucomicrobia. Figures drawn, with permission, from data presented in (78,113).


Figure 30. (A) Representation of the up‐ and downregulation of cellular function by the differential expression of genes within the gastrocnemius muscle of green‐striped burrowing frogs (Cyclorana alboguttata) following 4 months of aestivation. Plots represent the −log of the P value stemming from Ingenuity Pathway Analysis. (B) Up and downregulation of genes following a 1 month fast (compared to 1‐day fed) for the heart, kidneys, liver, and small intestine of the Burmese python (Python molurus). Genes include those involved in transcription (DDX21), translation (Rmb4), development (GPR180), and metabolism (PDK4). Plots illustrate log2 fold change in expression. (C) Factorial changes in mRNA abundance of genes of the heart, muscle, and white adipose between summer (August) active and hibernating torpor 13‐lined ground squirrels (Ictidomys tridecemlineatus). Figures drawn, with permission, from data presented in (84,240,448).
References
 1. Abe AS . Estivation in South American amphibians and reptiles. Braz J Med Biol Res 28: 1241‐1247, 1995.
 2. Abnous K , Dieni CA , Storey KB . Regulation of Akt during hibernation in Richardson's ground squirrels. Biochim Biophys Acta 1780: 185‐193, 2008.
 3. Abolfathi M , Hajimoradloo A , Ghorbani R , Zamani A . Effect of starvation and refeeding on digestive enzyme activities in juvenile roach, Rutilus rutilus caspicus. Comp Biochem Physiol A 161: 166‐173, 2012.
 4. Aleksiuk M . Temperature‐dependent shifts in the metabolism of a cool temperate reptile, Thamnophis sirtalis parietalis . Comp Biochem Physiol A 39: 495‐503, 1971.
 5. Alerstam T , Hendenström A , Åkesson S . Long‐distance migration: Evolution and determinants. Oikos 103: 247‐260, 2003.
 6. Allan ME , Storey KB . Expression of NF‐κB and downstream antioxidant genes in skeletal muscle of hibernating ground squirrels, Spermophilus tridecemlineatus . Cell Biochem Funct 30: 166‐174, 2012.
 7. Allen WV . Biochemical aspects of lipid storage and utilization in animals. Am Zool 16: 631‐647, 1976.
 8. Alonso‐Alvarez C , Ferrer M . A biochemical study of fasting, subfeeding, and recovery processes in yellow‐legged gulls. Physiol Biochem Zool 74: 703‐713, 2001.
 9. Altmann GG . Influence of starvation and refeeding on mucosal size and epithelial renewal in the rat small intestine. Am J Anat 133: 391‐400, 1972.
 10. Ancel A , Fetter L , Groscolas R . Changes in egg and body temperature indicate triggering of egg desertion at a body mass threshold in fasting incubating blue petrels (Halobaena caerulea). J Comp Physiol B 168: 533‐539, 1998.
 11. Andersen JB , Rourke BC , Caiozzo VJ , Bennett AF , Hicks JW . Physiology: Postprandial cardiac hypertrophy in pythons. Nature 434: 37‐38, 2005.
 12. Andres‐Mateos E , Brinkmeier H , Burks TN , Mejias R , Files DC , Steinberger M , Soleimani A , Marx R , Simmers JL , Lin B , Finanger Hedderick E , Marr TG , Lin BM , Hourde C , Leinwand LA , Kuhl D , Foller M , Vogelsang S , Hernandez‐Diaz I , Vaughan DK , Alvarez de la Rosa D , Lang F , Cohn RD . Activation of serum/glucocorticoid‐induced kinase 1 (SGK1) is important to maintain skeletal muscle homeostasis and prevent atrophy. EMBO Mol Med 5: 80‐91, 2013.
 13. Andrew AL , Card DC , Ruggiero RP , Schield DR , Adams RH , Pollock DD , Secor SM , Castoe TA . Rapid changes in gene expression direct rapid shifts in intestinal form and function in the Burmese python after feeding. Physiol Genomics 47: 147‐157, 2015.
 14. Andrews MT , Squire TL , Bowen CM , Rollins MB . Low‐temperature carbon utilization is regulated by novel gene activity in the heart of a hibernating mammal. Proc Natl Acad Sci U S A 95: 8392‐8397, 1998.
 15. Ankney CD . Feeding and digestive organ size in breeding lesser snow geese. Auk 94: 275‐282, 1977.
 16. Ankney CD , MacInnes CD . Nutrient reserves and reproductive‐performance of femalel lesser snow geese. Auk 95: 459‐471, 1978.
 17. Araki S , Goto S . Age‐associated changes in the serum level of apolipoproteins A‐I and A‐IV and the gene expression as revealed by fasting and refeeding in mice. Exp Gerontol 38: 499‐506, 2003.
 18. Armitage KB , Woods BC . Group hibernation does not reduce energetic costs of young yellow‐bellied marmots. Physiol Biochem Zool 76: 888‐898, 2003.
 19. Arnould JP , Green JA , Rawlins DR . Fasting metabolism in Antarctic fur seal (Arctocephalus gazella) pups. Comp Biochem Physiol A 129: 829‐841, 2001.
 20. Atkinson SN , Nelson RA , Ramsay MA . Changes in the body composition of fasting polar bears (Ursus maritimus): The effect of relative fatness on protein conservation. Physiol Zool 69: 304‐316, 1996.
 21. Aubret F , Bonnet X , Shine R , Maumelat S . Clutch size manipulation, hatching success and offspring phenotype in the ball python (Python regius). Biol J Linn Soc 78: 263‐272, 2003.
 22. Aw TY . Molecular and cellular responses to oxidative stress and changes in oxidation‐reduction imbalance in the intestine. Am J Clin Nutr 70: 557‐565, 1999.
 23. Azizi F , Mannix JE , Howard D , Nelson RA . Effect of winter sleep on pituitary‐thyroid axis in American black bear. Am J Physiol Endocrinol Metab 237: E227‐E230, 1979.
 24. Balinsky JB , Choritz EL , Coe CGL , Van der Schans GS . Amino acid metabolism and urea synthesis in naturally aestivating Xenopus laevis . Comp Biochem Physiol 22: 59‐68, 1967.
 25. Balslev‐Clausen A , McCarthy JM , Carey HV . Hibernation reduces pancreatic amylase levels in ground squirrels. Comp Biochem Physiol A 134: 573‐578, 2003.
 26. Bar B . Physiological and hormonal changes during prolonged starvation in fish. Can J Fish Aquat Sci 71: 1‐12, 2013.
 27. Barboza PS , Farley SD , Robbins CT . Whole‐body urea cycling and protein turnover during hyperphagia and dormancy in growing bears (Ursus americanus and U. arctos). Can J Zool 75: 2129‐2136, 1997.
 28. Barger JL , Barnes BM , Boyer BB . Regulation of UCP1 and UCP3 in arctic ground squirrels and relation with mitochondrial proton leak. J Appl Physiol 101: 339‐347, 2006.
 29. Barter M , Hou WT . Can waders fly non‐stop from Australia to China? Stilt 17: 36‐39, 1990.
 30. Bashan A , Bartsch RP , Kantelhardt JW , Havlin S , Ivanov P . Network physiology reveals relations between network topology and physiological function. Nat Commun 3: 702, 2012.
 31. Battley PF , Dietz MW , Piersma T , Dekinga A , Tang S , Hulsman K . Is long distance bird flight equivalent to a high‐energy fast? Body composition changes in freely migrating and captive fasting great knots. Physiol Biochem Zool 74: 435‐449, 2001.
 32. Bauman WA . Seasonal changes in pancreatic insulin and glucagon in the little brown bat (Myotis lucifugus). Pancreas 5: 342‐346, 1990.
 33. Bauman WA , Meryn S , Florant GL . Pancreatic hormones in the nonhibernating and hibernating golden mantled ground squirrel. Comp Biochem Physiol A 86: 241‐244, 1987.
 34. Baumber J , South FE , Ferren L , Zatzman ML . A possible basis for periodic arousals during hibernation: Accumulation of ketone bodies. Life Sci II 10: 463‐467, 1971.
 35. Ben‐Hamo M , McCue MD , Khozin‐Goldberg I , McWilliams SR , Pinshow B . Ambient temperature and nutritional stress influence fatty acid composition of structural and fuel lipids in Japanese quail (Coturnix japonica) tissues. Comp Biochem Physiol A 166: 244‐250, 2013.
 36. Bentley GE , Bonser RH . Long‐term hypothyroidism causes decreased bone competence in male European starlings, Sturnus vulgaris . J Exp Zool 281: 602‐607, 1998.
 37. Bergman EN . Energy contributions of volatile fatty acids from the gastrointestinal tract in various species. Physiol Rev 70: 567‐590, 1990.
 38. Bernard SF , Fayolle C , Robin J‐P , Groscolas R . Glycerol and NEFA kinetics in long‐term fasting king penguins: Phase II versus phase III. J Exp Biol 205: 2745‐2754, 2002.
 39. Bernard SF , Thil M‐A , Groscolas R . Lipolytic and metabolic response to glucagon in fasting king penguins: Phase II vs. phase III. Am J Physiol Regul Integr Comp Physiol 284: R444‐R454, 2002.
 40. Bessler SM , Secor SM . Effects of feeding on luminal pH and morphology of the gastroesophageal junction of snakes. Zoology 115: 319‐329, 2012.
 41. Bjornvad CR , Elnif J , Sangild PT . Short‐term fasting induces intra‐hepatic lipid accumulation and decreases intestinal mass without reduced brush‐border enzyme activity in mink (Mustela vison) small intestine. J Comp Physiol B 174: 625‐632, 2004.
 42. Black D , Love RM . The sequential mobilization and restoration of energy reserves in tissues of Atlantic cod during starvation and refeeding. J Comp Physiol B 156: 469‐479, 1986.
 43. Blasco J , Fernandez J , Gutierrez J . Variations in tissue reserves, plasma metabolites and pancreatic hormones during fasting in immature carp (Cyprinus carpio). Comp Biochem Physiol A 103: 357‐363, 1992.
 44. Boge G , Rigal A , Peres G . A study of invivo glycine absorption by fed and fasted rainbow trout (Salmo gairdneri). J Exp Biol 91: 285‐292, 1981.
 45. Boismenu C , Gauthier G , Larochelle J . Physiology of prolonged fasting in greater snow geese (Chen caerulescens atlantica). Auk 109: 511‐521, 1992.
 46. Booth DT . Effect of soil type on burrowing behavior and cocoon formation in the green‐striped burrowing frog, Cyclorana alboguttata . Can J Zool 84: 832‐838, 2006.
 47. Bouma HR , Carey HV , Kroese FG . Hibernation: The immune system at rest? J Leukoc Biol 88: 619‐624, 2010.
 48. Bourgeon S , Kauffmann M , Geiger S , Raclot T , Robin JP . Relationships between metabolic status, corticosterone secretion and maintenance of innate and adaptive humoral immunities in fasted re‐fed mallards. J Exp Biol 213: 3810‐3818, 2010.
 49. Bourgeon S , Martinez J , Criscuolo F , Le Maho Y , Raclot T . Fasting‐induced changes of immunological and stress indicators in breeding female eiders. Gen Comp Endocrinol 147: 336‐342, 2006.
 50. Bourgeon S , Raclot T . Corticosterone selectively decreases humoral immunity in female eiders during incubation. J Exp Biol 209: 4957‐4965, 2006.
 51. Bourgeon S , Viera VM , RAclot T , Groscolas R . Hormones and immunoglobulin levels in king penguins during moulting and breeding fasts. Ecoscience 14: 519‐528, 2007.
 52. Bowen WD , Boness DJ , Oftedal OT . Mass‐transfer from mother to pup and subsequent mass‐loss by the weaned pup in the hooded seal, Cystophora cristata . Can J Zool 65: 1‐8, 1987.
 53. Bowen WD , Oftedal OT , Boness DJ . Birth to weaning in 4 days ‐ remarkable growth in the hooded seal, Cystophora cristata . Can J Zool 63: 2841‐2846, 1985.
 54. Boyd I , Arnbom T , Fedak M . Water flux, body composition, and metabolic rate during molt in female southern elephant seals (Mirounga leonine). Physiol Zool 66: 43‐60, 1993.
 55. Boyd IL , Lunn NJ , Barton T . Time budgets and foraging characteristics of lactating antarctic fur seals. J Anim Ecol 60: 577‐592, 1991.
 56. Boyer BB , Barnes BM , Lowell BB , Grujic D . Differential regulation of uncoupling protein gene homologues in multiple tissues of hibernating ground squirrels. Am J Physiol Regul Integr Comp Physiol 275: R1232‐R1238, 1998.
 57. Brady LJ , Armstrong MK , Muiruri KL , Romsos DR , Bergen WG , Leveille GA . Influence of prolonged fasting in the dog on glucose turnover and blood metabolites. J Nutr 107: 1053‐1060, 1977.
 58. Bragdon JH , Havel RJ , Gordon RS, Jr . Effects of carbohydrate feeding on serum lipids and lipoproteins in the rat. Am J Physiol 189: 63‐67, 1957.
 59. Brauch KM , Dhruv ND , Hanse EA , Andrews MT . Digital transcriptome analysis indicates adaptive mechanisms in the heart of a hibernating mammal. Physiol Genomics 23: 227‐234, 2005.
 60. Braulke LJ , Heldmaier G , Berriel Diaz M , Rozman J , Exner C . Seasonal changes of myostatin expression and its relation to body mass acclimation in the Djungarian hamster, Phodopus sungorus . J Exp Zool A 313: 548‐556, 2010.
 61. Brooks NE , Myburgh KH , Storey KB . Myostatin levels in skeletal muscle of hibernating ground squirrels. J Exp Biol 214: 2522‐2527, 2011.
 62. Buck CL , Barnes BM . Annual cycle of body composition and hibernation in free‐living arctic ground squirrels. J Mammal 80: 430‐442, 1999.
 63. Buck CL , Barnes BM . Effects of ambient temperature on metabolic rate, respiratory quotient, and torpor in an arctic hibernator. Am J Physiol Regul Integr Comp Physiol 279: R255‐R262, 2000.
 64. Buck MJ , Squire TL , Andrews MT . Coordinate expression of the PDK4 gene: A means of regulating fuel selection in a hibernating mammal. Physiol Genomics 8: 5‐13, 2002.
 65. Burlington RF , Bowers WD , Daum RC , Ashbaugh P . Ultrastructural changes in heart tissue during hibernation. Cryobiology 9: 224‐228, 1972.
 66. Burrin DG , Britton RA , Ferrell CL . Visceral organ size and hepatocyte metabolic activity in fed and fasted rats. J Nutr 118: 1547‐1552, 1988.
 67. Buyse J , Adelsohn DS , Decuypere E , Scanes CG . Diurnal nocturnal changes in food intake, gut storage of ingesta, food transit time and metabolism in growing broiler chickens ‐ a model for temporal control of energy balance. Brit Poult Sci 34: 699‐709, 1993.
 68. Cahill GF, Jr . Fuel metabolism in starvation. Annu Rev Nutr 26: 1‐22, 2006.
 69. Camphuysen CJ , Berrevoets CM , Cremers HJWM , Dekinga A , Dekker R , Ens BJ , van der Have TM , Kats RKH , Kuiken T , Leopold MF , van der Meer J , Piersma T . Mass mortality of common eiders (Somateria mollissima) in the Dutch Wadden Sea, winter 1999/2000: Starvation in a commercially exploited wetland of international importance. Biol Conserv 106: 303‐317, 2002.
 70. Cant JP , McBride BW , Croom WJ, Jr . The regulation of intestinal metabolism and its impact on whole animal energetics. J Anim Sci 74: 2541‐2553, 1996.
 71. Carey HV . Seasonal changes in mucosal structure and function in ground squirrel intestine. Am J Physiol Regul Integr Comp Physiol 259: R385‐R392, 1990.
 72. Carey HV . Effects of fasting and hibernation on ion secretion in ground squirrel intestine. Am J Physiol Regul Integr Comp Physiol 263: R1203‐R1208, 1992.
 73. Carey HV , Frank CL , Seifert JP . Hibernation induces oxidative stress and activation of NK‐κB in ground squirrel intestine. J Comp Physiol B 170: 551‐559, 2000.
