Is re-feeding efficiency compromised by prolonged starvation during aestivation in the green striped burrowing frog, Cyclorana alboguttata?

We examined several morphological parameters of the gastrointestinal tract, digesta passage rates, and nutrient assimilation efficiencies of Green-striped Burrowing frogs (Cyclorana alboguttata) following prolonged fasting during three months of aestivation and compared these with frogs that had been continuously fed. Whole animal digesta passage rates were significantly reduced following three months aestivation as a result of a decreased digesta evacuation rate from the stomach. Furthermore, food was selectively retained in the small intestine for an increased time following three months of aestivation. Overall digestibility of food and nitrogen, carbon, and energy extraction efficiencies were not significantly different from control values following three months of aestivation. These findings suggest that C. alboguttata employs reduced digesta passage rates so as to maximize nutrient assimilation efficiency following prolonged food deprivation during aestivation.     

Arousal and re-feeding rapidly restores digestive tract morphology following aestivation in green-striped burrowing frogs

During aestivation, the gut of the green-striped burrowing frog, Cyclorana alboguttata undergoes significant morphological down-regulation. Despite the potential impact such changes might have on the re-feeding efficiency of these animals following aestivation, they appear to be as efficient at digesting their first meals as active, non-aestivating animals. Such efficiency might come about by the rapid restoration of intestinal morphology with both arousal from aestivation and the initial stages of re-feeding. Consequently, this study sought to determine what morphological changes to the intestine accompany arousal and re-feeding following 3 months of aestivation. Arousal from aestivation alone had a marked impact on many morphological parameters, including small and large intestine masses, small intestinal length, LF heights, enterocyte cross-sectional area and microvilli height and density. In addition, the onset of re-feeding was correlated with an immediate reversal of many morphological parameters affected by 3 months of aestivation. Those parameters that had not returned to control levels within 36 h of feeding generally had returned to control values by the completion of digestion (i.e. defecation of the meal). Re-feeding was also associated with several changes in enterocyte morphology including the incorporation in intracytoplasmic lipid droplets and the return of enterocyte nuclear material to the 'active' euchromatin state. In conclusion, morphological changes to the gut of aestivating frogs which occur during aestivation are transitory and rapidly reversible with both arousal from aestivation and re-feeding. The proximate causes behind these transitions and their functional significance are discussed.     

Metabolic depression during aestivation in Cyclorana alboguttata

The green striped burrowing frog, Cyclorana alboguttata, spends, on average, nine to ten months of every year in aestivation. Recently, C. alboguttata has been the focus of much investigation regarding the physiological processes involved in aestivation, yet our understanding of this frog's capacity to metabolically depress remains limited. This study aimed to extend our current knowledge of metabolic depression during aestivation in C. alboguttata. C. alboguttata reduced whole animal metabolism by 82% within 5 weeks of aestivation. The effects of aestivation on mass specific in vitro tissue metabolic rate (VO₂) varied among individual organs, with muscle and liver slices showing significant reductions in metabolism; kidney VO₂ was elevated and there was no change in the VO₂ of small intestine tissue slices. Organ size was also affected by aestivation, with significant reductions in the mass of all tissues, except the gastrocnemius. These reductions in organ size, combined with changes in mass specific VO₂ of tissue slices, resulted in further energy savings to aestivating animals. This study shows that C. alboguttata is capable of selectively down- or up-regulating individual tissues, using both changes in metabolic rate and morphology. This strategy allows maximal energy savings during aestivation without compromising organ functionality and survival at arousal.     

Hot and steady: Elevated temperatures do not enhance muscle disuse atrophy during prolonged aestivation in the ectotherm Cyclorana alboguttata

Animals that undergo prolonged dormancy experience minimal muscle disuse atrophy (MDA) compared to animals subjected to artificial immobilisation over shorter timeframes. An association between oxidative stress and MDA suggests that metabolic depression presumably affords dormant animals some protection against muscle disuse. Because aerobic metabolism is temperature sensitive, we proposed that MDA in dormant (aestivating) ectotherms would be enhanced at elevated temperatures. In the green‐striped burrowing frog, Cyclorana alboguttata, the thermal sensitivity of skeletal muscle metabolic rate is muscle‐specific. We proposed that the degree of atrophy experienced during aestivation would correlate with the thermal sensitivity of muscle metabolic rate such that muscles with a relatively high metabolic rate at high temperatures would experience more disuse atrophy. To test this hypothesis, we examined the effect of temperature and aestivation on the extent of MDA in two functionally different muscles: the M. gastrocnemius (jumping muscle) and M. iliofibularis (non‐jumping muscle), in C. alboguttata aestivating at 24 or 30°C for 6 months. We compared a range of morphological parameters from muscle cross‐sections stained with succinic dehydrogenase to show that muscle‐specific patterns of disuse atrophy were consistent with the relative rates of oxygen consumption of those muscle types. However, despite muscle‐specific differences in thermal sensitivity of metabolic rate, aestivation temperature did not influence the extent of atrophy in either muscle. Our results suggest that the muscles of frogs aestivating at high temperatures are defended against additional atrophy ensuring protection of muscle function during long periods of immobilisation. J. Morphol., 2013. © 2012 Wiley Periodicals, Inc.     

