Postprandial Oxygen Consumption Research Articles

Application of a stoichiometric bioenergetic approach and whole-body protein synthesis to the nutritional assessment of juvenile Thenus australiensis

The present study successfully combined a stoichiometric bioenergetic approach with an endpoint stochastic model to simultaneously determine specific dynamic action, metabolic substrate use and whole-body protein synthesis in juvenile slipper lobster Thenus australiensis. Juvenile lobsters were fasted for 48 h to investigate routine metabolism before receiving a single meal of formulated feed containing 1% 15N-labeled Spirulina. Postprandial oxygen consumption rate, dissolved inorganic carbon, and total nitrogen excretion returned to the pre-feeding level within 24 h. The rate of whole-body protein synthesis was 0.76 ± 0.15 mg CP g−1 day−1, with a significant reduction from 24 to 48 h post-feeding. The postprandial increase in whole-body protein synthesis accounted for 13–19% of total oxygen uptake. Protein was the primary energy substrate for 48 h fasted (45% oxygen consumption) and post-feeding lobster (44%), suggesting that dietary protein was not efficiently used for growth. The secondary energy substrate differed between carbohydrates in 48 h fasted and lipids in post-feeding lobsters. The present study recommends integrating protein synthesis into protein requirement experiments of marine ectotherms to acquire a more comprehensive picture of protein and energy metabolism and nutritional physiology crucial for formulating cost-effective aquafeeds.

Cardamom (Elettaria cardamomum (L.) Maton) Seeds Intake Increases Energy Expenditure and Reduces Fat Mass in Mice by Modulating Neural Circuits That Regulate Adipose Tissue Lipolysis and Mitochondrial Oxidative Metabolism in Liver and Skeletal Muscle.

Cardamom seed (Elettaria cardamomum (L.) Maton; EC) is consumed in several countries worldwide and is considered a nutraceutical spice since it exerts antioxidant, anti-inflammatory, and metabolic activities. In obese individuals, EC intake also favors weight loss. However, the mechanism for these effects has not been studied. Here, we identified that EC modulates the neuroendocrine axis that regulates food intake, body weight, mitochondrial activity, and energy expenditure in mice. We fed C57BL/6 mice with diets containing 3%, 6%, or 12% EC or a control diet for 14 weeks. Mice fed the EC-containing diets gained less weight than control, despite slightly higher food intake. The lower final weight of EC-fed mice was due to lesser fat content but increased lean mass than control. EC intake increased lipolysis in subcutaneous adipose tissue, and reduced adipocyte size in subcutaneous, visceral, and brown adipose tissues. EC intake also prevented lipid droplet accumulation and increased mitochondrial content in skeletal muscle and liver. Accordingly, fasting and postprandial oxygen consumption, as well as fasting fat oxidation and postprandial glucose utilization were higher in mice fed with EC than in control. EC intake reduced proopiomelanocortin (POMC) mRNA content in the hypothalamic arcuate nucleus, without an impact on neuropeptide Y (NPY) mRNA. These neuropeptides control food intake but also influence the hypothalamic-pituitary-thyroid (HPT) and hypothalamic-pituitary-adrenal (HPA) axes. Thyrotropin-releasing hormone (TRH) mRNA expression in the hypothalamic paraventricular nucleus (PVN) and circulating triiodothyronine (T3) were lower in EC-fed mice than in control. This effect was linked with decreased circulating corticosterone and weight of adrenal glands. Our results indicate that EC modulates appetite, increases lipolysis in adipose tissue and mitochondrial oxidative metabolism in liver and skeletal muscle, leading to increased energy expenditure and lower body fat mass. These metabolic effects were ascribable to the modulation of the HPT and HPA axes. LC-MS profiling of EC found 11 phenolic compounds among which protocatechuic acid (23.8%), caffeic acid (21.06%) and syringic acid (29.25%) were the most abundant, while GC-MS profiling showed 16 terpenoids among which costunolide (68.11%), ambrial (5.3%) and cis-α-terpineol (7.99%) were identified. Extrapolation of mice-to-human EC intake was performed using the body surface area normalization equation which gave a conversion equivalent daily human intake dose of 76.9-308.4 mg bioactives for an adult of 60 kg that can be obtained from 14.5-58.3 g of cardamom seeds (18.5-74.2 g cardamom pods). These results support further exploration of EC as a coadjuvant in clinical practice.