 74. Carey HV , Martin SL . Preservation of intestinal gene expression during hibernation. Am J Physiol Gastrointest Liver Physiol 271: G805‐G813, 1996.
 75. Carey HV , Pike AC , Weber CR , Turner JL , Visser A , Beijer‐Liefers SC , Bouma HR , Kroese FGM . Impact of hibernation on gut microbiota and intestinal barrier function in ground squirrels. In: Ruf T , Bieber C , Arnold A , Millesi E , editors. Living in a Seasonal World: Thermoregulatory and Metabolic Adaptations. Heidelberg: Springer, 2012.
 76. Carey HV , Sills NS . Maintenance of intestinal nutrient transport during hibernation. Am J Physiol Regul Integr Comp Physiol 263: R517‐R523, 1992.
 77. Carey HV , Sills NS . Hibernation enhances D‐glucose uptake by intestinal brush border membrane vesicles in ground squirrels. J Comp Physiol B 166: 254‐261, 1996.
 78. Carey HV , Walters WA , Knight R . Seasonal restructuring of the ground squirrel gut microbiota over the annual hibernation cycle. Am J Physiol Regul Integr Comp Physiol 304: R33‐R42, 2013.
 79. Cartledge VA , Withers PC , McMaster KA , Thompson GG , Bradshaw SD . Water balance of field‐excavated aestivating Australian desert frogs, the cocoon‐forming Neobatrachus aquilonius and the non‐cocooning Notaden nichollsi (Amphibia: Myobatrachidae). J Exp Biol 209: 3309‐3321, 2006.
 80. Casey J , Garner J , Garner S , Williard AS . Diel foraging behavior of gravid leatherback sea turtles in deep waters of the Caribbean Sea. J Exp Biol 213: 3961‐3971, 2010.
 81. Castellini JM , Meiselman HJ , Castellini MA . Understanding and interpreting hematocrit measurements in pinnipeds. Mar Mammal Sci 12: 251‐264, 1996.
 82. Castellini MA , Costa DP . Relationships between plasma ketones and fasting duration in neonatal elephant seals. Am J Physiol Regul Integr Comp Physiol 259: R1086‐R1089, 1990.
 83. Castellini MA , Rea LD . The biochemistry of natural fasting at its limits. Experientia 48: 575‐582, 1992.
 84. Castoe TA , de Koning AP , Hall KT , Card DC , Schield DR , Fujita MK , Ruggiero RP , Degner JF , Daza JM , Gu W , Reyes‐Velasco J , Shaney KJ , Castoe JM , Fox SE , Poole AW , Polanco D , Dobry J , Vandewege MW , Li Q , Schott RK , Kapusta A , Minx P , Feschotte C , Uetz P , Ray DA , Hoffmann FG , Bogden R , Smith EN , Chang BS , Vonk FJ , Casewell NR , Henkel CV , Richardson MK , Mackessy SP , Bronikowski AM , Yandell M , Warren WC , Secor SM , Pollock DD . The Burmese python genome reveals the molecular basis for extreme adaptation in snakes. Proc Natl Acad Sci U S A 110: 20645‐20650, 2013.
 85. Caughley G , Grigg GC , Smith L . The effect of drought on kangaroo populations. J Wildlife Manage 49: 679‐685, 1985.
 86. Chakraborty SC , Ross LG , Ross B . Specific dynamic action and feeding metabolism in common carp, Cyprinus carpio L. Comp Biochem Physiol A 103: 809‐815, 1992.
 87. Champagne CD , Crocker DE , Fowler MA , Houser DH . Fasting physiology of the pinnipeds: The challenges of fasting while maintaining high energy expenditure and nutrient delivery for lactation. In: McCue MD , editor. Comparative Physiology of Fasting, Starvation, and Food Limitation. Berlin: Springer‐Verlag, 2012.
 88. Champagne CD , Houser DS , Crocker DE . Glucose metabolism during lactation in a fasting animal, the northern elephant seal. Am J Physiol Regul Integr Comp Physiol 291: R1129‐R1137, 2006.
 89. Chan CR , Lee DN , Cheng YH , Hsieh DJY , Weng CF . Feed deprivation and re‐feeding on alterations of proteases in tilapia Oreochromis mossambicus . Zool Stud 47: 207‐214, 2008.
 90. Chandrasoma PT , Der R , Ma YL , Dalton P , Taira M . Histology of the gastroesophageal junction ‐ an autopsy study. Am J Surg Pathol 24: 402‐409, 2000.
 91. Chatamra K , Daniel PM , Lam DK . The effects of fasting on core temperature, blood glucose and body and organ weights in rats. Q J Exp Physiol 69: 541‐545, 1984.
 92. Chediack JG , Funes SC , Cid FD , Filippa V , Caviedes‐Vidal E . Effect of fasting on the structure and function of the gastrointestinal tract of house sparrows (Passer domesticus). Comp Biochem Physiol A 163: 103‐110, 2012.
 93. Cherel CY , Robin JP , Maho L . Physiology and biochemistry of long‐term fasting in birds. Can J Zool 66: 159‐166, 1988.
 94. Cherel Y , Burnol AF , Leturque A , Le Maho Y . In vivo glucose utilization in rat tissues during the three phases of starvation. Metabolism 37: 1033‐1039, 1988.
 95. Cherel Y , Charrassin JB , Challet E . Energy and protein requirements for molt in the king penguin Aptenodytes patagonicus . Am J Physiol Regul Integr Comp Physiol 266: R1182‐R1188, 1994.
 96. Cherel Y , Charrassin JB , Handrich Y . Comparison of body reserve buildup in prefasting chicks and adults of king penguins (Aptenodytes patagonicus). Physiol Zool 66: 750‐770, 1993.
 97. Cherel Y , Le Maho Y . Five months of fasting in king penguin chicks: Body mass loss and fuel metabolism. Am J Physiol Regul Integr Comp Physiol 249: R387‐R392, 1985.
 98. Cherel Y , Leloup J , Le Maho Y . Fasting in king penguin. II. Hormonal and metabolic changes during molt. Am J Physiol Regul Integr Comp Physiol 254: R178‐R184, 1988.
 99. Cherel Y , Lemaho Y . Metabolic investigations during the initial period of fasting in king penguin chicks. Cr Acad Sci Iii‐Vie 300: 541‐544, 1985.
 100. Cherel Y , Robin JP , Heitz A , Calgari C , Le Maho Y . Relationships between lipid availability and protein utilization during prolonged fasting. J Comp Physiol B 162: 305‐313, 1992.
 101. Cherel Y , Robin JP , Walch O , Karmann H , Netchitailo P , Le Maho Y . Fasting in king penguin. I. Hormonal and metabolic changes during breeding. Am J Physiol Regul Integr Comp Physiol 254: R170‐R177, 1988.
 102. Cherel Y , Stahl JC , Lemaho Y . Ecology and physiology of fasting in king penguin chicks. Auk 104: 254‐262, 1987.
 103. Chew SF , Chan NK , Loong AM , Hiong KC , Tam WL , Ip YK . Nitrogen metabolism in the African lungfish (Protopterus dolloi) aestivating in a mucus cocoon on land. J Exp Biol 207: 777‐786, 2004.
 104. Christel CM , DeNardo DF , Secor SM . Metabolic and digestive response to food ingestion in a binge‐feeding lizard, the Gila monster (Heloderma suspectum). J Exp Biol 210: 3430‐3439, 2007.
 105. Christian K . Some physiological consequences of estivation by freshwater crocodilians, Crocodylus johnstoni . J Herpetol 30: 1‐9, 1996.
 106. Christian KA , Baudinette RV , Pamula Y . Energetic costs of activity by lizards in the field. Funct Ecol 11: 392‐397, 1997.
 107. Clapham P. Whales of the World. Hong Kong: Voyageur Press, 1997.
 108. Cohen AA , Martin LB , Wingfield JC , McWilliams SR , Dunne JA . Physiological regulatory networks: Ecological roles and evolutionary constraints. Trends Ecol Evol 27: 428‐435, 2012.
 109. Concannon P , Levac K , Rawson R , Tennant B , Bensadoun A . Seasonal changes in serum leptin, food intake, and body weight in photoentrained woodchucks. Am J Physiol Regul Integr Comp Physiol 281: R951‐R959, 2001.
 110. Corben CJ , Ingram GJ , Tyler MJ . Gastric brooding ‐ unique form of parental care in an australian frog. Science 186: 946‐947, 1974.
 111. Corssmit EP , Romijn JA , Sauerwein HP . Regulation of glucose production with special attention to nonclassical regulatory mechanisms: A review. Metabolism 50: 742‐755, 2001.
 112. Costa DP , Ortiz CL . Blood chemistry homeostasis during prolonged fasting in the northern elephant seal. Am J Physiol Regul Integr Comp Physiol 242: R591‐R595, 1982.
 113. Costello EK , Gordon JI , Secor SM , Knight R . Postprandial remodeling of the gut microbiota in Burmese pythons. ISME J 4: 1375‐1385, 2010.
 114. Cott HB . Scientific results of an inquiry into the ecology and economic status of the Nile crocodile (Crocodilus niloticus) in Uganda and Northern Rhodesia. Trans Zool Soc London 29: 211‐356, 1961.
 115. Cotton CJ , Harlow HJ . Avoidance of skeletal muscle atrophy in spontaneous and facultative hibernators. Physiol Biochem Zool 83: 551‐560, 2010.
 116. Cowan JS , Schachter D , Hetenyi G, Jr . Validity of a tracer‐injection method for studying glucose turnover in normal dogs. J Nucl Med 10: 98‐102, 1969.
 117. Cowan KJ , Storey KB . Reversible phosphorylation control of skeletal muscle pyruvate kinase and phosphofructokinase during estivation in the spadefoot toad, Scaphiopus couchii . Mol Cell Biochem 195: 173‐181, 1999.
 118. Cox CL , Secor SM . Matched regulation of gastrointestinal performance in the Burmese python, Python molurus . J Exp Biol 211: 1131‐1140, 2008.
 119. Cox CL , Secor SM . Integrated postprandial responses of the diamondback water snake, Nerodia rhomibifer . Physiol Biochem Zool 83: 618‐631, 2010.
 120. Cramp RL , Franklin CE , Meyer EA . The impact of prolonged fasting during aestivation on the structure of the small intestine in the green‐striped burrowing frog, Cyclorana alboguttata . Acta Zool 86: 13‐24, 2005.
 121. Crawford PA , Crowley JR , Sambandam N , Muegge BD , Costello EK , Hamady M , Knight R , Gordon JI . Regulation of myocardial ketone body metabolism by the gut microbiota during nutrient deprivation. Proc Natl Acad Sci U S A 106: 11276‐11281, 2009.
 122. Crocker DE , Costa DP . Pinniped Physiology. In: Perrin WF , Wursig B , Thewissen JGM , editors. The Encyclopedia of Marine Mammals. New York: Academic Press, 2008, pp. 873‐878.
 123. Crocker DE , Webb PM , Costa DP , Le Boeuf BJ . Protein catabolism and renal function in lactating northern elephant seals. Physiol Zool 71: 485‐491, 1998.
 124. da Silva RSM , Migliortni RH . Effects of starvation and refeeding on energy‐linked metabolic processes in the turtle (Phrynops hilarii). Comp Biochem Physiol Part A 3: 415–419, 1990.
 125. Dallman MF , Strack AM , Akana SF , Bradbury MJ , Hanson ES , Scribner KA , Smith M . Feast and famine: Critical role of glucocorticoids with insulin in daily energy flow. Front Neuroendocrinol 14: 303‐347, 1993.
 126. Dark J . Annual lipid cycles in hibernators: Integration of physiology and behavior. Ann Rev Nutr 25: 469‐497, 2005.
 127. Dausmann KH , Glos J , Ganzhorn JU , Heldmaier G . Physiology: Hibernation in a tropical primate. Nature 429: 825‐826, 2004.
 128. Dave G , Johansson‐Sjöbeck ML , Larsson Å , Lewander K , Lidman U . Metabolic and hematological effects of starvation in the european eel, Anguilla anguilla L.–III. Fatty acid composition. Comp Biochem Physiol B 53: 509‐515, 1976.
 129. Dave G , Johansson‐Sjöbeck ML , Larsson Å , Lewander K , Lidman U . Metabolic and hematological effects of starvation in european eel, Anguilla‐Anguilla L .1. carbohydrate, lipid, protein and inorganic ion metabolism. Comp Biochem Physiol A 52: 423‐430, 1975.
 130. David LA , Maurice CF , Carmody RN , Gootenberg DB , Button JE , Wolfe BE , Ling AV , Devlin AS , Varma Y , Fischbach MA , Biddinger SB , Dutton RJ , Turnbaugh PJ . Diet rapidly and reproducibly alters the human gut microbiome. Nature 505: 559‐563, 2014.
 131. Day R , Tibbetts IR , Secor SM . Physiological responses to short‐term fasting among herbivorous, omnivorous, and carnivorous fishes. J Comp Physiol B 184: 497‐512, 2014.
 132. De Pedro N , Delgado MJ , Alonso‐Bedate M . Fasting and hypothalamic catecholamines in goldfish. J Fish Biol 58: 1404‐1413, 2001.
 133. De Pedro N , Delgado MJ , Gancedo B , Alonso‐Bedate M . Changes in glucose, glycogen, thyroid activity and hypothalamic catecholamines in tench by starvation and refeeding. J Comp Physiol B 173: 475‐481, 2003.
 134. de Souza SCR , de Carvalho JE , Abe AS , Bicudo JEPW , Bianconcini MSC . Seasonal metabolic depression, substrate utilization and changes in scaling patterns during the first year cycle of tegu lizards (Tupinambis merianae). J Exp Biol 207: 307‐318, 2004.
 135. Delaney RG , Lahiri S , Fishman AP . Aestivation of the African lungfish Protopterus aethiopicus: Cardiovascular and respiratory functions. J Exp Biol 61: 111‐128, 1974.
 136. Delgiudice GD , Seal US , Mech LD . Effects of feeding and fasting on wolf blood and urine characteristics. J Wildlife Manage 51: 1‐10, 1987.
 137. Demeneix BA , Henderson NE . Serum T4 and T3 in active and torpid ground squirrels, Spermophilus richardsoni . Gen Comp Endocrinol 35: 77‐85, 1978.
 138. Demeneix BA , Henderson NE . Thyroxine metabolism in active and torpid ground squirrels, Spermophilus richardsoni . Gen Comp Endocrinol 35: 86‐92, 1978.
 139. Deraniyagala P . The tetrapod reptiles of Ceylon. Ceylon J Sci Biol Sci 412: 1939, 1939.
 140. Derrien M , Vaughan EE , Plugge CM , de Vos WM . Akkermansia muciniphila gen. nov., sp. nov., a human intestinal mucin‐degrading bacterium. Int J Syst Evol Microbiol 54: 1469‐1476, 2004.
 141. Deutsch CJ , Crocker DE , Costa DP , Le Boeuf BJ . Sex and age‐related variation in reproductive effort in northern elephant seals. In: Le Boeuf BJ , Laws RM , editors. Elephant Seals: Population Ecology, Behavior, and Physiology. Berkeley: University of California Press, 1994, pp. 169‐210.
 142. Dewasmes G , Le Maho Y , Cornet A , Groscolas R . Resting metabolic rate and cost of locomotion in long‐term fasting emperor penguins. J Appl Physiol, Resp, Environm Exercise Physiol 49: 888‐896, 1980.
 143. Didier R , Remesy C , Demigne C . Changes in glucose and lipid metabolism in starved or starved‐refed Japanese quail (Coturnix coturnix japonica) in relation to fine structure of liver cells. Comp Biochem Physiol A 74: 839‐848, 1983.
 144. Dill‐McFarland KA , Neil KL , Zeng A , Sprenger RJ , Kurtz CC , Suen G , Carey HV . Hibernation alters the diversity and composition of mucosa‐associated bacteria while enhancing antimicrobial defence in the gut of 13‐lined ground squirrels. Mol Ecol 23: 4658–4669, 2014.