Changes in the small intestine of Schistosoma mansoni-infected mice fed a high-fat diet

The consumption of a high-fat diet modifies both the morphology of the small intestine and experimentally tested effects of schistosomiasis mansoni. However, whether a schistosomiasis infection associated with a high-fat diet causes injury to the small intestine has never been investigated. Mice were fed either a high-fat or a standard-fat diet for 6 months and were then infected with Schistosoma mansoni cercariae. Physical characteristics of the intestinal tissue (mucosal thickness, small intestinal villi length and height, and abundance of goblet cells and enterocytes on the villous surface) and the distribution of granulomas along the intestinal segments and their developmental stage were measured at the time of sacrifice (9 or 17 weeks post-infection). The group fed a high-fat diet exhibited different granuloma stages, whereas the control group possessed only exudative granulomas. The chronically infected mice fed a high-fat diet exhibited higher granuloma and egg numbers than the acutely infected group. Exudative, exudative/exudative-productive and exudative-productive granulomas were present irrespective of diet. Computer-aided morphometric analysis confirmed that villus length, villus width, muscular height and submucosal height of the duodenal and jejunal segments were affected by diet and infection. In conclusion, a high-fat diet and infection had a significant impact on the small intestine morphology and morphometry among the animals tested.     

The interplay of increased urea synthesis and reduced ammonia production in the African lungfish Protopterus aethiopicus during 46 days of aestivation in a mucus cocoon

This study was undertaken to test the hypothesis that the rate of urea synthesis in Protopterus aethiopicus was up-regulated to detoxify ammonia during the initial phase of aestivation in air (day 1-day 12), and that a profound suppression of ammonia production occurred at a later phase of aestivation (day 35-day 46) which eliminated the need to sustain the increased rate of urea synthesis. Fasting apparently led to a greater rate of nitrogenous waste excretion in P. aethiopicus in water, which is an indication of increases in production of endogenous ammonia and urea probably as a result of increased proteolysis and amino acid catabolism for energy production. However, 46 days of fasting had no significant effects on the ammonia or urea contents in the muscle, liver, plasma and brain. In contrast, there were significant decreases in the muscle ammonia content in fish after 12, 34 or 46 days of aestivation in air when compared with fish fasting in water. Ammonia was apparently detoxified to urea because urea contents in the muscle, liver, plasma and brain of P. aethiopicus aestivated for 12, 34 or 46 days were significantly greater than the corresponding fasting control; the greatest increases in urea contents occurred during the initial 12 days. There were also significant increases in activities of some of the hepatic ornithine-urea cycle enzymes from fish aestivated for 12 or 46 days. Therefore, contrary to a previous report on P. aethiopicus, our results demonstrated an increase in the estimated rate of urea synthesis (2.8-fold greater than the day 0 fish) in this lungfish during the initial 12 days of aestivation. However, the estimated rate of urea synthesis decreased significantly during the next 34 days. Between day 35 and day 46 (12 days), urea synthesis apparently decreased to 42% of the day 0 control value, and this is the first report of such a phenomenon in African lungfish undergoing aestivation. On the other hand, the estimated rate of ammonia production in P. aethiopicus increased slightly (14.7%) during the initial 12 days of aestivation as compared with that in the day 0 fish. By contrast, the estimated rate of ammonia production decreased by 84% during the final 12 days of aestivation (day 35-day 46) compared with the day 0 value. Therefore, it can be concluded that P. aethiopicus depended mainly on increased urea synthesis to ameliorate ammonia toxicity during the initial phase of aestivation, but during prolonged aestivation, it suppressed ammonia production profoundly, eliminating the need to increase urea synthesis which is energy-intensive.     