Interactive effects of food deprivation state and hypoxia on the respiratory responses of postprandial rock crabs, Cancer irroratus.

Under the background of climate change, increasing attention has focused on the effects of ocean deoxygenation on marine organisms. However, few studies address the effects of different food deprivation states on hypoxia tolerance. We therefore investigated the metabolic responses of the Atlantic rock crab, Cancer irroratus (starved 28-35 days, fasted 3-5 days and recently fed). Starved-crab exhibited the lowest critical oxygen saturation (Scrit), while fed-crab had the highest Scrit. The fed-crab maintained an elevated postprandial oxygen consumption (MO2) even below the Scrit of fasted-crab indicating reserved aerobic scopes for critical activities in severe hypoxia. Following feeding, hypoxia (50% and 20% oxygen saturation, SO2) retarded the specific dynamic action resulting in lower peak MO2 and longer duration. The starved-crab exhibited a lower peak MO2, prolonged duration and higher energy expenditure than fasted-crab after feeding. The decline in arterial PO2 was most pronounced below the Scrit for both fasted- and starved-crab. The higher hemocyanin concentration ([Hc]) of fasted-crab (than starved-crab) suggested they had improved oxygen transport capacity, but hypoxia did not increase [Hc] during the 72-h experiment. Following feeding, the fasted-crab significantly increased L-lactate concentration ([L-lactate]) in 20% SO2, which was not observed in starved-crab. These results suggest starvation may trigger a cross-tolerance to hypoxia. Because crabs can undergo long periods of food deprivation in their natural environment, future studies should consider how this may affect their ability to deal with environmental perturbations.

Effects of food deprivation state on feeding behavior and gastric evacuation of rock crabs, Cancer irroratus, during hypoxia

ABSTRACT Climate change and anthropological activities have led to an expansion of hypoxia into the natural habitat of Cancer irroratus. In this study, we examined the effects of hypoxia and food deprivation state on food intake and subsequent gastric processing. Three different techniques were used to measure food intake. The gravimetric analysis of dry food pellets was the most accurate method. In severe hypoxia (20% oxygen), rock crabs reduced food intake, and more crabs refused to eat. Compared with fasted crabs, more starved crabs tended to eat in severe hypoxia. Subsequently, prolonged gastric emptying times paralleled the previously measured postprandial oxygen consumption in hypoxia. Starved crabs also exhibited slightly longer transit times for digesta compared with fasted crabs. These results suggest that although a trade-off may occur in starved rock crabs between the need to procure nutrients and deal with hypoxic stress, impaired digestive processing may still deleteriously affect these animals.

Effect of meal size on the postprandial metabolic response in Chinese giant salamander Andrias davidianus larvae

The digestive physiological characteristics of Chinese giant salamander Andrias davidianus have not been reported in the existing literature, and improving our knowledge in this area could help in the artificial culture of the species. The effect of meal size on the specific dynamic action (SDA) of A. davidianus larvae was assessed in this study at a water temperature of 20°C. The Chinese giant salamander was fed by test diets at meal sizes of 0.5, 1, 2, 4, 8 and 12% of its body mass (4.41 ± 0.07 g), and the postprandial oxygen consumption rate (MO2) was measured at 2 h intervals until the rate returned to its preprandial level. Peak MO2 (MO2peak) increased with meal size but levelled off at larger meal sizes within the studied range (8-12% body mass). The factorial metabolic scope increased from 1.27 to 2.11 when meal size increased from 0.5 to 12%. Time to reach MO2peak was not affected by the relative meal size. The SDA duration increased from 8.89 to 47.33 h as the relative meal size increased from 0.5 to 12%. The amount of energy expended during SDA increased linearly with increasing meal size (R2 = 0.842, p < 0.001, n = 60). There was no significant difference in the SDA coefficient among the different relative meal size groups. These data suggest that (1) A. davidianus larvae increase their energy demands during digestion by prolonging the SDA duration rather than increasing the MO2peak as meal size increases, and (2) A. davidianus showed a smaller factorial metabolic scope in the process of digesting large meal sizes, which may be related to the limited MO2peak of the species.