 145. Dingle H. Migration: The Biology of Life on the Move: Oxford University Press, 1996.
 146. Dorrestein PC , Mazmanian SK , Knight R . Finding the missing links among metabolites, microbes, and the host. Immunity 40: 824‐832, 2014.
 147. Duchamp C , Barre H , Rouanet JL , Lanni A , Cohenadad F , Berne G , Brebion P . Nonshivering thermogenesis in king penguin chicks .1. Role of skeletal‐muscle. Am J Physiol Regul Integr Comp Physiol 261: R1438‐R1445, 1991.
 148. Duchamp C , Barre H , Rouanet JL , Lanni A , Cohenadad F , Berne G , Brebion P . Nonshivering thermogenesis in king penguin chicks. 2. effect of fasting. Am J Physiol Regul Integr Comp Physiol 261: R1446‐R1454, 1991.
 149. Dunel‐Erb S , Chevalier C , Laurent P , Bach A , Decrock F , Le Maho Y . Restoration of the jejunal mucosa in rats refed after prolonged fasting. Comp Biochem Physiol A 129: 933‐947, 2001.
 150. Eddy SF , Storey KB . Differential expression of Akt, PPARgamma, and PGC‐1 during hibernation in bats. Biochem Cell Biol 81: 269‐274, 2003.
 151. Elvert R , Heldmaier G . Cardiorespiratory and metabolic reactions during entrance into torpor in dormice, Glis glis . J Exp Biol 208: 1373‐1383, 2005.
 152. Emadi Shaibani M , Mojazi Amiri B , Khodabandeh S . Starvation and refeeding effects on pyloric caeca structure of Caspian salmon (Salmo trutta caspius, Kessler 1877) juvenile. Tissue Cell 45: 204‐210, 2013.
 153. Epperson LE , Dahl TA , Martin SL . Quantitative analysis of liver protein expression during hibernation in the golden‐mantled ground squirrel. Mol Cell Proteomics 3: 920‐933, 2004.
 154. Epperson LE , Karimpour‐Fard A , Hunter LE , Martin SL . Metabolic cycles in a circannual hibernator. Physiol Genomics 43: 799‐807, 2011.
 155. Epperson LE , Martin SL . Quantitative assessment of ground squirrel mRNA levels in multiple stages of hibernation. Physiol Genomics 10: 93‐102, 2002.
 156. Epperson LE , Rose JC , Carey HV , Martin SL . Seasonal proteomic changes reveal molecular adaptations to preserve and replenish liver proteins during ground squirrel hibernation. Am J Physiol Regul Integr Comp Physiol 298: R329‐R340, 2010.
 157. Errington PR . The comparative ability of the bob‐white and the ring‐necked pheasant to withstand cold and hunger. Wilson Bull 51: 22‐37, 1939.
 158. Esher RJ , Fleischman AI , Lenz PH . Blood and liver lipids in torpid and aroused little brown bats, Myotis lucifugus . Comp Biochem Physiol A 45: 933‐938, 1973.
 159. Etheridge K . The energetics of estivating sirenid salamanders (Siren lacertina and Pseudobranchus striatus). Herpetologica 46: 407‐414, 1990.
 160. Etheridge K . Water‐balance in estivating sirenid salamanders (Siren lacertina). Herpetologica 46: 400‐406, 1990.
 161. Evans GS , Potten CS . The distribution of endocrine cells along the mouse intestine: A quantitative immunocytochemical study. Virchows Archiv 56: 191‐199, 1988.
 162. Evans P . The Natural History of Whales and Dolphins. New York, USA: Facts on File Publications, 1987.
 163. Even PC , Bertin E , Gangnerau MN , Roseau S , Tome D , Portha B . Energy restriction with protein restriction increases basal metabolism and meal‐induced thermogenesis in rats. Am J Physiol Regul Integr Comp Physiol 284: R751‐R759, 2003.
 164. Fahlman A , Storey JM , Storey KB . Gene up‐regulation in heart during mammalian hibernation. Cryobiology 40: 332‐342, 2000.
 165. Falkenstein F , Kortner G , Watson K , Geiser F . Dietary fats and body lipid composition in relation to hibernation in free‐ranging echidnas. J Comp Physiol B 171: 189‐194, 2001.
 166. Fanning JC , Tyler MJ , Shearman DJ . Converting a stomach to a uterus: The microscopic structure of the stomach of the gastric brooding frog Rheobatrachus silus . Gastroenterology 82: 62‐70, 1982.
 167. Farley SD , Robbins CT . Lactation, hibernation, and mass dynamics of American black bears and grizzly bears. Can J Zool 73: 2216‐2222, 1995.
 168. Fedorov VB , Goropashnaya AV , Toien O , Stewart NC , Chang C , Wang H , Yan J , Showe LC , Showe MK , Barnes BM . Modulation of gene expression in heart and liver of hibernating black bears (Ursus americanus). BMC Genomics 12: 171, 2011.
 169. Fedorov VB , Goropashnaya AV , Toien O , Stewart NC , Chang C , Wang H , Yan J , Showe LC , Showe MK , Donahue SW , Barnes BM . Preservation of bone mass and structure in hibernating black bears (Ursus americanus) through elevated expression of anabolic genes. Funct Integr Genomics 12: 357‐365, 2012.
 170. Fedorov VB , Goropashnaya AV , Toien O , Stewart NC , Gracey AY , Chang C , Qin S , Pertea G , Quackenbush J , Showe LC , Showe MK , Boyer BB , Barnes BM . Elevated expression of protein biosynthesis genes in liver and muscle of hibernating black bears (Ursus americanus). Physiol Genomics 37: 108‐118, 2009.
 171. Felig P , Owen OE , Wahren J , Cahill GF, Jr . Amino acid metabolism during prolonged starvation. J Clin Invest 48: 584‐594, 1969.
 172. Ferraris RP , Carey HV . Intestinal transport during fasting and malnutrition. Annu Rev Nutr 20: 195‐219, 2000.
 173. Fietz J , Tataruch F , Dausmann KH , Ganzhorn JU . White adipose tissue composition in the free‐ranging fat‐tailed dwarf lemur (Cheirogaleus medius; Primates), a tropical hibernator. J Comp Physiol B 173: 1‐10, 2003.
 174. Figueiredo‐Garutti ML , Navarro I , Capilla E , Souza RH , Moraes G , Gutierrez J , Vicentini‐Paulino ML . Metabolic changes in Brycon cephalus (Teleostei, Characidae) during post‐feeding and fasting. Comp Biochem Physiol A 132: 467‐476, 2002.
 175. Finn PF , Dice JF . Proteolytic and lipolytic responses to starvation. Nutrition 22: 830‐844, 2006.
 176. Fishman AP , Pack AI , Delaney RG , Galante RJ . Estivation in Protopterus . J Morphol 1: 237‐248, 1986.
 177. Fleck CC , Carey HV . Modulation of apoptotic pathways in intestinal mucosa during hibernation. Am J Physiol Regul Integr Comp Physiol 289: R586‐R595, 2005.
 178. Florant GL , Fenn AM , Healy JE , Wilkerson GK , Handa RJ . To eat or not to eat: The effect of AICAR on food intake regulation in yellow‐bellied marmots (Marmota flaviventris). J Exp Biol 213: 2031‐2037, 2010.
 179. Florant GL , Healy JE . The regulation of food intake in mammalian hibernators: A review. J Comp Physiol B 182: 451‐467, 2012.
 180. Florant GL , Nuttle LC , Mullinex DE , Rintoul DA . Plasma and white adipose tissue lipid composition in marmots. Am J Physiol Regul Integr Comp Physiol 258: 1123‐1131, 1990.
 181. Florant GL , Porst H , Peiffer A , Hudachek SF , Pittman C , Summers SA , Rajala MW , Scherer PE . Fat‐cell mass, serum leptin and adiponectin changes during weight gain and loss in yellow‐bellied marmots (Marmota flaviventris). J Comp Physiol B 174: 633‐639, 2004.
 182. Fon Tacer K , Kuzman D , Seliskar M , Pompon D , Rozman D . TNF‐alpha interferes with lipid homeostasis and activates acute and proatherogenic processes. Physiol Genomics 31: 216‐227, 2007.
 183. Ford DJ . Effect of microflora on gastrointestinal pH in chick. Brith Poult Sci 15: 131‐140, 1974.
 184. Foster GD , Moon TW . Hypometabolism with fasting in the yellow perch (Perca flavescens) ‐ a study of enzymes, hepatocyte metabolism, and tissue size. Physiol Zool 64: 259‐275, 1991.
 185. Fox AM , Musacchia XJ . Notes on the pH of the digestive tract of Chrysemys picta . Copeia 1950: 337‐339, 1950.
 186. Freitas MB , Goulart LS , Barros MS , Morais DB , Amaral TS , Matta SL . Energy metabolism and fasting in male and female insectivorous bats Molossus molossus (Chiroptera: Molossidae). Brazilian J Biol 70: 617‐621, 2010.
 187. Freitas MB , Welker AF , Millan SF , Pinheiro EC . Metabolic responses induced by fasting in the common vampire bat Desmodus rotundus . J Comp Physiol B 173: 703‐707, 2003.
 188. Frerichs KU , Smith CB , Brenner M , DeGracia DJ , Krause GS , Marrone L , Dever TE , Hallenbeck JM . Suppression of protein synthesis in brain during hibernation involves inhibition of protein initiation and elongation. Proc Natl Acad Sci 95: 14511‐14516, 1998.
 189. Frick NT , Bystriansky JS , Ip YK , Chew SF , Ballantyne JS . Carbohydrate and amino acid metabolism in fasting and aestivating African lungfish (Protopterus dolloi). Comp Biochem Physiol A 151: 85‐92, 2008.
 190. Frick NT , Bystriansky JS , Ip YK , Chew SF , Ballantyne JS . Lipid, ketone body and oxidative metabolism in the African lungfish, Protopterus dolloi following 60 days of fasting and aestivation. Comp Biochem Physiol A 151: 93‐101, 2008.
 191.Friedman MHF, Armour JC . Gastric secretion in the groundhog (Marmota monax) during hibernation. J Cell Comp Physiol 8: 201‐211, 1936.
 192. Fuery CJ , Withers PC , Hobbs AA , Guppy M . The role of protein synthesis during metabolic depression in the Australian desert frog Neobatrachus centralis . Comp Biochem Physiol A 119: 469‐476, 1998.
 193. Fuglei E , Aanestad M , Berg JP . Hormones and metabolites of arctic foxes (Alopex lagopus) in response to season, starvation and re‐feeding. Comp Biochem Physiol A 126: 287‐294, 2000.
 194. Furne M . Effect of starvation and refeeding on digestive enzyme activities in sturgeon (Acipenser naccarii) and trout (Oncorhynchus mykiss). Comp Biochem Physiol A 149: 420‐425, 2008.
 195. Furne M , Morales AE , Trenzado CE , Garcia‐Gallego M , Hidalgo MC , Domezain A , Rus AS . The metabolic effects of prolonged starvation and refeeding in sturgeon and rainbow trout. J Comp Physiol B 182: 63‐76, 2012.
 196. Galluser M , Raul F , Canguilhem B . Adaptation of intestinal enzymes to seasonal and dietary changes in a hibernator: The European hamster (Cricetus cricetus). J Comp Physiol B 158: 143‐149, 1988.
 197. Galster W , Morrison P . Seasonal changes in body composition of the artic ground squirrel, Citellus undulatus . Can J Zool 54: 74‐78, 1975.
 198. Galster W , Morrison PR . Gluconeogenesis in arctic ground squirrels between periods of hibernation. Am J Physiol 228: 325‐330, 1975.
 199. Galster WA , Morrison P . Cyclic changes in carbohydrate concentrations during hibernation in the arctic ground squirrel. Am J Physiol 218: 1228‐1232, 1970.
 200. Gao YF , Wang J , Wang HP , Feng B , Dang K , Wang Q , Hinghofer‐Szalkay HG . Skeletal muscle is protected from disuse in hibernating dauria ground squirrels. Comp Biochem Physiol A 161: 296‐300, 2012.
 201. Garcia‐Rodriguez T , Ferrer M , Carrillo JC , Castroviejo J . Metabolic responses of Buteo buteo to long‐term fasting and refeeding. Comp Biochem Physiol A 87: 381‐386, 1987.
 202. Gas N , Noailliac‐Depeyre J . Studies on intestinal epithelium involution during prolonged fasting. J Ultrastr Res 56: 137‐151, 1976.
 203. Gaucher L , Vidal N , D'Anatro A , Naya DE . Digestive flexibility during fasting in the characid fish Hyphessobrycon luetkenii . J Morphol 273: 49‐56, 2012.
 204. Gauthier‐Clerc M , Le Maho Y , Clerquin Y , Bost CA , Handrich Y . Seabird reproduction in an unpredictable environment: How King penguins provide their young chicks with food. Mar Ecol Prog Ser 237: 291‐300, 2002.
 205. Gauthier‐Clerc M , Le Maho Y , Clerquin Y , Drault S , Handrich Y . Ecophysiology ‐ penguin fathers preserve food for their chicks. Nature 408: 928‐929, 2000.
 206. Gaylord TG , MacKenzie DS , Gatlin DM . Growth performance, body composition and plasma thyroid hormone status of channel catfish (Ictalurus punctatus) in response to short‐term feed deprivation and refeeding. Fish Physiol Biochem 24: 73‐79, 2001.
 207. Gehlbach FR , Gordon R , Jordan JB . Estivation of salamander, Siren intermedia . Am Midl Natur 89: 455‐463, 1973.
 208. Geiser F . Metabolic rate and body temperature reduction during hibernation and daily torpor. Annu Rev Physiol 66: 239‐274, 2004.
 209. Geiser F . Yearlong hibernation in a marsupial mammal. Naturwissenschaften 94: 941‐944, 2007.
 210. Geiser F . Aestivation in mammals and birds. Prog Mol Subcell Biol 49: 95‐111, 2010.
 211. Gentry R , Kooyman G , Goebel M . Feeding and Diving Behavior of Northern Fur Seals. Princeton, New Jersey, USA: Princeton University Press, 1986.
 212. Georges JY , Guinet C . Maternal care in the subantarctic fur seals on Amsterdam Island. Ecology 81: 295‐308, 2000.
 213. German DP , Neuberger DT , Callahan MN , Lizardo NR , Evans DH . Feast to famine: The effects of food quality and quantity on the gut structure and function of a detritivorous catfish (Teleostei: Loricariidae). Comp Biochem Physiol A 155: 281‐293, 2010.
 214. Giambrone TP , Lignot JH , Secor SM , Frederick J . Maintenance of digestive performance is ontogenetically stable for the American alligator. Integr Comp Biol 49: E234‐E234, 2009.
 215. Gilbert SF , Sapp J , Tauber AI . A symbiotic view of life: We have never been individuals. Quart Rev Biol 87: 325‐341, 2012.
 216. Gist DH . Effects of starvation and refeeding on carbohydrate and lipid reserves of Anolis carolinensis . Comp Biochem Physiol A 43: 771‐780, 1972.
 217. Gluck EF , Stephens N , Swoap SJ . Peripheral ghrelin deepens torpor bouts in mice through the arcuate nucleus neuropeptide Y signaling pathway. Am J Physiol Regul Integr Comp Physiol 291: R1303‐R1309, 2006.
 218. Goodman MN , Ruderman NB . Starvation in the rat. I. Effect of age and obesity on organ weights, RNA, DNA, and protein. Am J Physiol Endocrinol Metab 239: E269‐E276, 1980.
 219. Grabek KR , Karimpour‐Fard A , Epperson LE , Hindle A , Hunter LE , Martin SL . Multistate proteomics analysis reveals novel strategies used by a hibernator to precondition the heart and conserve ATP for winter heterothermy. Physiol Genomics 43: 1263‐1275, 2011.
 220. Grabek KR , Martin SL , Hindle AG . Proteomics approaches shed new light on hibernation physiology. J Comp Physiol B 185: 607‐627, 2015.
 221. Grably S , Piery Y . Weight and tissue changes in long‐term starved frogs Rana esculenta . Comp Biochem Physiol A 69: 683‐688, 1981.