Conjugated linoleic acids differentially alter polyp number and diameter in the Apc(min/+) mouse model of intestinal cancer

Abstract.   Objective:  Dietary conjugated linoleic acids (CLA) have had many health benefits claimed for them, including antineoplastic actions. Materials and methods:  The effects of the predominant forms of CLA, namely the c9t11 and t10c12 isomers, or a mixture of these on polyp development, were investigated in the Apc ^Min/+ mouse. CLAs have also been linked to altered rates of cell renewal and cell proliferation so this was also studied, as was a further means of increasing tissue mass, namely crypt fission. Results:  The stomach and small intestine were significantly heavier in the t10c12, and in the mixture-treated groups ( P <  0.001). Crypt fission was increased in the middle small intestine by the t10c12 diet while colonic weight was reduced by c9t11 provision and crypts were 20% shorter. The t10c12 and the mixture significantly reduced polyp number in the proximal small intestine but they increased polyp diameter in the middle and distal small intestine, to an extent that the polyp burden was significantly increased at these sites. All CLAs significantly reduced polyp number in the colon, but the mixture significantly increased polyp diameter in the colon. Conclusion : Increased polyp diameter associated with t10c12 diet and especially with the mixture is a cause of concern, as this is the commercially available form. The naturally occurring isomer, c9t11 decreased colonic polyp number and did not increase diameter, suggesting that this natural isomer is the most likely to be protective.     

Effect of aestivation on muscle characteristics and locomotor performance in the Green-striped burrowing frog, Cyclorana alboguttata

The Green-striped burrowing frog, Cyclorana alboguttata survives extended drought periods by burrowing underground and aestivating. These frogs remain immobile within cocoons of shed skin and mucus during aestivation and emerge from their burrows upon heavy rains to feed and reproduce. Extended periods of immobilisation in mammals typically result in muscle atrophy and a decrease in muscle performance. We examined the effect of aestivation and hence prolonged immobilisation, on skeletal muscle mass, in vitro muscle performance, and locomotor performance in C. alboguttata. Frogs were aestivated in soil for 3 months and were compared with control animals that remained active, were fed, and had a continual supply of water. Compared to the controls, the wet mass of the gastrocnemius, sartorius, gracilus major, semimembranosus, peroneus, extensor cruris, tibialis posticus and tibialis anticus longus of aestivators remained unchanged indicating no muscle atrophy. The in-vitro performance characteristics of the gastrocnemius muscle were maintained and burst swimming speed was unaffected, requiring no recovery from the extended period of immobilisation associated with aestivation. This preservation of muscle size, contractile condition and locomotor performance through aestivation enables C. alboguttata to compress their life history into unpredictable windows of opportunity, whenever heavy rains occur.     

Water content, body weight and acid mucopolysaccharides, hyaluronidase and beta-glucuronidase in response to aestivation in Australian desert frogs

This study investigates the effects of aestivation on body water content, body mass, acid mucopolysaccharide (AMPS) and some of its degrading enzymes in different tissues for some Australian desert frogs. The AMPS component of the liver, kidney, skin and cocoon alter during aestivation to help retain water, which is unchanged in most tissues of all frog species, and to protect the frogs from desiccation during extended periods of aestivation. Hepatic AMPS was unaltered in Cyclorana maini, C. platycephala and Neobatrachus sutor but increased significantly after 2 months of aestivation in C. australis. The level of AMPS in the kidney was elevated in all four frog species after 5 months of aestivation. Skin AMPS content in the skin of awake frogs decreases with aestivation period and increases in the cocoon. AMPS in the cocoon probably works as a cement between the cocoons' layers and its physical presence presumably contributes to preventing water flux. Changes in AMPS content in different tissues were accompanied by significant changes in both hyaluronidase and beta-glucuronidase activities, which play an important role in AMPS metabolism. Alcian blue staining of control and digested skin of C. australis and C. platycephala with testicular hyaluronidase indicated the presence of AMPS, concentrated in a thin layer (called ground substance, GS) located between stratum compactum and stratum spongiosum, and acid mucin concentrated in the mucous glands and in a 'tubular' structure which could be observed in the epidermal layer. Hyaluronidase digestion of the cocoon slightly changed the Alcian Blue colour, suggesting the presence of a large amount of acid mucin similar to that found in the skin mucous gland. The results of this study present data for the redistribution of AMPS, which may help in reducing water loss across the cocoon and reabsorption of water in the kidney during aestivation.     