Effect of water salinity on the oxidative system of juveniles of the North Atlantic white shrimp Litopenaeus setiferus reared in biofloc technology

AbstractThis study evaluated the effect of biofloc technology (BFT) at 3 (lsBFT) and 35 (hsBFT) practice salinity units (psu) on the zootechnical performance, oxygen consumption, antioxidant activity, and oxidative damage of Litopenaeus setiferus juveniles reared in outdoor tanks. After 90 days, no significant differences were observed in terms of survival (p > .05). The final weight as well as wet weight gain, final biomass, and feeding conversion ratio (FCR) showed higher values for shrimp reared with hsBFT than those reared with lsBFT (p < .05). Compared to that for the hsBFT treatment, high oxygen consumption (VO2) was observed for the lsBFT treatment under fasting and postprandial conditions (p < .05). The activity of the enzymes catalase, superoxide dismutase, and glutathione‐S‐transferase from shrimp muscle did not show significant differences between the treatments (p > .05). Regarding the lipid peroxidation (LPO) and oxidized protein (PO) in muscle samples, no significant differences were observed in LPO, whereas the PO was significantly higher for the lsBFT treatment (p < .05), which was related to higher fasting and postprandial oxygen consumption of the juveniles (p < .05). The adaptation of L. setiferus juveniles reared in BFT at low salinity is relatively weak because of their low growth and excessive oxygen consumption and the oxidative damage (PO) produced.

A Single Dose of Goji Berries Does Not Affect Postprandial Energy Expenditure and Substrate Oxidation in Healthy, Overweight Men.

Background and Aim Increasing energy expenditure is an effective strategy for the prevention of obesity. In this respect, Lycium barbarum (goji berry) is of interest, as it has been shown to increase postprandial oxygen consumption. Although this suggests that energy expenditure was also increased, energy expenditure and substrate oxidation can only be assessed accurately when both oxygen consumption and carbon dioxide production are measured. We therefore investigated the effects of a single dose of Lycium barbarum fruit on postprandial energy expenditure and substrate oxidation in a randomized, double-blind crossover trial. In addition, markers of lipid and glucose metabolism were measured. Methods Seventeen healthy, overweight men received in a random order a meal containing 25 grams of dried Lycium barbarum fruit or a control meal matched for caloric content and macronutrient composition. Energy expenditure and the respiratory quotient were determined using indirect calorimetry before and up to 4 hours after meal intake. Blood was sampled before and after meal intake at regular intervals for analyses of plasma glucose, serum triacylglycerol, and free fatty acid concentrations. Results Energy expenditure significantly increased after the Lycium barbarum and control meal, but no differences were found between the meals (p=0.217). Postprandial changes in respiratory quotient (p=0.719) and concentrations of glucose (p=0.663), triacylglycerol (p=0.391), and free fatty acids (p=0.287) were also not affected by Lycium barbarum intake. Conclusions A single dose of Lycium barbarum does not affect postprandial energy expenditure, substrate oxidation, and markers for lipid and glucose metabolism in healthy, overweight men.

Feeding in Eptatretus cirrhatus: effects on metabolism, gut structure and digestive processes, and the influence of post-prandial dissolved oxygen availability