 222. Greene HW . Snakes: The Evolution of Mystery in Nature. Berkeley: University of California Press, 1997.
 223. Greenwood P. The Natural History of African Lungfishes. New York, 1987.
 224. Gregory P . Reptilian hibernation. In: Gans C , Pough FH , editors. Biology of the Reptilia. London: Academic Press, 1982, pp. 53‐154.
 225. Gromme O . Effects of extreme cold on ducks in Milwaukee Bay. Auk 53: 324‐325, 1936.
 226. Groscolas R . Changes in body mass, body temperature and plasma fuel levels during the natural breeding fast in male and female Emperor penguins Aptenodytes forsteri . J Comp Physiol B 156: 521‐527, 1986.
 227. Groscolas R , Charpentier C , Lemonnier F . Variation in free amino acid concentration in plasma during the reproductive cycle in the emperor penguin (Aptenodytes forsteri). Comp Biochem Physiol B 51: 57‐67, 1975.
 228. Groscolas R , Cherel Y . How to molt while fasting in the cold: The metabolic and hormonal adaptations of emperor and king penguins. Ornis Scandinavica 23: 328‐334 1992.
 229. Groscolas R , Herzberg GR . Fasting‐induced selective mobilization of brown adipose tissue fatty acids. J Lipid Res 38: 228‐238, 1997.
 230. Groscolas R , Robin JP . Long‐term fasting and re‐feeding in penguins. Comp Biochem Physiol A 128: 645‐655, 2001.
 231. Groscolas R , Rodriguez A . Glucose and lactate kinetics and interrelations in an antarctic bird (emperor penguin). Am J Physiol Regul Integr Comp Physiol 242: R458‐R464, 1982.
 232. Guppy M , Withers P . Metabolic depression in animals: Physiological perspectives and biochemical generalizations. Biol Rev 74: 1‐40, 1999.
 233. Gutierrez J , Perez J , Navarro I , Zanuy S , Carrillo M . Changes in plasma‐glucagon and insulin associated with fasting in sea bass (Dicentrarchus labrax). Fish Physiol Biochem 9: 107‐112, 1991.
 234. Gutierrez J , Plisetskaya EM . Insulin binding to liver plasma membranes of coho salmon during smoltification. Gen Comp Endocrinol 82: 466‐475, 1991.
 235. Gygi SP , Rochon Y , Franza BR , Aebersold R . Correlation between protein and mRNA abundance in yeast. Mol Cell Biol 19: 1720‐1730, 1999.
 236. Habold C , Chevalier C , Dunel‐Erb S , Foltzer‐Jourdainne C , Le Maho Y , Lignot JH . Effects of fasting and refeeding on jejunal morphology and cellular activity in rats in relation to depletion of body stores. Scand J Gastroenterol 39: 531‐539, 2004.
 237. Hainsworth FR , Collins BG , Wolf LL . Function of torpor in hummingbirds. Physiol Zool 50: 215‐222, 1977.
 238. Hampton M , Melvin RG , Andrews MT . Transcriptomic analysis of brown adipose tissue across the physiological extremes of natural hibernation. PLoS One 8: e85157, 2013.
 239. Hampton M , Melvin RG , Kendall AH , Kirkpatrick BR , Peterson N , Andrews MT . Deep sequencing the transcriptome reveals seasonal adaptive mechanisms in a hibernating mammal. PLoS One 6: e27021, 2011.
 240. Handrich Y , Nicolas L , Lemaho Y . Winter starvation in captive common barn owls ‐ bioenergetics during refeeding. Auk 110: 470‐480, 1993.
 241. Handrich Y , Nicolas L , Lemaho Y . Winter starvation in captive common barn owls ‐ physiological states and reversible limits. Auk 110: 458‐469, 1993.
 242. Hanna MY . Effect of starvation on carbohydrate content of tissues and on relative weights of organs of Clarius lazera . Zeit Verg Physiol 45: 315‐321, 1962.
 243. Hardie DG , Ross FA , Hawley SA . AMPK: A nutrient and energy sensor that maintains energy homeostasis. Nat Rev Mol Cell Biol 13: 251‐262, 2012.
 244. Harlow H . Muscle protein and strength retention by bears during winter fasting and starvation. In: McCue MD , editor. Comparative Physiology of Fasting, Starvation and Food Limitation. Heidelberg: Springer‐Verlag, 2012, pp. 277‐296.
 245. Harlow HJ . Fasting biochemistry of representative spontaneous and facultative hibernators: The white‐tailed prairie dog and the black‐tailed prairie dog. Physiol Zool 68: 915‐934, 1995.
 246. Harlow HJ , Beck TD , Greenhouse S , Walters LM . Seasonal serum glucose, progesterone, and cortisol levels of black bears (Ursus americanus). Can J Zool 68: 183‐187, 1990.
 247. Harlow HJ , Buskirk SW . Comparative plasma and urine chemistry of fasting white‐tailed prairie dogs (Cynomys leucurus) and American martens (Martes americana) ‐ representative fat‐bodied and lean‐bodied animals. Physiol Zool 64: 1262‐1278, 1991.
 248. Harlow HJ , Lohuis T , Grogan RG , Beck TDI . Body mass and lipid changes by hibernating reproductive and nonreproductive black bears (Ursus americanus). J Mammal 83: 1020‐1025, 2002.
 249. Harlow HJ , Menkens GE . A comparison of hibernation in the black‐tailed prairie dog, white‐tailed prairie dog, and Wyoming ground squirrel. Can J Zool 64: 793‐796, 1985.
 250. Harlow HJ , Seal US . Changes in hematology and metabolites in the serum and urine of the badger, Taxidea taxus, during food deprivation. Can J Zool 59: 2123‐2128, 1981.
 251. Hays GC , Broderick AC , Glen F , Godley BJ . Change in body mass associated with long‐term fasting in a marine reptile: The case of green turtles (Chelonia mydas) at Ascension Island. Can J Zool 80: 1299‐1302, 2002.
 252. Healy JE , Bateman JL , Ostrom CE , Florant GL . Peripheral ghrelin stimulates feeding behavior and positive energy balance in a sciurid hibernator. Horm Behav 59: 512‐519, 2011.
 253. Healy JE , Gearhart CN , Bateman JL , Handa RJ , Florant GL . AMPK and ACCchange with fasting and physiological condition in euthermic and hibernating golden‐mantled ground squirrels (Callospermophilus lateralis). Comp Biochem Physiol A 159: 322‐331, 2011.
 254. Healy JE , Ostrom CE , Wilkerson GK , Florant GL . Plasma ghrelin concentrations change with physiological state in a sciurid hibernator (Spermophilus lateralis). Gen Comp Endocrinol 166: 372‐378, 2010.
 255. Heldmaier G , Ortmann S , Elvert R . Natural hypometabolism during hibernation and daily torpor in mammals. Respir Physiol Neurobiol 141: 317‐329, 2004.
 256. Heldmaier G , Ruf T . Body temperature and metabolic rate during natural hypothermia in endotherms. J Comp Physiol B 162: 696‐706, 1992.
 257. Helmstetter C , Reix N , T'Flachebba M , Pope RK , Secor SM , Le Maho Y , Lignot JH . Functional changes with feeding in the gastro‐intestinal epithelia of the Burmese python (Python molurus). Zoolog Sci 26: 632‐638, 2009.
 258. Hemmings SJ , Storey KB . Characterization of gamma‐glutamyltranspeptidase in the liver of the frog: 3. Response to freezing and thawing in the freeze‐tolerant wood frog Rana sylvatica . Cell Biochem Funct 14: 139‐148, 1996.
 259. Hemre GI , Lie O , Sundby A . Dietary carbohydrate utilization in cod (Gadus morhua) ‐ metabolic responses to feeding and fasting. Fish Physiol Biochem 10: 455‐463, 1993.
 260. Henry K , Magee H , Reid E . Some effects of fasting on the composition of the blood and respiratory exchange in fowls. J Exp Biol 11: 58‐72, 1934.
 261. Hervant F , Mathieu J , Durand J . Behavioural, physiological and metabolic responses to long‐term starvation and refeeding in a blind cave‐dwelling (Proteus anguinus) and a surface‐dwelling (Euproctus asper) salamander. J Exp Biol 204: 269‐281, 2001.
 262. Hindle AG , Grabek KR , Epperson LE , Karimpour‐Fard A , Martin SL . Metabolic changes associated with the long winter fast dominate the liver proteome in 13‐lined ground squirrels. Physiol Genomics 46: 348‐361, 2014.
 263. Hindle AG , Karimpour‐Fard A , Epperson LE , Hunter LE , Martin SL . Skeletal muscle proteomics: Carbohydrate metabolism oscillates with seasonal and torpor‐arousal physiology of hibernation. Am J Physiol Regul Integr Comp Physiol 301: R1440‐R1452, 2011.
 264. Hindle AG , Martin SL . Intrinsic circannual regulation of brown adipose tissue form and function in tune with hibernation. Am J Physiol Endocrinol Metab 306: E284‐E299, 2014.
 265. Hindle AG , Otis JP , Epperson LE , Hornberger TA , Goodman CA , Carey HV , Martin SL . Prioritization of skeletal muscle growth for emergence from hibernation. J Exp Biol 218: 276‐284, 2015.
 266. Hissa R , Hohtola E , Tuomala‐Saramaki T , Laine T , Kallio H . Seasonal changes in fatty acids and leptin contents in the plasma of the European brown bear (Ursus arctos arctos). Ann Zool Fennici 35: 215‐224, 1998.
 267. Hissa R , Siekkinen J , Hohtola E , Saarela S , Hakala A , Pudas J . Seasonal patterns in the physiology of the European brown bear (Ursus arctos arctos) in Finland. Comp Biochem Physiol A 109: 781‐791, 1994.
 268. Hochachka PW , Somero GN . Biochemical Adaptation: Mechanism and Process in Physiological Evolution. New York: Oxford University Press, 2002.
 269. Hoehn KL , Hudachek SF , Summers SA , Florant GL . Seasonal, tissue‐specific regulation of Akt/protein kinase B and glycogen synthase in hibernators. Am J Physiol Regul Integr Comp Physiol 286: R498‐R504, 2004.
 270. Horman S , Hussain N , Dilworth SM , Storey KB , Rider MH . Evaluation of the role of AMP‐activated protein kinase and its downstream targets in mammalian hibernation. Comp Biochem Physiol B 142: 374‐382, 2005.
 271. Horst K , Mendel LB , Benedict FG . The metabolism of the albino rat during prolonged fasting at two different environmental temperatures. J Nutr 3: 177‐200, 1930.
 272. Houser DS , Champagne CD , Crocker DE . Lipolysis and glycerol gluconeogenesis in simultaneously fasting and lactating northern elephant seals. Am J Physiol Regul Integr Comp Physiol 293: R2376‐R2381, 2007.
 273. Houser DS , Costa DP . Protein catabolism in suckling and fasting northern elephant seal pups (Mirounga angustirostris). J Comp Physiol B 171: 635‐642, 2001.
 274. Hudson NJ , Franklin CE . Effect of aestivation on muscle characteristics and locomotor performance in the Green‐striped burrowing frog, Cyclorana alboguttata . J Comp Physiol B 172: 177‐182, 2002.
 275. Hudson NJ , Lavidis NA , Choy PT , Franklin CE . Effect of prolonged inactivity on skeletal motor nerve terminals during aestivation in the burrowing frog, Cyclorana alboguttata . J Comp Physiol A 191: 373‐379, 2005.
 276. Hudson NJ , Lehnert SA , Ingham AB , Symonds B , Franklin CE , Harper GS . Lessons from an estivating frog: Sparing muscle protein despite starvation and disuse. Am J Physiol Reg Integr Comp Physiol 290: R836‐R843, 2006.
 277. Hume ID , Beiglbock C , Ruf T , Frey‐Roos F , Bruns U , Arnold W . Seasonal changes in morphology and function of the gastrointestinal tract of free‐living alpine marmots (Marmota marmota). J Comp Physiol B 172: 197‐207, 2002.
 278. Humphries MM , Thomas DW , Kramer DL . The role of energy availability in mammalian hibernation: A cost‐benefit approach. Physiol Biochem Zool 76: 165‐179, 2003.
 279. Hurst T . Causes and consequences of winter mortality in fishes. J Fish Biol 71: 315‐345, 2007.
 280. Icardo JM , Amelio D , Garofalo F , Colvee E , Cerra MC , Wong WP , Tota B , Ip YK . The structural characteristics of the heart ventricle of the African lungfish Protopterus dolloi: Freshwater and aestivation. J Anat 213: 106‐119, 2008.
 281. Ideker T , Thorsson V , Ranish JA , Christmas R , Buhler J , Eng JK , Bumgarner R , Goodlett DR , Aebersold R , Hood L . Integrated genomic and proteomic analyses of a systematically perturbed metabolic network. Science 292: 929‐934, 2001.
 282. Idler DR , Ronald AP , Schmidt PJ . Biochemical studies on sockeye salmon during spawning migration: VII. Steroid hormones in plasma. Can J Biochem Physiol 37: 1227‐1238, 1959.
 283. Ivacic DL , Labisky RF . Metabolic responses of mourning doves to short term food and temperature stresses in winter. Wilson Bull 85: 182‐196, 1973.
 284. Iwakiri R , Gotoh Y , Noda T , Sugihara H , Fujimoto K , Fuseler J , Aw TY . Programmed cell death in rat intestine: Effect of feeding and fasting. Scand J Gastroenterol 36: 39‐47, 2001.
 285. Jackson K , Kley NJ , Brainerd EL . How snakes eat snakes: The biomechanical challenges of ophiophagy for the California kingsnake, Lampropeltis getula californiae (Serpentes : Colubridae). Zoology 107: 191‐200, 2004.
 286. James MC , Eckert SA , Myers RA . Migratory and reproductive movements of male leatherback turtles (Dermochelys coriacea). Mar Biol 147: 845‐853, 2005.
 287. James RS . Effects of aestivation on skeletal muscle performance. Prog Mol Subcell Biol 49: 171‐181, 2010.
 288. James RS , Staples JF , Brown JC , Tessier SN , Storey KB . The effects of hibernation on the contractile and biochemical properties of skeletal muscles in the thirteen‐lined ground squirrel, Ictidomys tridecemlineatus . J Exp Biol 216: 2587‐2594, 2013.
 289. Janes DN , Chappell MA . The effect of ration size and body size on specific dynamic action in Adelie penguin chicks, Pygoscelis adeliae . Physiol Zool 68: 1029‐1044, 1995.
 290. Jani A , Orlicky DJ , Karimpour‐Fard A , Epperson LE , Russell RL , Hunter LE , Martin SL . Kidney proteome changes provide evidence for a dynamic metabolism and regional redistribution of plasma proteins during torpor‐arousal cycles of hibernation. Physiol Genomics 44: 717‐727, 2012.
 291. Janssens PA . The metabolism of the aestivating African lungfish. Comp Biochem Physiol 11: 105‐117, 1964.
 292. Janssens PA , Cohen PP . Biosynthesis of urea in the estivating African lungfish and in Xenopus laevis under conditions of water‐shortage. Comp Biochem Physiol 24: 887‐898, 1968.
 293. Jeffrey DA , Peakall DB , Miller DS , Herzberg GR . Blood chemistry changes in food‐deprived herring gulls. Comp Biochem Physiol A 81: 911‐913, 1985.
 294. Johnson LR , McCormack SA . Regulation of gastrointestinal mucosal growth. In: Johnson LR, editor. Physiology of the Gastrointestinal Tract. New York: Raven Press, 1994, pp. 611‐641.
 295. Johnson OW , Morton ML , Bruner PL , Johnson PM . Fat cyclicity, predicted migratory flight ranges, and features of wintering behavior in pacific golden‐plovers. Condor 91: 156‐177, 1989.
 296. Johnson SR , West GC . Fat content, fatty acid composition and estimates of energy metabolism of adelie penguins (Pygoscelis adeliae) during the early breeding season fast. Comp Biochem Physiol B 45: 709‐719, 1973.
 297. Johnston IA . Quantitative analysis of muscle breakdown during starvation in the marine flatfish Pleuronectes platessa . Cell Tissue Res 214: 369‐386, 1981.