Enzyme activity in the aestivating Green-striped burrowing frog (Cyclorana alboguttata)

Green-striped burrowing frogs (Cyclorana alboguttata) can depress their resting metabolism by more than 80% during aestivation. Previous studies have shown that this species is able to withstand long periods of immobilisation during aestivation while apparently maintaining whole muscle mass and contractile performance. The aim of this study was to determine the effect of prolonged aestivation on the levels of metabolic enzymes (CCO, LDH and CS) in functionally distinct skeletal muscles (cruralis, gastrocnemius, sartorius, iliofibularis and rectus abdominus) and liver of C. alboguttata. CS activity was significantly reduced in all tissues except for the cruralis, gastrocnemius and the liver. LDH activity was significantly reduced in the sartorius and rectus abdominus, but remained at control (active) levels in the other tissues. CCO activity was significantly reduced in the gastrocnemius and rectus abdominus, and unchanged in the remaining tissues. Muscle protein was significantly reduced in the sartorius and iliofibularis during aestivation, and unchanged in the remaining muscles. The results suggest that the energy pathways involved in the production and consumption of ATP are remodelled during prolonged aestivation but selective. Remodelling and subsequent down-regulation of metabolic activity seem to target the smaller non-jumping muscles, while the jumping muscles retain enzyme activities at control levels during aestivation. These results suggest a mechanism by which aestivating C. alboguttata are able to maintain metabolic depression while ensuring that the functional capacity of critical muscles is not compromised upon emergence from aestivation.     

Effect of fasting in the digestive system: Histological study of the small intestine in house sparrows

In birds and mammals the metabolic response to fasting has been studied and can be characterized by three consecutive phases reflecting metabolic and physiological adjustments. An effective way to minimize energy expenditure during food scarcity is to decrease the mass of the organs. As the digestive system is metabolically expensive to maintain, the small intestine and the liver are the most affected organs. We evaluated the effects of phase III starvation on the mass of the different organs and histological parameters on house sparrows, a small non-migrant bird. In a short period of time (34 h) we observed a larger reduction in the digestive organ mass when compared to the mass of the body and non-alimentary tissues. Furthermore, the intestinal mass was proportionally more reduced than its length and nominal surface area. A reduction on the intestinal mucosal layer also resulted in a shortening of villus (length and thickness) and crypt depth. Moreover, the morphology of the enterocytes changed from cylindrical to cubical, suggesting that the surface exposed to the lumen was conserved. This may indicate an adaptive response to the moment of refeeding. The nominal surface area/body mass remained constant in both groups and several histological parameters were reduced, suggesting that starving induces the atrophy of the small intestine. However, the goblet cells were conserved after fasting indicating a protective tendency.     

Metabolic depression and Na+/K+ gradients in the aestivating Australian goldfields frog,Neobatrachus wilsmorei

During aestivation the metabolic rate of the Australian goldfields frog Neobatrachus wilsmorei was reduced by 80% from its standard metabolic rate. The in vitro rate of oxygen consumption of isolated muscle and skin from aestivating frogs was up to 50% lower than that of the non-aestivating frogs. This in vitro rate of oxygen consumption was maintained for 6–12 h, indicating an intrinsic metabolic depression of tissues during aestivation. Frogs became dehydrated during aestivation. Muscle, skin and liver also became dehydrated during aestivation, but brain and kidney did not. Na⁺ and K⁺ contents and extracellular space measurement for muscle indicated that ion gradients were maintained across the muscle cell membrane during aestivation. Increases in plasma concentrations of Na⁺ and K⁺ were matched with similar increases in muscle intracellular ion concentrations. Extracellular space measurements were unsuccessful in the other tissues, but K⁺ content in all tissues (per dry weight) was maintained during aestivation, and the concentration of plasma K⁺ did not increase above that which can be accounted for by dehydration, indicating that K⁺ gradients were maintained.Abbreviations bm body mass - DPM disintegrations per minute - dw dry weight - MR metabolic rate - vO₂ rate of oxygen consumption - ww wet weight     

Metabolic depression during aestivation does not involve remodelling of membrane fatty acids in two Australian frogs