Hagfishes are characterised by feeding behaviours that may include long intervals between meals, and a hypoxic feeding environment inside decaying carrion. The effects of feeding on metabolism (oxygen consumption rate), gut mass and morphology (gut somatic index, gut epithelium mucosal thickness), and digestive function (maltase and peptidase activity) were examined in the New Zealand hagfish, Eptatretus cirrhatus. The influence of post-prandial hypoxia on oxygen consumption rate was also investigated to replicate the immersive feeding environment. Fed hagfish displayed a 1.9-fold increase in peak oxygen consumption relative to sham controls. This elevation in post-prandial oxygen consumption continued for 72 h, during which the energy cost of digesting the meal (specific dynamic action; SDA) was 2.1 kJ. Oxygen consumption rate increased when the post-prandial environment was hypoxic, a response suggesting a lack of hypoxia tolerance in this species. Feeding did not alter gut somatic index (percentage of digesta-free gut mass to whole body mass), but there was an increase in the mucosal thickness of the gut epithelium. Maltase activity in the gut was unchanged by feeding, but the activity of gut peptidases was increased significantly, consistent with a protein-based diet. These data indicate that some postprandial responses of New Zealand hagfish are similar in nature to those seen in other animals, but this species does not exhibit the extreme post-prandial physiological and biochemical changes that are observed in other intermittently-feeding vertebrates.

The effects of meal size on postprandial metabolic response and post-exercise metabolic recovery process in juvenile black carp (Mylopharyngodon piceus)

ABSTRACTThe effects of meal size on the postprandial metabolic response and of digestion on the post-exercise metabolic recovery process were investigated in juvenile black carp (Mylopharyngodon piceus) . Experimental fish were forcedly fed with compound feed (meal sizes: 0.5%, 1% and 2% body weight). Then, the postprandial oxygen consumption rate and excess post-exercise oxygen consumption (EPOC) of the experimental fish were measured. Both the duration and the peak of oxygen consumption rate (PMR) increased with increasing meal size. The peak post-exercise metabolic rate of digesting fish were significantly higher, whereas EPOC magnitude and its duration were significantly smaller or (shorter) than those in the fasting fish. It is suggested that (1) this fish fulfills the increased energy demand during the digestive process by increasing PMR and by prolonging SDA duration with increasing meal size and (2) digesting fish might decrease their anaerobic exhaustive activity but increase the post-exercise recovery capacity.

Post-prandial physiology and intestinal morphology of the Pacific hagfish (Eptatretus stoutii).

Hagfishes are unique to the vertebrate lineage in that they acquire dissolved nutrients across multiple epithelia including the intestine, gill, and skin. This feat has been attributed to their immersive feeding behavior that likely simultaneously provides benefits (nutrient rich) and potentially adverse (hypercapnia, hypoxia, high environmental ammonia) physiological effects. Examinations have been conducted of the ex vivo transport capabilities of specific nutrients as well as in vivo effects of the hypothesized feeding environments, yet the physiological effects of feeding itself have never been elucidated. We examined the post-prandial physiology of Pacific hagfish (Eptatretus stoutii), identifying changes in oxygen consumption, acid-base balance, ammonia waste excretion, and intestinal morphology following feeding in captivity. Following voluntary feeding, post-prandial oxygen consumption was significantly elevated (1868 ± 272µmolkg-1h-1) 8h following feeding when compared to control resting metabolic oxygen consumption (642 ± 51µmolkg-1h-1) and resulted in a factorial metabolic scope of 2.92. Changes in acid-base status were not observed following feeding in either the excreted components or the caudal blood samples; however, a significant alkalosis was observed 8h post-feeding in the major intestinal blood vein. Significant increases (16-fold) in ammonia excretion were recorded in 36h post-fed hagfish. Finally, significant post-prandial increases in intestinal mucosal thickness and microvilli length were observed, with mucosal thickness remaining significantly increased throughout 36h and the microvilli length returning to fasted lengths by 36h. These results demonstrate the post-feeding physiology of the earliest diverging extant craniate and identify correlations between physiology and hindgut morphology 8h following feeding.