 298. Johnston IA , Moon TW . Glycolytic and gluconeogenic enzyme activities in the skeletal muscles and liver of a teleost fish (Pleuronectes platessa). Biochem Soc Trans 7: 661‐663, 1979.
 299. Jordan JS . Effects of starvation on wild mallards. J Wildlife Manage 17: 304‐311, 1953.
 300. Kaetzel CS . Cooperativity among secretory IgA, the polymeric immunoglobulin receptor, and the gut microbiota promotes host‐microbial mutualism. Immunol Lett 162: 10‐21, 2014.
 301. Karasov WH . Daily energy‐expenditure and the cost of activity in mammals. Am Zool 32: 238‐248, 1992.
 302. Karasov WH , Pinshow B , Starck JM , Afik D . Anatomical and histological changes in the alimentary tract of migrating blackcaps (Sylvia atricapilla): A comparison among fed, fasted, food‐restricted, and refed birds. Physiol Biochem Zool 77: 149‐160, 2004.
 303. Kendleigh C . Resistance to hunger in birds. J Wildlife Manage 9: 217‐226, 1945.
 304. Kennett R , Christian K . Metabolic depression in estivating long‐neck turtles (Chelodina rugosa). Physiol Zool 67: 1087‐1102, 1994.
 305. King JR , Murphy ME . Periods of nutritional stress in the annual cycles of endotherms ‐ fact or fiction. Am Zool 25: 955‐964, 1985.
 306. Knepton J . A note on the burrowing habits of the salamander Amphiuma means means . Copeia 1954: 68, 1954.
 307. Knight JE , Narus EN , Martin SL , Jacobson A , Barnes BM , Boyer BB . mRNA stability and polysome loss in hibernating Arctic ground squirrels (Spermophilus parryii). Mol Cell Biol 20: 6374‐6379, 2000.
 308. Kohl KD , Amaya J , Passement CA , Dearing MD , McCue MD . Unique and shared responses of the gut microbiota to prolonged fasting: A comparative study across five classes of vertebrate hosts. FEMS Microbiol Ecol 90: 883‐894, 2015.
 309. Korschgen CE . Breeding stress of female eiders in Maine. J Wildlife Manage 41: 360‐373, 1977.
 310. Krilowicz BL . Ketone body metabolism in a ground squirrel during hibernation and fasting. Am J Physiol Regul Integr Comp Physiol 249: R462‐R470, 1985.
 311. Krogdahl A , Bakke‐McKellep AM . Fasting and refeeding cause rapid changes in intestinal tissue mass and digestive enzyme capacities of Atlantic salmon (Salmo salar L.). Comp Biochem Physiol A 141: 450‐460, 2005.
 312. Kunz TH , Wrazen JA , Burnett CD . Changes in body mass and fat reserves in pre‐hibernating little brown bats (Myotis lucifugus). Ecoscience 5: 8‐17, 1998.
 313. Kurtz CC , Carey HV . Seasonal changes in the intestinal immune system of hibernating ground squirrels. Dev Comp Immunol 31: 415‐428, 2007.
 314. Langer S , Sharma J , Sharma S . Effect of starvation on the cortisol levels of fish Garra gotyla gotyla . Int J Adv Biol Res 4: 24‐26, 2014.
 315. Laplaud PM , Saboureau M , Beaubatie L , el‐Omari B . Seasonal variations of plasma lipids and lipoproteins in the hedgehog, an animal model for lipoprotein (a) metabolism: Relation to plasma thyroxine and testosterone levels. Biochim Biophys Acta 1005: 143‐156, 1989.
 316. Larsen DA , Beckman BR , Dickhoff WW . The effect of low temperature and fasting during the winter on growth and smoltification of coho salmon. N Am J Aquacult 63: 1‐10, 2001.
 317. Larsen DA , Beckman BR , Dickhoff WW . The effect of low temperature and fasting during the winter on metabolic stores and endocrine physiology (insulin, insulin‐like growth factor‐I and thyroxine) of coho salmon, Oncorhynchus kisutch . Gen Comp Endocrinol 123: 308‐323, 2001.
 318. Larsson A , Lewander K . Metabolic effects of starvation in eel, Anguilla anguilla L . Comp Biochem Physiol A 44: 367‐374, 1973.
 319. Laske TG , Harlow HJ , Garshelis DL , Iaizzo PA . Extreme respiratory sinus arrhythmia enables overwintering black bear survival–physiological insights and applications to human medicine. J Cardiovas Translat Res 3: 559‐569, 2010.
 320.Le Boeuf B , Laws RM . Elephant Seals: Population Ecology, Behavior, and Physiology. Berkeley: University of California Press, 1994.
 321.Le Maho Y , Cherel C , Robin J‐P . Starvation as a treatment for obesity: The need to conserve body protein. NIPS 3: 21‐24, 1988.
 322. Le Maho Y , Vankha HV , Koubi H , Dewasmes G , Girard J , Ferre P , Cagnard M . Body composition, energy expenditure, and plasma metabolites in long term fasting geese. Am J Physiol Endocrinol Metab 241: E342‐E354, 1981.
 323. LeBlanc PJ , Obbard M , Battersby BJ , Felskie AK , Brown L , Wright PA , Ballantyne JS . Correlations of plasma lipid metabolites with hibernation and lactation in wild black bears Ursus americanus . J Comp Physiol B 171: 327‐334, 2001.
 324. Lee AK , Mercer EH . Cocoon surrounding desert‐dwelling frogs. Science 157: 87‐88, 1967.
 325. Lee K , So H , Gwag T , Ju H , Lee JW , Yamashita M , Choi I . Molecular mechanism underlying muscle mass retention in hibernating bats: Role of periodic arousal. J Cell Physiol 222: 313‐319, 2010.
 326. Leech AR , Goldstein L , Cha CJ , Goldstein JM . Alanine biosynthesis during starvation in skeletal muscle of the spiny dogfish, Squalus acanthias . J Exp Zool 207: 73‐80, 1979.
 327. Lignot JH . Changes in form and function of the gastrointestinal tract during starvation: From pythons to rats. In: McCue MD , editor. Comparative Physiology of Fasting, Starvation, and Food Limitation. Berlin: Springer‐Verlag, 2012, pp. 309‐336.
 328. Lignot JH , Helmstetter C , Secor SM . Postprandial morphological response of the intestinal epithelium of the Burmese python (Python molurus). Comp Biochem Physiol A 141: 280‐291, 2005.
 329. Lim ALL , Ip YK . Effect of Fasting on glycogen metabolism and activities of glycolytic and gluconeogenic enzymes in the mudskipper Boleophthalmus boddaerti . J Fish Biol 34: 349‐367, 1989.
 330. Lindstedt SL . Energetics and water economy of the smallest desert mammal. Physiol Zool 53: 82‐97, 1980.
 331. Lohuis TD , Harlow HJ , Beck TD , Iaizzo PA . Hibernating bears conserve muscle strength and maintain fatigue resistance. Physiol Biochem Zool 80: 257‐269, 2007.
 332. Lomholt J. Breathing in the Aestivating African Lungfish, Protopterus Amphibious. New Delhi: Narenda, 1993.
 333. Long JD , Orlando RC . Esophageal submucosal glands: Structure and function. The Am J Gastroenterol 94: 2818‐2824, 1999.
 334. Loong AM , Hiong KC , Wong WP , Chew SF , Ip YK . Differential gene expression in the liver of the African lungfish, Protopterus annectens, after 6 days of estivation in air. J Comp Physiol B 182: 231‐245, 2012.
 335. Loong AM , Pang CY , Hiong KC , Wong WP , Chew SF , Ip YK . Increased urea synthesis and/or suppressed ammonia production in the African lungfish, Protopterus annectens, during aestivation in air or mud. J Comp Physiol B 178: 351‐363, 2008.
 336. Love RM . Studies on the north sea cod. III. Effects of starvation. J Sci Food Agric 9: 617‐620, 1958.
 337. Loveridge JP , Withers PC . Metabolism and water‐balance of active and cocooned African bullfrogs Pyxicephalus adspersus . Physiol Zool 54: 203‐214, 1981.
 338. Lowery MS , Roberts SJ , Somero GN . Effects of starvation on the activities and localization of glycolytic‐enzymes in the white muscle of the barred sand bass Paralabrax nebulifer . Physiol Zool 60: 538‐549, 1987.
 339. Lundberg DA , Nelson RA , Wahner HW , Jones JD . Protein metabolism in the black bear before and during hibernation. Mayo Clin Proc 51: 716‐722, 1976.
 340. Luppa H. Histology of the Digestive Tract. New York: Academic Press, 1977.
 341. Lydersen C , Kovacs KM , Hammill MO . Energetics during nursing and early postweaning fasting in hooded seal (Cystophora cristata) pups from the Gulf of St Lawrence, Canada. J Comp Physiol B 167: 81‐88, 1997.
 342. Lyman CP , Willis JS , Malan A , Wang LCH . Hibernation and Torpor in Mammals and Birds. New York: Academic Press, 1982.
 343. Machado CR , Garofalo MA , Roselino JE , Kettelhut IC , Migliorini RH . Effects of starvation, refeeding, and insulin on energy‐linked metabolic processes in catfish (Rhamdia hilarii) adapted to a carbohydrate‐rich diet. Gen Comp Endocrinol 71: 429‐437, 1988.
 344. Maddock DM , Burton MPM . Some effects of starvation on the lipid and skeletal‐muscle layers of the winter flounder, Pleuronectes americanus . Can J Zool 72: 1672‐1679, 1994.
 345. Magnus TH , Henderson NE . Thyroid hormone resistance in hibernating ground squirrels, Spermophilus richardsoni. I. Increased binding of triiodo‐L‐thyronine and L‐thyroxine by serum proteins. Gen Comp Endocrinol 69: 352‐360, 1988.
 346. Magnus TH , Henderson NE . Thyroid hormone resistance in hibernating ground squirrels, Spermophilus richardsoni. II. Reduction of hepatic nuclear receptors. Gen Comp Endocrinol 69: 361‐371, 1988.
 347. Main AR , Bentley PJ . Water relations of Australian burrowing frogs and tree frogs. Ecology 45: 379‐382, 1964.
 348. Mantle BL , Hudson NJ , Harper GS , Cramp RL , Franklin CE . Skeletal muscle atrophy occurs slowly and selectively during prolonged aestivation in Cyclorana alboguttata (Gunther 1867). J Exp Biol 212: 3664‐3672, 2009.
 349. Marks JS , Redmond RL . Migration of bristle‐thighed curlews on Laysan Island ‐ timing, behavior and estimated flight range. Condor 96: 316‐330, 1994.
 350. Martin S , Epperson LE , van Breukelen F , Heldmaier G , Klingenspor M . Quantitative and qualitative changes in gene expression during hibernation in golden‐mantled ground squirrels. In: Heldmaier H, Klingenspor M, editors. Life in the Cold. Berlin: Springer‐Verlag, 2000, pp. 315‐324.
 351. Martin SL , Epperson LE , Rose JC , Kurtz CC , Ane C , Carey HV . Proteomic analysis of the winter‐protected phenotype of hibernating ground squirrel intestine. Am J Physiol Regul Integr Comp Physiol 295: R316‐R328, 2008.
 352. Martinez B , Sonanez‐Organis JG , Vazquez‐Medina JP , Viscarra JA , MacKenzie DS , Crocker DE , Ortiz RM . Prolonged food deprivation increases mRNA expression of deiodinase 1 and 2, and thyroid hormone receptor beta‐1 in a fasting‐adapted mammal. J Exp Biol 216: 4647‐4654, 2013.
 353. Martof BS . Prolonged inanition in Siren lacertina. Copeia 1969: 285‐289, 1969.
 354. Mayer VW , Bernick S . Comparative histological studies of the stomach, small intestine, and colon of warm and active and hibernating arctic ground squirrels, Spermophilus undulatus . Anat Rec 130: 747‐757, 1958.
 355. McBride JR , Fagerlund UHM , Dye HM , Bagshaw J . Changes in structure of tissues and in plasma‐cortisol during the spawning migration of pink salmon, Oncorhynchus‐gorbuscha (Walbaum). J Fish Biol 29: 153‐166, 1986.
 356. McClanahan L . Adaptations of spadefoot toad Scaphiopus couchi to desert environments. Comp Biochem Physiol 20: 73‐99, 1967.
 357. McClanahan L . Changes in body‐fluids of burrowed spadefoot toads as a function of soil‐water potential. Copeia 1972: 209‐216, 1972.
 358. McClanahan LL , Shoemaker VH , Ruibal R . Structure and function of cocoon of a ceratophryd Frog. Copeia 1976: 179‐185, 1976.
 359. McCue MD . Snakes survive starvation by employing supply‐ and demand‐side economic strategies. Zoology (Jena) 110: 318‐327, 2007.
 360. McCue MD . Western diamondback rattlesnakes demonstrate physiological and biochemical strategies for tolerating prolonged starvation. Physiol Biochem Zool 80: 25‐34, 2007.
 361. McCue MD . Starvation physiology: Reviewing the different strategies animals use to survive a common challenge. Comp Biochem Physiol A 156: 1‐18, 2010.
 362. McCue MD , Amaya JA , Yang AS , Erhardt EB , Wolf BO , Hanson DT . Targeted 13C enrichment of lipid and protein pools in the body reveals circadian changes in oxidative fuel mixture during prolonged fasting: A case study using Japanese quail. Comp Biochem Physiol A 166: 546‐554, 2013.
 363. McFall‐Ngai M , Hadfield MG , Bosch TC , Carey HV , Domazet‐Loso T , Douglas AE , Dubilier N , Eberl G , Fukami T , Gilbert SF , Hentschel U , King N , Kjelleberg S , Knoll AH , Kremer N , Mazmanian SK , Metcalf JL , Nealson K , Pierce NE , Rawls JF , Reid A , Ruby EG , Rumpho M , Sanders JG , Tautz D , Wernegreen JJ . Animals in a bacterial world, a new imperative for the life sciences. Proc Natl Acad Sci U S A 110: 3229‐3236, 2013.
 364. McGee‐Lawrence ME , Stoll DM , Mantila ER , Fahrner BK , Carey HV , Donahue SW . Thirteen‐lined ground squirrels (Ictidomys tridecemlineatus) show microstructural bone loss during hibernation but preserve bone macrostructural geometry and strength. J Exp Biol 214: 1240‐1247, 2011.
 365. McGee‐Lawrence ME , Wojda SJ , Barlow LN , Drummer TD , Bunnell K , Auger J , Black HL , Donahue SW . Six months of disuse during hibernation does not increase intracortical porosity or decrease cortical bone geometry, strength, or mineralization in black bear (Ursus americanus) femurs. J Biomech 42: 1378‐1383, 2009.
 366. McGee‐Lawrence ME , Wojda SJ , Barlow LN , Drummer TD , Castillo AB , Kennedy O , Condon KW , Auger J , Black HL , Nelson OL , Robbins CT , Donahue SW . Grizzly bears (Ursus arctos horribilis) and black bears (Ursus americanus) prevent trabecular bone loss during disuse (hibernation). Bone 45: 1186‐1191, 2009.
 367. Mckay ME . The digestive system of the eel pout (Zoarces anguillaris). Biol Bull 56: 8‐23, 1929.
 368. McLean IG , Towns AJ . Differences in weight changes and the annual cycle of male and female arctic ground squirrels. Arctic 34: 249‐254, 1981.
 369. Mcleese JM , Moon TW . Seasonal changes in the intestinal mucosa of winter flounder, Pseudopleuronectes americanus (Walbaum), from Passamaquoddy Bay, New‐Brunswick. J Fish Biol 35: 381‐393, 1989.
 370. McMullen DC , Hallenbeck JM . Regulation of Akt during torpor in the hibernating ground squirrel, Ictidomys tridecemlineatus . J Comp Physiol B 180: 927‐934, 2010.
 371. Mech L. The Wolf: The Ecology and Behavior of an Endangered Species. New York: Natural History Press, 1970.
 372. Mellish JE , Iverson SJ . Blood metabolites as indicators of nutrient utilization in fasting, lactating phocid seals: Does depletion of nutrient reserves terminate lactation? Can J Zool 79: 303‐311, 2001.