Changes in membrane lipid composition (membrane remodelling) have been associated with metabolic depression in some aestivating snails but has not been studied in aestivating frogs. This study examined the membrane phospholipid composition of two Australian aestivating frog species Cyclorana alboguttata and Cyclorana australis. The results showed no major membrane remodelling of tissue in either frog species, or in mitochondria of C. alboguttata due to aestivation. Mitochondrial membrane remodelling was not investigated in C. australis. Where investigated in C. alboguttata, total protein and phospholipid content, and citrate synthase (CS) and cytochrome c oxidase (CCO) activities in tissues and mitochondria mostly did not change with aestivation in liver. In skeletal muscle, however, CS and CCO activities, mitochondrial and tissue phospholipids, and mitochondrial protein decreased with aestivation. These decreases in muscle indicate that skeletal muscle mitochondrial content may decrease during aestivation. Na⁺K⁺ATPase activity of both frog species showed no effect of aestivation. In C. alboguttata different fat diets had a major effect on both tissue and mitochondrial phospholipid composition indicating an ability to remodel membrane composition that is not utilised in aestivation. Therefore, changes in lipid composition associated with some aestivating snails do not occur during aestivation in these Australian frogs.     

Immune responses and intestinal morphology of striped catfish,Pangasianodon hypophthalmus (Sauvage, 1878), fed dietary nucleotides

The present study was conducted to evaluate the effects of dietary nucleotides (NT) on growth performance, immune responses, and intestinal morphology of striped catfish, Pangasianodon hypophthalmus. Different levels of NT (0, 0.25. 0.5, 0.75, and 1% weight per weight, WW^?1) were used in the basal diet and then randomly allocated to triplicate groups of fish with an average initial weight of 1.52 ± 0.11 g for 10 weeks. Nucleotide supplementation did not improve growth parameters significantly (P > 0.05). Feeding fish with a NT‐containing diet significantly improved ACH₅₀ activity and IgM levels in comparison to the control group (P < 0.05). The dietary NT (P < 0.05) affected the intestinal morphology, whereby the folds and enterocyte heights in the mid‐intestine were significantly increased compared to the control group (P < 0.05), while the microvilli length was not affected. The results indicate that feeding striped catfish with commercial NT have significant effects on the immune parameters and intestinal morphology of catfish and that the best NT levels are 0.25 and 0.5%.     

禁食和重喂食对大绒鼠消化道长度与重量的影响

为探讨禁食和重喂食对栖息于横断山地区大绒鼠(Eothenomys miletus)消化道形态的影响,对禁食和重喂食条件下大绒鼠消化道各项指标进行了测定.实验分别测定了大绒鼠禁食12h、24 h、36 h和重喂食12 h、48 h、7d后的总消化道、胃、小肠、大肠、盲肠的长度及其含内容物重、去内容物重、干重.结果表明:禁食后,总消化道含内容物重、胃含内容物重和胃去内容物重增加,重喂食7d后均恢复到对照组水平.小肠含内容物重在禁食12h时最大,在重喂食12h时最小,重喂食48 h后恢复到对照组水平.禁食和重喂食条件下,大绒鼠的大肠和盲肠各指标均没有显著变化.以上结果表明,大绒鼠在食物受到限制、饥饿等胁迫因子作用下,可能通过调节消化道形态来满足部分能量需求,维持正常的生理机能.大绒鼠的消化道在禁食和重喂食中表现出的变化模式,可能与其食物资源时常波动的野外生存环境有关,从一方面反映了该物种在食物胁迫下的生存机制和适应对策.     

Effect of fasting on the structure and function of the gastrointestinal tract of house sparrows (Passer domesticus)

Starvation is a condition that often affects animals in nature. The gastrointestinal tract is the organ system displaying the most rapid and dramatic changes in response to nutrient deprivation. To date, little is known about starvation phases and effects on the organ morphology and digestive function in small passerine birds. In this study, we determined the phases of starvation and examined the effect of final stage of starvation in the organ morphology and, intestinal histology and enzymatic function in the small intestine. Our results show the three phases of the classical model of fasting in a shorter period of time. The mass of heart, pancreas, stomach, small intestine and liver of long-term fasted birds was reduced between 20 and 47%. The mass decrease in small intestine was correlated with reduction in small intestinal histology: perimeter, mucosal thickness, villus height and width. In contrast, the enzyme activity of sucrase-isomaltase and aminopeptidase-N in enterocytes, all expressed per μg of protein, was higher in long-term fasted birds than fed animals. This suggest that, while autophagy of digestive organs is induced by starvation, consistent with phenotypic plasticity, the activity of sucrase-isomaltase and aminopeptidase-N remains high, probably as an anticipatory strategy to optimize digestion at re-feeding time.     

Nuclear ribonucleoprotein complexes of amphibian liver. II. Changes in the protein moiety during development.