Effect of some common West African farm-made feeds on the oxygen consumption and ammonia excretion rates of Nile tilapia, Oreochromis niloticus

The effects of two common West African farm-made feeds on postprandial metabolism were assessed in adult Nile tilapia (Oreochromis niloticus) by quantifying the oxygen consumption rates (MO2) and total ammonia-nitrogen (TAN) excretion over a 24-h period. Measurements followed the ingestion of a single meal of a fishmeal-based control diet and two diets containing 30% copra (CM) or palm kernel meal (PKM) inclusions by groups of 15 adult O. niloticus per tank. The mean net MO2 (postprandial oxygen consumption corrected for routine metabolic rate) during digestion for the different tilapia groups varied narrowly between 112.2 ± 9.9 and 129.9 ± 20.4 mg O2 kg−1 h−1 with the fish fed the CM diet recording a significantly lower (p = 0.04) net MO2 response relative to the other two diets. Net TAN excretion rates of the different dietary groups varied between 3.4 ± 1.4 and 4.4 ± 1.6 mg TAN kg−1 h−1. Under the standardized experimental conditions, copra and PKMs appeared to be promising candidates as partial replacements to fishmeal in tilapia diets as far as rates of oxygen consumption and ammonia-nitrogen excretion are concerned.

The effect of protein and lipid level on the specific dynamic action and post-prandial nitrogen excretion in subadult of white shrimp Litopenaeus vannamei

The study aimed to evaluate the effect of 4 levels of dietary protein (20, 30, 40 and 50%) and lipids (2, 4, 8 and 16%) on the magnitude and duration of specific dynamic action (SDA) and postprandial nitrogen excretion in the subadult white shrimp Litopenaeus vannamei using computer-controlled metabolic chambers (continuous-flow respirometer). We determined the oxygen consumption rate at 1 h intervals until the postprandial oxygen consumption rate returned to the pre-feeding level. Shrimp fed all the diets had significantly higher respiration rates after feeding due to the SDA. Oxygen consumption, the SDA coefficient and the SDA magnitude increased notably with increasing dietary protein content. Shrimp fed the 20% protein diet had the lowest levels of pre- and post-feeding respiration and the smallest SDA. A significant change in the SDA coefficient relative to each lipid level was not demonstrable. Additionally, nitrogenous excretion increased with an increase of dietary protein but not with an increase of lipid level. By estimating the SDA of subadults, the response to standard metabolic rate (SMR) was lower than that reported for juveniles and postlarva white shrimp

Embryonic hypoxia programmes postprandial cardiovascular function in adult common snapping turtles (Chelydra serpentina).

Reduced oxygen availability (hypoxia) is a potent stressor during embryonic development, altering the trajectory of trait maturation and organismal phenotype. We previously documented that chronic embryonic hypoxia has a lasting impact on the metabolic response to feeding in juvenile snapping turtles (Chelydra serpentina). Turtles exposed to hypoxia as embryos [10% O2 (H10)] exhibited an earlier and increased peak postprandial oxygen consumption rate, compared with control turtles [21% O2 (N21)]. In the current study, we measured central blood flow patterns to determine whether the elevated postprandial metabolic response in H10 turtles is linked to lasting impacts on convective transport. Five years after hatching, turtles were instrumented to quantify systemic ([Formula: see text]) and pulmonary ([Formula: see text]) blood flows and heart rate (fH) before and after a ∼5% body mass meal. In adult N21 and H10 turtles, fH was increased significantly by feeding. Although total stroke volume (VS,tot) remained at fasted values, this tachycardia contributed to an elevation in total cardiac output ([Formula: see text]). However, there was a postprandial reduction in a net left-right (L-R) shunt in N21 snapping turtles only. Relative to N21 turtles, H10 animals exhibited higher [Formula: see text] due to increased blood flow through the right systemic outflow vessels of the heart. This effect of hypoxic embryonic development, reducing a net L-R cardiac shunt, may support the increased postprandial metabolic rate we previously reported in H10 turtles, and is further demonstration of adult reptile cardiovascular physiology being programmed by embryonic hypoxia.