 373. Mendez G , Wieser W . Metabolic responses to food deprivation and refeeding in juveniles of Rutilus rutilus (Teleostei, Cyprinidae). Envir Biol Fish 36: 73‐81, 1993.
 374. Merkle S , Hanke W . Long term starvation in Xenopus laevis Daudin‐I. Effects on general metabolism. Comp Biochem Physiol B 89: 719‐730, 1988.
 375. Merkle S , Hanke W . Long term starvation in Xenopus laevis Daudin‐II. Effects on several organs. Comp Biochem Physiol A 90: 491‐495, 1988.
 376. Misch DW , Giebel PE , Faust RE . Intestinal microvilli: Responses to feeding and fasting. Eur J Cell Biol 21: 269‐279, 1980.
 377. Mommsen TP , French CJ , Hochachka PW . Sites and patterns of protein and amino acid utilization during the spawning migration of salmon. Can J Zool 58: 1785‐1799, 1980.
 378. Mommsen TP , Moon TW . Metabolic actions of glucagon‐family hormones in liver. Fish Physiol Biochem 7: 279‐288, 1989.
 379. Montgomery WL , Pollak PE . Gut anatomy and pH in a Red Sea surgeonfish, Acanthurus nigrofuscus . Mar Ecol Prog Ser 44: 7‐13, 1988.
 380. Moon TW , Foster GD , Plisetskaya EM . Changes in peptide hormones and liver enzymes in the rainbow trout deprived of food for 6 weeks. Can J Zool 67: 2189‐2193, 1989.
 381. Moon TW , Johnston IA . Starvation and enzyme activities in the skeletal muscles and liver of a teleost fish (Pleuronectes platessa). Biochem Soc Trans 7: 1045‐1046, 1979.
 382. Morton GJ , Meek TH , Schwartz MW . Neurobiology of food intake in health and disease. Nat Rev Neurosci 15: 367‐378, 2014.
 383. Mosin AF . Some physiological and biochemical features of starvation and refeeding in small wild rodents (Microtinae). Comp Biochem Physiol A 71: 461‐464, 1982.
 384. Moyes CD , Schulte PM . Principles of Animal Physiology. San Francisco: Benjamin Cummings, 2006.
 385. Mrosovsky N . Lipid programs and life strategies in hibernators. Am Zool 16: 685‐697, 1976.
 386. Mrosovsky N , Sherry DF . Animal anorexias. Science 207: 837‐842, 1980.
 387. Muegge BD , Kuczynski J , Knights D , Clemente JC , Gonzalez A , Fontana L , Henrissat B , Knight R , Gordon JI . Diet drives convergence in gut microbiome functions across mammalian phylogeny and within humans. Science 332: 970‐974, 2011.
 388. Muir TJ , Costanzo JP , Lee RE, Jr . Metabolic depression induced by urea in organs of the wood frog, Rana sylvatica: Effects of season and temperature. J Exp Zool A 309: 111‐116, 2008.
 389. Mustonen AM , Kakela R , Asikainen J , Nieminen P . Selective fatty acid mobilization from adipose tissues of the pheasant (Phasianus colchicus mongolicus) during food deprivation. Physiol Biochem Zool 82: 531‐540, 2009.
 390. Mustonen AM , Kakela R , Kakela A , Pyykonen T , Aho J , Nieminen P . Lipid metabolism in the adipose tissues of a carnivore, the raccoon dog, during prolonged fasting. Exp Biol Med 232: 58‐69, 2007.
 391. Mustonen AM , Nieminen P , Puukka M , Asikainen J , Saarela S , Karonen SL , Kukkonen JV , Hyvarinen H . Physiological adaptations of the raccoon dog (Nyctereutes procyonoides) to seasonal fasting‐fat and nitrogen metabolism and influence of continuous melatonin treatment. J Comp Physiol B 174: 1‐12, 2004.
 392. Mustonen AM , Puukka M , Pyykonen T , Nieminen P . Adaptations to fasting in the American mink (Mustela vison): Nitrogen metabolism. J Comp Physiol B 175: 357‐363, 2005.
 393. Mustonen AM , Puukka M , Saarela S , Paakkonen T , Aho J , Nieminen P . Adaptations to fasting in a terrestrial mustelid, the sable (Martes zibellina). Comp Biochem Physiol A 144: 444‐450, 2006.
 394. Mustonen AM , Saarela S , Nieminen P . Food deprivation in the common vole (Microtus arvalis) and the tundra vole (Microtus oeconomus). J Comp Physiol B 178: 199‐208, 2008.
 395. Mutel E , Gautier‐Stein A , Abdul‐Wahed A , Amigo‐Correig M , Zitoun C , Stefanutti A , Houberdon I , Tourette JA , Mithieux G , Rajas F . Control of blood glucose in the absence of hepatic glucose production during prolonged fasting in mice: Induction of renal and intestinal gluconeogenesis by glucagon. Diabetes 60: 3121‐3131, 2011.
 396. Nagel A . Torpor in the European white‐toothed shrews. Experientia 33: 1455‐1456, 1977.
 397. Navarro I , Gutierrez J . Fasting and starvation. In: Hochachka PW , Mommsen TP , editors. Biochemistry and Molecular Biology of Fishes, Metabolic Biochemistry. Amsterdam: Elsevier, 1995, pp. 393–434.
 398. Navarro I , Gutierrez J , Planas J . Changes in plasma glucagon, insulin and tissue metabolites associated with prolonged fasting in brown trout (Salmo trutta fario) during two different seasons of the year. Comp Biochem Physiol A 102: 401‐407, 1992.
 399. Naya DE , Veloso C , Sabat P , Bozinovic F . The effect of short‐ and long‐term fasting on digestive and metabolic flexibility in the Andean toad, Bufo spinulosus . J Exp Biol 212: 2167‐2175, 2009.
 400. Nedvidkova J , Smitka K , Kopsky V , Hainer V . Adiponectin, an adipocyte‐derived protein. Physiol Res 54: 133‐140, 2005.
 401. Nelson CJ , Otis JP , Carey HV . Global analysis of circulating metabolites in hibernating ground squirrels. Comp Biochem Physiol D 5: 265‐273, 2010.
 402. Nelson OL , Robbins CT , Wu Y , Granzier H . Titin isoform switching is a major cardiac adaptive response in hibernating grizzly bears. Am J Physiol Heart Circ Physiol 295: H366‐H371, 2008.
 403. Nelson RA . Protein and fat metabolism in hibernating bears. Fed Proc 39: 2955‐2958, 1980.
 404. Nelson RA . Black bears and polar bears–still metabolic marvels. Mayo Clin Proc 62: 850‐853, 1987.
 405. Nelson RA . Nitrogen conservation and its turnover in hibernation. In: Malan A , Canguilhem B , editors. Living in the Cold. London: Libbey Eurotext, 1989, pp. 299‐307.
 406. Neubert E , Scholze C , Kratzsch J , Gurtler H . Plasma levels of catecholamines and lipolysis during starvation in growing pigs. J. Veterinary Med Series A 46: 247‐253, 1999.
 407. Newsholme EA , Leech AR . Biochemistry for the Medical Sciences. New York: Wiley, 1983.
 408. Nieminen P , Rouvinen‐Watt K , Saarela S , Mustonen AM . Fasting in the American marten (Martes americana): A physiological model of the adaptations of a lean‐bodied animal. J Comp Physiol B 177: 787‐795, 2007.
 409. Norberg L , Mardh S . A continuous‐flow technique for analysis of stoichiometry and transport kinetics of gastric H, K‐ATPase. Acta Physiol Scand 140: 567‐573, 1990.
 410. Nordoy ES , Aakvaag A , Larsen TS . Metabolic adaptations to fasting in harp seal pups. Physiol Zool 66: 926‐945, 1993.
 411. Nordoy ES , Blix AS . Energy sources in fasting grey seal pups evaluated with computed tomography. Am J Physiol Regul Integr Comp Physiol 249: R471‐R476, 1985.
 412. Nordoy ES , Stijfhoorn DE , Raheim A , Blix AS . Water flux and early signs of entrance into phase III of fasting in grey seal pups. Acta Physiol Scand 144: 477‐482, 1992.
 413. Nowell MM , Choi H , Rourke BC . Muscle plasticity in hibernating ground squirrels (Spermophilus lateralis) is induced by seasonal, but not low‐temperature, mechanisms. J Comp Physiol B 181: 147‐164, 2011.
 414. O'Hara BF , Watson FL , Srere HK , Kumar H , Wiler SW , Welch SK , Bitting L , Heller HC , Kilduff TS . Gene expression in the brain across the hibernation cycle. J Neurosci 19: 3781‐3790, 1999.
 415. Oftedal OT , Bowen WD , Widdowson EM , Boness DJ . Effects of suckling and the postsuckling fast on weights of the body and internal organs of harp and hooded seal pups. Biol Neonate 56: 283‐300, 1989.
 416. Okada T , Fukuda S , Hase K , Nishiumi S , Izumi Y , Yoshida M , Hagiwara T , Kawashima R , Yamazaki M , Oshio T , Otsubo T , Inagaki‐Ohara K , Kakimoto K , Higuchi K , Kawamura YI , Ohno H , Dohi T . Microbiota‐derived lactate accelerates colon epithelial cell turnover in starvation‐refed mice. Nat Commun 4: 1654, 2013.
 417. Okumura JI , Tasaki I . Effect of fasting, refeeding and dietary protein level on uric acid and ammonia content of blood, liver and kidney in chickens. J Nutr 97: 316‐320, 1969.
 418. Oppenheimer JR . Mouthbreeding in fishes. Anim Behav 18: 493‐503, 1970.
 419. Ortiz CL , Costa D , Leboeuf BJ . Water and energy flux in elephant seal pups fasting under natural conditions. Physiol Zool 51: 166‐178, 1978.
 420. Ortiz RM , Wade CE , Ortiz CL . Effects of prolonged fasting on plasma cortisol and TH in postweaned northern elephant seal pups. Am J Physiol Regul Integr Comp Physiol 280: R790‐R795, 2001.
 421. Otis JP , Sahoo D , Drover VA , Yen CL , Carey HV . Cholesterol and lipoprotein dynamics in a hibernating mammal. PLoS One 6: e29111, 2011.
 422. Ott BD , Secor SM . Adaptive regulation of digestive performance in the genus Python. J Exp Biol 210: 340‐356, 2007.
 423. Owen OE , Felig P , Morgan AP , Wahren J , Cahill GF, Jr . Liver and kidney metabolism during prolonged starvation. J Clin Invest 48: 574‐583, 1969.
 424. Papastamatiou YP , Lowe CG . Postprandial response of gastric pH in leopard sharks (Triakis semifasciata) and its use to study foraging ecology. J Exp Biol 207: 225‐232, 2004.
 425. Papastamatiou YP , Purkis SJ , Holland KN . The response of gastric pH and motility to fasting and feeding in free swimming blacktip reef sharks, Carcharhinus melanopterus . J Exp Mar Biol Ecol 345: 129‐140, 2007.
 426. Parilla R . Flux of metabolic fuels during starvation in the rat. Pflügers Arch 374: 3‐7, 1978.
 427. Park KG , Park KS , Kim MJ , Kim HS , Suh YS , Ahn JD , Park KK , Chang YC , Lee IK . Relationship between serum adiponectin and leptin concentrations and body fat distribution. Diabetes Res Clin Pr 63: 135‐142, 2004.
 428. Patterson S , Goldspink G . The effect of starvation on the ultrastructure of the red and white myotomal muscles of the crucian carp (Carassius carassius). Z Zellforsch Mikrosk Anat 146: 375‐384, 1973.
 429. Peckett AJ , Wright DC , Riddell MC . The effects of glucocorticoids on adipose tissue lipid metabolism. Metabolism 60: 1500‐1510, 2011.
 430. Pernia SD , Hill A , Ortiz CL . Urea turnover during prolonged fasting in the northern elephant seal. Comp Biochem Physiol B 65: 731‐734, 1980.
 431. Peterson CC , Stone PA . Physiological capacity for estivation of the sonoran mud turtle, Kinosternon sonoriense . Copeia 2000: 684‐700, 2000.
 432. Petranka J. Salamanders of the United States and Canada. Washington D. C., USA: Smithsonian Institution, 1998.
 433. Pfeiffer EW , Reinking LN , Hamilton JD . Some effects of food and water deprivation on metabolism in black‐tailed prairie dogs, Cynomys ludovicianus . Comp Biochem Physiol A 63: 19‐22, 1979.
 434. Phillips JA . Movement patterns and density of Varanus albigularis . J Herpetol 29: 407‐416, 1995.
 435. Pinder A , Storey K , Ultsch G . Estivation and hibernation. In: Feder ME , Burggren WW , editors. Environmental Physiology of the Amphibians. Chicago: University of Chicago Press, 1992, pp. 250‐276.
 436. Pinheiro EC , Taddei VA , Migliorini RH , Kettelhut IC . Effect of fasting on carbohydrate metabolism in frugivorous bats (Artibeus lituratus and Artibeus jamaicensis). Comp Biochem Physiol B 143: 279‐284, 2006.
 437. Plisetskaya EM . Glucagon and related peptides (an overview). Prog Clin Bioll Res 342: 67‐72, 1990.
 438. Pond CM. The Fats of Life. Cambridge: Cambridge University Press, 1998.
 439. Poulson T. Animals in Aquatic Environments: Animals in Caves. Washington: American Physiological Society, 1964.
 440. Price ER , Jones TT , Wallace BP , Guglielmo CG . Serum triglycerides and beta‐hydroxybutyrate predict feeding status in green turtles (Chelortia mydas): Evaluating a single blood sample method for assessing feeding/fasting in reptiles. J Exp Mar Biol Ecol 439: 176‐180, 2013.
 441. Prince PA , Ricketts C , Thomas G . Weight loss in incubating albatrosses and its implications for their energy and food requirements. Condor 83: 238‐242, 1981.
 442. Rapatz GL , Musacchia XJ . Metabolism of Chrysemys picta during fasting and during cold torpor. Am J Physiol 188: 456‐460, 1957.
 443. Rauch JS , Behrisch HW . Ketone bodies: A source of energy during hibernation. Can J Zool 59: 754‐760, 1981.
 444. Rea LD , Rosen DAS , Trites AW . Metabolic response to fasting in 6‐week‐old Steller sea lion pups (Eumetopias jubatus). Can J Zool 78: 890‐894, 2000.
 445. Reenstra WW , Forte JG . H+/ATP stoichiometry for the gastric (K+/H+)‐ATPase. J Membr Biol 61: 55‐60, 1981.
 446. Reilly BD , Schlipalius DI , Cramp RL , Ebert PR , Franklin CE . Frogs and estivation: Transcriptional insights into metabolism and cell survival in a natural model of extended muscle disuse. Physiol Genomics 45: 377‐388, 2013.
 447. Reilly JJ . Adaptations to prolonged fasting in free‐living weaned gray seal pups. Am J Physiol Regul Integr Comp Physiol 260: R267‐R272, 1991.
 448. Reinmuth OM , Scheinberg P , Bourne B . Total cerebral blood flow and metabolism. Arch Neurol 12: 49‐66, 1964.
 449. Reiter J , Stinson NL , Leboeuf BJ . Northern elephant seal development ‐ transition from weaning to nutritional independence. Behav Ecol Sociobiol 3: 337‐367, 1978.
 450. Reno HW , Gehlbach FR , Turner RA . Skin and aestivational cocoon of aquatic amphibian Siren intermedia Le Conte. Copeia 1972: 625‐631, 1972.
 451. Rescan PY , Montfort J , Ralliere C , Le Cam A , Esquerre D , Hugot K . Dynamic gene expression in fish muscle during recovery growth induced by a fasting‐refeeding schedule. BMC Genomics 8: 438, 2007.
 452. Rice DW , Wolman AA , Braham HW . The gray whale, Eschrichtius robustus . Mar Fish Rev 46: 7‐14, 1984.
 453. Richards JG . Metabolic rate suppression as a mechanism for surviving environmental challenge in fish. Prog Mol Subcell Biol 49: 113‐139, 2010.