Ribonucleoprotein complexes composed of small molecular weight nuclear RNA (4--9 S) and proteins were isolated from hepatic nuclei of Rana catesbeiana (bullfrog) and the protein moiety of this nuclear ribonucleoprotein complex compared during different stages of development. SDS-polyacrylamide gel analysis of premetamorphic tadpoles and adult frog nuclear ribonucleoprotein complexes revealed that while the protein profiles of these two particles were very similar polypeptides of 47,000, 70,000, and 11,000 molecular weight were present in significantly higher concentrations in the frog ribonucleoprotein complexes. Comparison of the chromatin proteins isolated from these two developmental stages demonstrated that these three polypeptides of frog ribonucleoprotein were not contaminants from chromatin. Since these three polypeptides could not be preferentially extracted from the frog ribonucleoprotein complex by 0.5 M KCl or 1 M urea, it was unlikely that these polypeptides were bound nonspecifically to the ribonucleoprotein particle. Polypeptide analysis of the nuclear ribonucleoprotein complexes isolated from tadpoles immersed in the thyroid hormone L-thyroxine revealed an increase in two polypeptides of 37,000 and 45,000 molecular weight during metamorphosis. The absence of reduced amount of these two polypeptides in either the premetamorphic tadpole or adult frog demonstrated that their presence in Rana catesbeiana nuclear ribonucleoprotein was transient during development and specifically associated with tadpole metamorphosis. We conclude from these experiments that the nuclear ribonucleoprotein complex is a dynamic structure during Rana catesbeiana development and that specific changes in its protein composition are associated with discrete stages of amphibian development.     

Carbohydrate and amino acid metabolism in fasting and aestivating African lungfish (Protopterus dolloi)

The potential importance of carbohydrates and amino acids as fuels during periods of fasting and aestivation in the African lungfish, Protopterus dolloi, were examined. No significant decreases in tissue glycogen levels were observed following 60 days of fasting or aestivation, suggesting lungfish may undergo 'glycogen sparing'. Yet glycogenolysis may be important during aestivation based on the differing responses of two flux-generating enzymes of the glycolytic pathway, hexokinase (HK) and pyruvate kinase (PK). PK is required for glycogen breakdown whereas HK is not. HK activity is significantly down-regulated in the heart and gill tissues during aestivation, while PK activity is sustained. The significant negative correlation between the activity of HK and glucose levels in the heart of aestivating lungfish suggests HK may be regulated by glucose concentrations. There was no indication of anaerobic glycolytic flux during aestivation as lactate did not accumulate in any of the tissues examined, and no significant induction of lactate dehydrogenase (LDH)activity was observed. The increase in glutamate dehydrogenase (GDH) and aspartate aminotransferase (Asp-AT) activities in the liver of aestivating P. dolloi suggests some energy may be obtained via increased aminoacid catabolism, leading to the generation of tricarboxylic acid (TCA) cycle intermediates. These findings indicate the importance of both carbohydrate and amino acid fuel stores during aestivation in aphylogenetically ancient, air-breathing fish.     

Metabolic characteristics of sea cucumber Apostichopus japonicus (Selenka) during aestivation

Metabolic characteristics of the sea cucumber Apostichopus japonicus (Selenka) during aestivation were studied in the laboratory. The effects of water temperature on oxygen consumption rate (OCR) and ammonia-N excretion rate (AER) in A. japonicus were determined by the Winkler and Hypobromite methods, respectively. Mature (large, 148.5 ± 15.4 g, medium 69.3 ± 6.9 g) and immature (small, 21.2 ± 4.7 g) individuals aestivated at water temperatures of 20 and 25 °C, respectively. The metabolic characteristics of mature individuals were different from immature individuals during this period. The OCR of mature sea cucumbers peaked at 20 °C, and then dropped significantly at higher temperatures, whereas the OCR of the immature animals continued to increase slightly, even beyond the aestivation temperature. The AER of mature individuals peaked at 20 °C, while that of the immature animals peaked at 25 °C. The relationships between dry weight (DW) and absolute oxygen consumption (R) and absolute ammonia-N excretion (N) could be described by the regression equation R or N = aW^b. With the exception of 15 °C, the O / N ratios (calculated in atomic equivalents) of large size sea cucumbers was close to 20 across the temperatures used in this study, indicating that their energy source was a combination of lipid and protein. On the other hand, apart from small individuals maintained at 10 °C, the O / N ratios of the medium and small sea cucumbers were close to 10, indicating that protein was their major energy source. The O / N ratios in all size groups remained unchanged after aestivation was initiated.