The effect of temperature on postprandial metabolism of yellowfin tuna (Thunnus albacares)

Specific dynamic action (SDA), the increase in metabolic expenditure associated with consumption of a meal, represents a substantial portion of fish energy budgets and is highly influenced by ambient temperature. The effect of temperature on SDA has not been studied in yellowfin tuna (Thunnus albacares, Bonnaterre 1788), an active pelagic predator that occupies temperate and subtropical waters. The energetic cost and duration of SDA were calculated by comparing routine and post-prandial oxygen consumption rates. Mean routine metabolic rates in yellowfin tuna increased with temperature, from 136mgO2kg−1h−1 at 20°C to 211mgO2kg−1h at 24°C. The mean duration of SDA decreased from 40.2h at 20°C to 33.1h at 24°C, while mean SDA coefficient, the percentage of energy in a meal that is consumed during digestion, increased from 5.9% at 20°C to 12.7% at 24°C. Digestion in yellowfin tuna is faster at a higher temperature but requires additional oxidative energy. Enhanced characterization of the role of temperature in SDA of yellowfin tuna deepens our understanding of tuna physiology and can help improve management of aquaculture and fisheries.

Oxygen uptake in Pacific salmon Oncorhynchus spp.: when ecology and physiology meet.

Over the past several decades, a substantial amount of research has examined how cardiorespiratory physiology supports the diverse activities performed throughout the life cycle of Pacific salmon, genus Oncorhynchus. Pioneering experiments emphasized the importance of aerobic scope in setting the functional thermal tolerance for activity in fishes. Variation in routine metabolism can have important performance and fitness consequences as it is related to dominance, aggression, boldness, territoriality, growth rate, postprandial oxygen consumption, life history, season, time of day, availability of shelter and social interactions. Wild fishes must perform many activities simultaneously (e.g. swim, obtain prey, avoid predators, compete, digest and reproduce) and oxygen delivery is allocated among competing organ systems according to the capacity of the heart to deliver blood. For example, salmonids that are simultaneously swimming and digesting trade-off maximum swimming performance in order to support the oxygen demands of digestion. As adult Pacific salmonids cease feeding in the ocean prior to their home migration, endogenous energy reserves and cardiac capacity are primarily partitioned among the demands for swimming upriver, sexual maturation and spawning behaviours. Furthermore, the upriver spawning migration is under strong selection pressure, given that Pacific salmonids are semelparous (single opportunity to spawn). Consequently, these fishes optimize energy expenditures in a number of ways: strong homing, precise migration timing, choosing forward-assist current paths and exploiting the boundary layer to avoid the strong currents in the middle of the river, using energetically efficient swimming speeds, and recovering rapidly from anaerobic swimming. Upon arrival at the spawning ground, remaining energy can be strategically allocated to the various spawning behaviours. Strong fidelity to natal streams has resulted in reproductively isolated populations that appear to be locally adapted physiologically to their specific environmental conditions. Populations with more challenging migrations have enhanced cardiorespiratory performance. Pacific salmonids are able to maintain aerobic scope across the broad range of temperatures encountered historically during their migration; however, climate change-induced river warming has created lethal conditions for many populations, raising conservation concerns. Despite considerable research examining cardiorespiratory physiology in Pacific salmonids over the last 70 years, critical knowledge gaps are identified.

Thermic Effect of Food, Macronutrient Oxidation Rate and Satiety of Medium-chain Triglyceride

Objectives: The objective of this study was to evaluate the thermic effects, the macronutrient oxidation rates and the satiety of medium-chain triglycerides (MCT). Methods: The thermic effects of two meals containing MCT or long-chain triglycerides (LCT) were compared in ten healthy men (mean age 24.4 ± 2.9 years). Energy content of the meal was 30% of resting metabolic rate of each subject. Metabolic rate and macronutrient oxidation rate were measured before the meals and for 6 hours after the meals by indirect calorimetry. Satiety was estimated by using visual analogue scales (VAS) at 8 times (before the meal and for 6 hours after meal). Results: Total thermic effect of MCT meal (42.8 kcal, 8.0% of energy intake) was significantly higher than that (26.8 kcal, 5.1% of energy intake) of the LCT meal. Mean postprandial oxygen consumption was also significantly different between the two types of meals (MCT meal: 0.29 ± 0.35 L/min, LCT meal: 0.28 ± 0.27 L/min). There were no significant differences in total postprandial carbohydrate and fat oxidation rates between the two meals. However, from 30 to 120 minutes after consumption of meals, the fat oxidation rate of MCT meal was significantly higher than that of the LCT meal. Comparison of satiety values (hunger, fullness and appetite) between the two meals showed that MCT meal maintained satiety for a longer time than the LCT meal. Conclusions: This study showed the possibility that long-term substitution of MCT for LCT would produce weight loss if energy intake remained constant. Korean J Community Nutr 20(6): 468~478, 2015