 454. Riddle WA . Physiological ecology of land snails and slugs. In: Russell‐Hunter WD , editor. The Mollusca. New York: Academic Press, 1983, pp. 431‐461.
 455. Rider MH . Role of AMP‐activated protein kinase in metabolic depression in animals. J Comp Physiol B (in press), 2015 [Epub ahead of print].
 456. Riedesel ML , Steffen JM . Protein metabolism and urea recycling in rodent hibernators. Fed Proc 39: 2959‐2963, 1980.
 457. Rios FS , Kalinin AL , Fernandes MN , Rantin FT . Changes in gut gross morphology of traira, Hoplias malabaricus (Teleostei, Erythrinidae) during long‐term starvation and after refeeding. Brazilian J Biol 64: 683‐689, 2004.
 458. Rios FS , Kalinin AL , Rantin FT . The effects of long‐term food deprivation on respiration and haematology of the neotropical fish Hoplias malabaricus . J Fish Biol 61: 85‐95, 2002.
 459. Riquelme CA , Magida JA , Harrison BC , Wall CE , Marr TG , Secor SM , Leinwand LA . Fatty acids identified in the Burmese python promote beneficial cardiac growth. Science 334: 528‐531, 2011.
 460. Robin JP , Cherel Y , Girard H , Chaban C , Le Maho Y . Augmentation of nitrogen efficiency and hyperphagia associated with refeeding after prolonged fast in the domestic goose. C R Acad Sci III 306: 375‐379, 1988.
 461. Robin JP , Cherel Y , Girard H , Geloen A , Le Maho Y . Uric acid and urea in relation to protein catabolism in long‐term fasting geese. J Comp Physiol B 157: 491‐499, 1987.
 462. Robin JP , Fayolle C , Decrock F , Thil MA , Cote SD , Bernard S , Groscolas R . Restoration of body mass in king penguins after egg abandonment at a critical energy depletion stage: Early vs late breeders. J Avian Biol 32: 303‐310, 2001.
 463. Robin JP , Frain M , Sardet C , Groscolas R , Le Maho Y . Protein and lipid utilization during long‐term fasting in emperor penguins. Am J Physiol Regul Integr Comp Physiol 254: R61‐R68, 1988.
 464. Robinson AM , Williamson DH . Physiological roles of ketone bodies as substrates and signals in mammalian tissues. Physiol Rev 60: 143‐187, 1980.
 465. Rodriguez P , Tortosa FS , Villafuerte R . The effects of fasting and refeeding on biochemical parameters in the red‐legged partridge (Alectoris rufa). Comp Biochem Physiol A 140: 157‐164, 2005.
 466. Roe J , Georges A . Maintenance of variable responses for coping with wetland drying in freshwater turtles. Ecology 89: 485‐494, 2008.
 467. Roitt I , Brostoff J , Male D . Immunology. Edinburgh: Mosby, 2001.
 468. Romero LM , Wikelski M . Corticosterone levels predict survival probabilities of Galapagos marine iguanas during El Nino events. Proc Natl Acad Sci U S A 98: 7366‐7370, 2001.
 469. Rose F . Turtles in arid and semi‐arid regions. Bull Ecol Soc Am 61: 89, 1980.
 470. Rose JC , Epperson LE , Carey HV , Martin SL . Seasonal liver protein differences in a hibernator revealed by quantitative proteomics using whole animal isotopic labeling. Comp Biochem Physiol D 6: 163‐170, 2011.
 471. Roselis S , Da Silva M , Miglorini R . Effects of starvation and refeeding on energy‐linked metabolic processes in the turtle (Phrynops hilarii). Comp Biochem Physiol A 96: 415‐419, 1990.
 472. Rourke BC , Cotton CJ , Harlow HJ , Caiozzo VJ . Maintenance of slow type I myosin protein and mRNA expression in overwintering prairie dogs (Cynomys leucurus and ludovicianus) and black bears (Ursus americanus). J Comp Physiol B 176: 709‐720, 2006.
 473. Rourke BC , Yokoyama Y , Milsom WK , Caiozzo VJ . Myosin isoform expression and MAFbx mRNA levels in hibernating golden‐mantled ground squirrels (Spermophilus lateralis). Physiol Biochem Zool 77: 582‐593, 2004.
 474. Rouvinen‐Watt K , Mustonen AM , Conway R , Pal C , Harris L , Saarela S , Strandberg U , Nieminen P . Rapid eevelopment of fasting‐induced hepatic lipidosis in the American mink (Neovison vison): Effects of food deprivation and re‐alimentation on body fat depots, tissue fatty acid profiles, hematology and endocrinology. Lipids 45: 111‐128, 2010.
 475. Ruf T , Geiser F . Daily torpor and hibernation in birds and mammals. Biol Rev 90: 891‐926, 2015.
 476. Ruibal R . The adaptive value of bladder water in the toad, Bufo cognatus . Physiol Zool 35: 218‐223, 1962.
 477. Russeth KP , Higgins L , Andrews MT . Identification of proteins from non‐model organisms using mass spectrometry: Application to a hibernating mammal. J Proteome Res 5: 829‐839, 2006.
 478. Russom JM , Guba GR , Sanchez D , Tam CF , Lopez GA , Garcia RE . Plasma lipoprotein cholesterol concentrations in the golden‐mantled group squirrel (Spermophilus lateralis): A comparison between pre‐hibernators and hibernators. Comp Biochem Physiol B 102: 573‐578, 1992.
 479. Sandri M , Sandri C , Gilbert A , Skurk C , Calabria E , Picard A , Walsh K , Schiaffino S , Lecker SH , Goldberg AL . Foxo transcription factors induce the atrophy‐related ubiquitin ligase atrogin‐1 and cause skeletal muscle atrophy. Cell 117: 399‐412, 2004.
 480. Sapolsky RM , Romero LM , Munck AU . How do glucocorticoids influence stress responses? Integrating permissive, suppressive, stimulatory, and preparative actions. Endocrine Rev 21: 55‐89, 2000.
 481. Sartori DR , Migliorini RH , Veiga JA , Moura JL , Kettelhut IC , Linder C . Metabolic adaptations induced by long‐term fasting in quails. Comp Biochem Physiol A 111: 487‐493, 1995.
 482. Schaller G. The Serengeti Lion: A Study of Predator‐Prey Relations. Chicago and London: University of Chicago Press, 1972.
 483. Schluter J , Foster KR . The evolution of mutualism in gut microbiota via host epithelial selection. PLoS Biol 10: e1001424, 2012.
 484. Schmidt‐Nielsen K , Schmidt‐Nielsen B . Water metabolism of desert mammals 1. Physiol Rev 32: 135‐166, 1952.
 485. Scott KP , Gratz SW , Sheridan PO , Flint HJ , Duncan SH . The influence of diet on the gut microbiota. Pharmacol Res 69: 52‐60, 2013.
 486. Secor SM . Gastric function and its contribution to the postprandial metabolic response of the Burmese python Python molurus . J Exp Biol 206: 1621‐1630, 2003.
 487. Secor SM . Physiological responses to feeding, fasting and estivation for anurans. J Exp Biol 208: 2595‐2609, 2005.
 488. Secor SM . Digestive physiology of the Burmese python: Broad regulation of integrated performance. J Exp Biol 211: 3767‐3774, 2008.
 489. Secor SM . Specific dynamic action: A review of the postprandial metabolic response. J Comp Physiol B 179: 1‐56, 2009.
 490. Secor SM , Castoe TA , Pollock DD . Transcriptome analysis of the regulatory mechanisms of intestinal response for the Burmese python. Integ Comp Biol 52: E325‐E325, 2012.
 491. Secor SM , Diamond J . Adaptive responses to feeding in Burmese pythons ‐ pay before pumping. J Exp Biol 198: 1313‐1325, 1995.
 492. Secor SM , Diamond J . Determinants of the postfeeding metabolic response of Burmese pythons, Python molurus . Physiol Zool 70: 202‐212, 1997.
 493. Secor SM , Diamond J . Maintenance of digestive performance in the turtles Chelydra serpentina, Sternotherus odoratus, and Trachemys scripta . Copeia 1999: 75‐84, 1999.
 494. Secor SM , Diamond JM . Evolution of regulatory responses to feeding in snakes. Physiol Biochem Zool 73: 123‐141, 2000.
 495. Secor SM , Fehsenfeld D , Diamond J , Adrian TE . Responses of python gastrointestinal regulatory peptides to feeding. Proc Nat Acad Sci 98: 13637‐13642, 2001.
 496. Secor SM , Lignot JH . Morphological plasticity of vertebrate aestivation. Prog Mol Subcell Biol 49: 183‐208, 2010.
 497. Secor SM , Nagy KA . Bioenergetic correlates of foraging mode for the snakes Crotalus cerastes and Masticophis flagellum . Ecology 75: 1600‐1614, 1994.
 498. Secor SM , Ott BD . Adaptive correlation between feeding habits and digestive physiology for boas and pythons. In: Henderson RW, Powell R, editors. Biology of the Boas and Pythons. Eagle Mountain, Utah: Eagle Mountain Publishing LC, 2007, pp. 257‐268.
 499. Secor SM , Taylor JR , Grosell M . Selected regulation of gastrointestinal acid‐base secretion and tissue metabolism for the diamondback water snake and Burmese python. J Exp Biol 215: 185‐196, 2012.
 500. Secor SM , White SE . Prioritizing blood flow: Cardiovascular performance in response to the competing demands of locomotion and digestion for the Burmese python, Python molurus . J Exp Biol 213: 78‐88, 2010.
 501. Segner H , Dolle A , Bohm R . Ketone body metabolism in the carp Cyprinus carpio: Biochemical and 1H NMR spectroscopical analysis. Comp Biochem Physiol B 116: 257‐262, 1997.
 502. Seidel ME . Terrestrial dormancy in turtle Kinosternon flavescens ‐ respiratory metabolism and dehydration. Comp Biochem Physiol A 61: 1‐4, 1978.
 503. Seim I , Fang XD , Xiong ZQ , Lobanov AV , Huang ZY , Ma SM , Feng Y , Turanov AA , Zhu YB , Lenz TL , Gerashchenko MV , Fan DD , Yim SH , Yao XM , Jordan D , Xiong YQ , Ma Y , Lyapunov AN , Chen GX , Kulakova OI , Sun YD , Lee SG , Bronson RT , Moskalev AA , Sunyaev SR , Zhang GJ , Krogh A , Wang J , Gladyshev VN . Genome analysis reveals insights into physiology and longevity of the Brandt's bat Myotis brandtii . Nat Commun 4:2212, 2013.
 504. Seliverstova EV , Prutskova NP . Morphofunctional changes in the small intestine epithelium of the frog Rana temporaria in the course of hibernation. J Evol Biochem Physio 48: 295‐305, 2012.
 505. Serkova NJ , Rose JC , Epperson LE , Carey HV , Martin SL . Quantitative analysis of liver metabolites in three stages of the circannual hibernation cycle in 13‐lined ground squirrels by NMR. Physiol Genomics 31: 15‐24, 2007.
 506. Seymour RS . Energy metabolism of dormant spadefoot toads (Scaphiopus). Copeia 1973: 452‐460, 1973.
 507. Shao C , Liu Y , Ruan H , Li Y , Wang H , Kohl F , Goropashnaya AV , Fedorov VB , Zeng R , Barnes BM , Yan J . Shotgun proteomic analysis of hibernating arctic ground squirrels. Mol Cell Proteomics 9: 313‐326, 2010.
 508. Shapiro C , Weathers W . Metabolic and behavioral responses of American kestrels to food deprivation. Comp Biochem Physiol A 68: 111‐114, 1981.
 509. Sharon G , Garg N , Debelius J , Knight R , Dorrestein PC , Mazmanian SK . Specialized metabolites from the microbiome in health and disease. Cell Metab 20: 719‐730, 2014.
 510. Sheridan MA , Mommsen TP . Effects of nutritional state on in vivo lipid and carbohydrate metabolism of Coho Salmon, Oncorhynchus kisutch . Gen Comp Endocrinol 81: 473‐483, 1991.
 511. Shine R. Parental care in reptiles. In: Gans C, Huey RB, editors. Biology of the Reptilia. New York: Alan R. Liss, Inc, 1988, pp. 275‐329.
 512. Silverstein JT , Breininger J , Baskin DG , Plisetskaya EM . Neuropeptide Y‐like gene expression in the salmon brain increases with fasting. Gen Comp Endocrinol 110: 157‐165, 1998.
 513. Singer MA . Do mammals, birds, reptiles and fish have similar nitrogen conserving systems? Comp Biochem Physiol B 134: 543‐558, 2003.
 514. Smallwood W . Twenty months of starvation in Amia calva . Biol Bull 31: 453‐464, 1916.
 515. Snapp BD , Heller HC . Suppression of metabolism during hibernation in ground‐squirrels (Citellus lateralis). Physiol Zool 54: 297‐307, 1981.
 516. Soengas JL , Strong EF , Andres MD . Glucose, lactate, and beta‐hydroxybutyrate utilization by rainbow trout brain: Changes during food deprivation. Physiol Zool 71: 285‐293, 1998.
 517. Soengas JL , Strong EF , Fuentes J , Aldegunde M , Andres MD . Post feeding carbohydrate and ketone bodies metabolism in brain and liver of Atlantic salmon. J Physiol Biochem 52: 131‐142, 1996.
 518. Soengas JL , Strong EF , Fuentes J , Veira JAR , Andres MD . Food deprivation and refeeding in Atlantic salmon, Salmo salar: Effects on brain and liver carbohydrate and ketone bodies in metabolism. Fish Physiol Biochem 15: 491‐511, 1996.
 519. Sokolovic M , Sokolovic A , van Roomen CP , Gruber A , Ottenhoff R , Scheij S , Hakvoort TB , Lamers WH , Groen AK . Unexpected effects of fasting on murine lipid homeostasis–transcriptomic and lipid profiling. J Hepatol 52: 737‐744, 2010.
 520. Song X , K”rtner G , Geiser F . Reduction of metabolic rate and thermoregulation during daily torpor. J Comp Physiol B 165: 291‐297, 1995.
 521. Sonnenburg JL , Xu J , Leip DD , Chen CH , Westover BP , Weatherford J , Buhler JD , Gordon JI . Glycan foraging in vivo by an intestine‐adapted bacterial symbiont. Science 307: 1955‐1959, 2005.
 522. Sonoyama K , Fujiwara R , Takemura N , Ogasawara T , Watanabe J , Ito H , Morita T . Response of gut microbiota to fasting and hibernation in Syrian hamsters. Appl Environ Microbiol 75: 6451‐6456, 2009.
 523. Soria‐Milla MA . Structure of the mucosa of the small intestine proximal portion in the hibernating garden dormouse (Eliomys quercinus). Cryo‐Lett 7: 184‐193, 1986.
 524. Srere HK , Wang LCH , Martin SL . Central role for differential gene expression in mammalian hibernation. Proc Natl Acad Sci 89: 7119‐7123, 1992.
 525. Staiger H , Tschritter O , Machann J , Thamer C , Fritsche A , Maerker E , Schick F , Haring HU , Stumvoll M . Relationship of serum adiponectin and leptin concentrations with body fat distribution in humans. Obesity Res 11: 368‐372, 2003.
 526. Staples JF . Metabolic flexibility: Hibernation, torpor and estivation. Comp Physiol (in press), 2015.
 527. Starck JM , Beese K . Structural flexibility of the small intestine and liver of garter snakes in response to feeding and fasting. J Exp Biol 204: 1377‐1388, 2002.
 528. Starck JM , Cruz‐Neto AP , Abe AS . Physiological and morphological responses to feeding in broad‐nosed caiman (Caiman latirostris). J Exp Biol 210: 2033‐2045, 2007.
 529. Steffen JM , Koebel DA , Musacchia XJ , Milsom WK . Morphometric and metabolic indices of disuse in muscles of hibernating ground squirrels. Comp Biochem Physiol B 99: 815‐819, 1991.
 530. Stevenson TJ , Duddleston KN , Buck CL . Effects of season and host physiological state on the diversity, density, and activity of the arctic ground squirrel cecal microbiota. Appl Environ Microbiol 80:5611‐5622, 2014.
 531. Stonehouse B . The king penguin Aptenodytes patagonica of South Georgia. I. Breeding behaviour and development. Sci Rep Falkland Isl Depend Surv 23: 1‐81, 1960.
 532. Stonehouse B . The general biology and thermal balance of penguins. Adv Ecol Res 4: 131‐196, 1967.
 533. Storey KB . Turning down the fires of life: Metabolic regulation of hibernation and estivation. In: Storey KB, editor. Molecular Mechanisms of Metabolic Arrest: Life in Limbo. Oxford: BIOS Scientific Publishers, 2001, pp. 1‐21.
 534. Storey KB . Life in the slow lane: Molecular mechanisms of estivation. Comp Biochem Physiol A 133: 733‐754, 2002.
 535. Storey KB , Storey JM . Metabolic regulation and gene expression during aestivation. Prog Mol Subcell Biol 49: 25‐45, 2010.
 536. Streja DA , Marliss EB , Steiner G . Effects of prolonged fasting on plasma triglyceride kinetics in man. Metabolism 26: 505‐516, 1977.
 537. Sturla L , Rampal R , Haltiwanger RS , Zanardi D , Etzioni A , Tonetti M . Characterization of the residual fucose‐containing glycoconjugates in LAD II/CDGS IIc cells. Glycobiology 12: 664‐664, 2002.
 538. Suarez RK , Mommsen TP . Gluconeogenesis in teleost fishes. Can J Zool 65: 1869‐1882, 1987.
 539. Sugiura SH , Roy PK , Ferraris RP . Dietary acidification enhances phosphorus digestibility but decreases H+/K+‐ATPase expression in rainbow trout. J Exp Biol 209: 3719‐3728, 2006.
 540. Svensson E , Raberg L , Koch C , Hasselquist D . Energetic stress, immunosuppression and the costs of an antibody response. Funct Ecol 12: 912‐919, 1998.
 541. Swaner JC , Connor WE . Hypercholesterolemia of total starvation: Its mechanism via tissue mobilization of cholesterol. Am J Physiol 229: 365‐369, 1975.
 542. Symonds BL , James RS , Franklin CE . Getting the jump on skeletal muscle disuse atrophy: Preservation of contractile performance in aestivating Cyclorana alboguttata (Gunther 1867). J Exp Biol 210: 825‐835, 2007.
 543. Tashima L , Cahill GF, Jr . Effects of insulin in the toadfish, Opsanus tau . Gen Comp Endocrinol 11: 262‐271, 1968.
 544. Tashima LS , Adelstein SJ , Lyman CP . Radioglucose utilization by active, hibernating, and arousing ground squirrels. Am J Physiol 218: 303‐309, 1970.
 545. Templeman W , Andrews GL . Jellied condition in the American plaice Hippoglossoides platessoides (Fabricius). J Fish Res Bd Can 13: 147‐182, 1956.
 546. Tessier SN , Storey KB . Expression of myocyte enhancer factor‐2 and downstream genes in ground squirrel skeletal muscle during hibernation. Mol Cell Biochem 344: 151‐162, 2010.
 547. Thorpe A , Ince BW . Plasma insulin levels in teleosts determined by a charcoal‐separation radioimmunoassay technique. Gen Comp Endocrinol 30: 332‐339, 1976.
 548. Thorson T , Svihla A . Correlation of the habitats of amphibians with their ability to survive the loss of body water. Ecology 24: 374‐381, 1943.
 549. Tian J , Wen H , Zeng LB , Jiang M , Wu F , Liu W , Yang CG . Changes in the activities and mRNA expression levels of lipoprotein lipase (LPL), hormone‐sensitive lipase (HSL) and fatty acid synthetase (FAS) of Nile tilapia (Oreochromis niloticus) during fasting and re‐feeding. Aquaculture 400: 29‐35, 2013.
 550. Tinker DB , Harlow HJ , Beck TD . Protein use and muscle‐fiber changes in free‐ranging, hibernating black bears. Physiol Zool 71: 414‐424, 1998.
 551. Toien O , Blake J , Edgar DM , Grahn DA , Heller HC , Barnes BM . Hibernation in black bears: Independence of metabolic suppression from body temperature. Science 331: 906‐909, 2011.
 552. Totzke U , Fenske M , Huppop O , Raabe H , Schach N . The influence of fasting on blood and plasma composition of herring gulls (Larus argentatus). Physiol Biochem Zool 72: 426‐437, 1999.
 553. Trautman MB , Bills WE , Wickliff EL . Winter losses from starvation and exposure of waterfowl and upland game birds in Ohio and other northern states. Wilson Bull 51: 86‐104, 1939.
 554. Tyler MJ , Carter DB . Oral birth of the young of the gastric brooding frog Rheobatrachus silus . Anim Behav 29: 280‐282, 1981.
 555. Tyler MJ , Shearman DJ , Franco R , O'Brien P , Seamark RF , Kelly R . Inhibition of gastric acid secretion in the gastric brooding frog, Rheobatrachus silus . Science 220: 609‐610, 1983.
 556. Ullrey DE . Seasonal starvation in northern white‐tailed deer. In: McCue MD , editor. Comparative Physiology of Fasting, Starvation, and Food Limitation. Berlin: Springer‐Verlag, 2012, pp. 297‐307.
 557. Ultsch GR . Ecology and physiology of hibernation and overwintering among freshwater fishes, turtles, and snakes. Biol Rev 64: 435‐516, 1989.
 558. Unniappan S , Peter RE . Structure, distribution and physiological functions of ghrelin in fish. Comp Biochem Physiol A 140: 396‐408, 2005.
 559. Uriona TJ , Farmer CG , Dazely J , Clayton F , Moore J . Structure and function of the esophagus of the American alligator (Alligator mississippiensis). J Exp Biol 208: 3047‐3053, 2005.
 560. Utz JC , Nelson S , O'Toole BJ , van Breukelen F . Bone strength is maintained after 8 months of inactivity in hibernating golden‐mantled ground squirrels, Spermophilus lateralis . J Exp Biol 212: 2746‐2752, 2009.
 561. van Beurden EK . Energy metabolism of dormant Australian water‐holding frogs (Cyclorana platycephalus). Copeia 1980: 787‐799, 1980.
 562. Van Beurden EK . Survival strategies of the Australian water‐holding frog, Cyclorana platycephalus. In: Cogger HG, Cameron EE, editors. Arid Australia. Sydney: Australian Museum, 1984, pp. 223‐234.
 563. van Breukelen F , Martin SL . Translational initiation is uncoupled from elongation at 18 degrees C during mammalian hibernation. Am J Physiol Regul Integr Comp Physiol 281: R1374‐R1379, 2001.
 564. van Breukelen F , Martin SL . Reversible depression of transcription during hibernation. J Comp Physiol B 172: 355‐361, 2002.
 565. Van der Geyten S , Mol KA , Pluymers W , Kuhn ER , Darras VM . Changes in plasma T‐3 during fasting/refeeding in tilapia (Oreochromis niloticus) are mainly regulated through changes in hepatic type II iodothyronine deiodinase. Fish Physiol Biochem 19: 135‐143, 1998.
 566. Veeneman JM , Kingma HA , Stellaard F , de Jong PE , Reijngoud DJ , Huisman RM . Comparison of amino acid oxidation and urea metabolism in haemodialysis patients during fasting and meal intake. Nephrol Dial Transplant 19: 1533‐1541, 2004.
 567. Verrier D , Groscolas R , Guinet C , Arnould JP . Physiological response to extreme fasting in subantarctic fur seal (Arctocephalus tropicalis) pups: Metabolic rates, energy reserve utilization, and water fluxes. Am J Physiol Regul Integr Comp Physiol 297: R1582‐R1592, 2009.
 568. Viscarra JA , Champagne CD , Crocker DE , Ortiz RM . 5'AMP‐activated protein kinase activity is increased in adipose tissue of northern elephant seal pups during prolonged fasting‐induced insulin resistance. J Endocrinol 209: 317‐325, 2011.
 569. Viscarra JA , Ortiz RM . Cellular mechanisms regulating fuel metabolism in mammals: Role of adipose tissue and lipids during prolonged food deprivation. Metabolism 62: 889‐897, 2013.
 570. Viscarra JA , Rodriguez R , Vazquez‐Medina JP , Lee A , Tift MS , Tavoni SK , Crocker DE , Ortiz RM . Insulin and GLP‐1 infusions demonstrate the onset of adipose‐specific insulin resistance in a large fasting mammal: Potential glucogenic role for GLP‐1. Physiol Rep 1: e00023, 2013.
 571. Viscarra JA , Vazquez‐Medina JP , Crocker DE , Ortiz RM . Glut4 is upregulated despite decreased insulin signaling during prolonged fasting in northern elephant seal pups. Am J Physiol Regul Integr Comp Physiol 300: R150‐R154, 2011.
 572. Walker BH , Emslie RH , Owensmith RN , Scholes RJ . To cull or not to cull ‐ lessons from a southern african drought. J Appl Ecol 24: 381‐401, 1987.
 573. Wang L , Llorente C , Hartmann P , Yang AM , Chen P , Schnabl B . Methods to determine intestinal permeability and bacterial translocation during liver disease. J Immunolog Methods 421: 44‐53, 2015.
 574. Wang T , Hung CC , Randall DJ . The comparative physiology of food deprivation: From feast to famine. Annu Rev Physiol 68: 223‐251, 2006.
 575. Wenberg GM , Holland JC . The circannual variations in the total serum lipids and cholesterol with respect to body weight in the woodchuck (Marmota monax). Comp Biochem Physiol A 44: 577‐583, 1973.
 576. West TG , Donohoe PH , Staples JF , Askew GN . Tribute to R. G. Boutilier: The role for skeletal muscle in the hypoxia‐induced hypometabolic responses of submerged frogs. J Exp Biol 209: 1159‐1168, 2006.
 577. Wickler SJ , Hoyt DF , van Breukelen F . Disuse atrophy in the hibernating golden‐mantled ground squirrel, Spermophilus lateralis . Am J Physiol Regul Integr Comp Physiol 261: R1214‐R1217, 1991.
 578. Williams AJ , Siegfried WR , Burger AE , Berruti A . Body composition and energy metabolism of moulting eudyptid penguins. Comp Biochem Physiol A 56: 27‐30, 1977.
 579. Williams CT , Goropashnaya AV , Buck CL , Fedorov VB , Kohl F , Lee TN , Barnes BM . Hibernating above the permafrost: Effects of ambient temperature and season on expression of metabolic genes in liver and brown adipose tissue of arctic ground squirrels. J Exp Biol 214: 1300‐1306, 2011.
 580. Williams DR , Epperson LE , Li W , Hughes MA , Taylor R , Rogers J , Martin SL , Cossins AR , Gracey AY . Seasonally hibernating phenotype assessed through transcript screening. Physiol Genomics 24: 13‐22, 2005.
 581. Wilson S , Swan G . Reptiles of Australia. Princeton: Princeton Field Guides, 2003.
 582. Wilz M , Heldmaier G . Comparison of hibernation, estivation and daily torpor in the edible dormouse, Glis glis . J Comp Physiol B 170: 511‐521, 2000.
 583. Winne CT , Willson JD , Gibbons JW . Income breeding allows an aquatic snake Seminatrix pygaea to reproduce normally following prolonged drought‐induced aestivation. J Anim Ecol 75: 1352‐1360, 2006.
 584. Withers PC , Cooper CE . Metabolic depression: A historical perspective. Prog Mol Subcell Biol 49: 1‐23, 2010.
 585. Withers PC , Guppy M . Do Australian desert frogs co‐accumulate counteracting solutes with urea during aestivation? J Exp Biol 199: 1809‐1816, 1996.
 586. Wobeser G , Kost W . Starvation, staphylococcosis, and vitamin A deficiency among mallards overwintering in Saskatchewan. J Wildlife Dis 28: 215‐222, 1992.
 587. Wojda SJ , McGee‐Lawrence ME , Gridley RA , Auger J , Black HL , Donahue SW . Yellow‐bellied marmots (Marmota flaviventris) preserve bone strength and microstructure during hibernation. Bone 50: 182‐188, 2012.
 588. Worthy GAJ , Lavigne DM . Mass loss, metabolic rate, and energy utilization by harp and gray seal pups during the postweaning fast. Physiol Zool 60: 352‐364, 1987.
 589. Worthy GAJ , Morris PA , Costa DP , Leboeuf BJ . Molt energetics of the northern elephant seal (Mirounga angustirostris). J Zool 227: 257‐265, 1992.
 590. Xia JH , Lin G , Fu GH , Wan ZY , Lee M , Wang L , Liu XJ , Yue GH . The intestinal microbiome of fish under starvation. BMC Genomics 15: 266, 2014.
 591. Xu J , Gordon JI . Honor thy symbionts. Proc Natl Acad Sci U S A 100: 10452‐10459, 2003.
 592. Xu R , Andres‐Mateos E , Mejias R , Macdonald EM , Leinwand LA , Merriman DK , Fink RH , Cohn RD . Hibernating squirrel muscle activates the endurance exercise pathway despite prolonged immobilization. Exp Neurol 247: 392‐401 2013.
 593. Xu Y , Shao C , Fedorov VB , Goropashnaya AV , Barnes BM , Yan J . Molecular signatures of mammalian hibernation: Comparisons with alternative phenotypes. BMC Genomics 14: 567, 2013.
 594. Yan J , Barnes BM , Kohl F , Marr TG . Modulation of gene expression in hibernating arctic ground squirrels. Physiol Genomics 32: 170‐181, 2008.
 595. Yan J , Burman A , Nichols C , Alila L , Showe LC , Showe MK , Boyer BB , Barnes BM , Marr TG . Detection of differential gene expression in brown adipose tissue of hibernating arctic ground squirrels with mouse microarrays. Physiol Genomics 25: 346‐353, 2006.
 596. Young I , Malozowski S , Winterer J , Nicoletti MC , Kibarian M , Cassorla F . Acute starvation affects rat adrenal steroidogenesis. Horm Metabolic Res 19: 21‐23, 1987.
 597. Young TP . Natural die offs of large mammals ‐ implications for conservation. Conservation Biol 8: 410‐418, 1994.
 598. Young VR , Munro HN . Ntau‐methylhistidine (3‐methylhistidine) and muscle protein turnover: An overview. FASEB J 37: 2291‐2300, 1978.
 599. Youngberg CA , Wlodyga J , Schmaltz S , Dressman JB . Radiotelemetric determination of gastrointestinal pH in 4 healthy beagles. Am J Veterinary Res 46: 1516‐1521, 1985.
 600. Yufera M , Moyano FJ , Astola A , Pousao‐Ferreira P , Martinez‐Rodriguez G . Acidic digestion in a teleost: Postprandial and circadian pattern of gastric pH, pepsin activity, and pepsinogen and proton pump mRNAs expression. PLoS One 7: e33687, 2012.
 601. Zammit VA , Newsholme EA . Activities of enzymes of fat and ketone‐body metabolism and effects of starvation on blood concentrations of glucose and fat fuels in teleost and elasmobranch fish. Biochem J 184: 313‐322, 1979.
 602. Zeng LQ , Li FJ , Li XM , Cao ZD , Fu SJ , Zhang YG . The effects of starvation on digestive tract function and structure in juvenile southern catfish (Silurus meridionalis Chen). Comp Biochem Physiol A 162: 200‐211, 2012.
 603. Zhan XM , Li YL , Wang DH . Effects of fasting and refeeding on body mass, thermogenesis and serum leptin in Brandt's voles (Lasiopodomys brandtii). J Therm Biol 34: 237‐243, 2009.
 604. Zhegunov GF , Mikulinsky YE , Kudokotseva EV . Hyperactivation of protein synthesis in tissues of hibernating animals on arousal. Cryo‐Lett 9: 236‐245, 1988.
 605. Zimny ML , Tyrone V . Carbohydrate metabolism during fasting and hibernation in the ground squirrel. Am J Physiol 189: 297‐300, 1957.

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Article Title: Integrative Physiology of Fasting
 

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Stephen M. Secor, Hannah V. Carey. Integrative Physiology of Fasting. Compr Physiol 2016, null: 773-825. doi: 10.1002/cphy.c150013