A comparison of the cardiovascular responses to anemia in digesting Burmese pythons and American alligators

Burmese pythons (Python molurus) and American alligators (Alligator mississippiensis) utilize intermittent feeding strategies, with prolonged fasts punctuated by bouts of voracious feeding. Both species exhibit large increases in postprandial oxygen consumption (V̇O2). Presumably in response to increased O2 demand, P. molurus has been shown to exhibit postprandial cardiac hypertrophy (PCH) of up to 40%. By contrast, alligators exhibit no significant PCH. The “triggers” and universality (both within and between species) of this response therefore remain unclear. Notably, maximal V̇O2 in digesting Burmese pythons may exceed V̇O2 during maximal activity, whereas the opposite is true in alligators. We hypothesize that an O2 supply‐demand mismatch triggers PCH, which was tested in both species by halving hematocrit values (inducing anemia) and feeding animals large meals. Within 48 hours after feeding, normoxic and anemic pythons exhibited heart rates 78% and 126% higher, respectively, than fasted controls. While no PCH was found in fed normoxic animals, fed anemic animals exhibited 38% more massive hearts. Similar cardiovascular responses and hypertrophies occurred in fed anemic alligators. These findings support our hypothesis that an oxygen supply‐demand mismatch is the upstream stimulant of PCH, a phenomenon now known to exist across at least two taxa of reptiles. Funding provided by the Danish Research Council to TW and NSF grant IOS 0922756 to JWH. CES received support from an NSF GRF and a SICB FGST.

Effect of meal size on postprandial metabolic response and excess post-exercise oxygen consumption in juvenile rock carp (Procypris rabaudi)

To investigate the effect of meal size on postprandial metabolic response and excess post-exercise oxygen consumption(EPOC) in juvenile rock carp(Procypris rabaudi)[(13.05±0.17) g,n=44],experimental fish were lightly anaesthetized and force-fed with compound feed(meal sizes: 0%,0.5%,1% and 2% body weight) at(25 ±0.5)℃.After diet offered,oxygen consumption rates at different intervals were measured.Variables of postprandial metabolic and EPOC responses were calculated.The results of present study showed that resting metabolic rates(RMR) were not significantly different among all groups.The postprandial metabolic rate first increased and then slowly decreased to pre-fed level.The time to peak metabolic rate and the energy expended on Specific dynamic action(SDA) in 0.5% and 1% meal size groups were lower than that of 2% meal size group(P0.05).The peak metabolic rates(PMR) and the SDA coefficients were not significantly different among 0.5%,1% and 2% meal size groups.Pre-exercise metabolic rate in feeding group was significantly higher than that of fasting group(P0.05).Peak post-exercise metabolic rate,metabolic rate increment and excess post-exercise oxygen consumption magnitude were not significantly different between feeding group and fasting group.The maximum metabolic rate(MMR) and MMR/RMR were significantly higher than PMR and PMR/RMR(P0.05).The fish fulfilled the increased energy demand during digestive process by means of prolonged SDA duration with the increase of meal size.EPOC was not influenced by feeding in the fish.

Effect of meal size on the specific dynamic action of the juvenile snakehead (Channa argus)

The effect of meal size on the specific dynamic action (SDA) of the juvenile snakehead (Channa argus) was assessed at 25°C. The fish were fed with test diets at meal sizes of 0.5, 1, 2, 3, 4, and 5% body mass and the postprandial oxygen consumption rate was determined at 1-h intervals until it returned to the pre-prandial level. The peak metabolic rate increased from 237.4 to 283.2mgO2kg−1h−1 as the relative meal size increased from 0.5% to 3% and leveled off at 4% and 5%. Factorial metabolic scope increased from 1.53 to 1.99 and SDA duration increased from 11.7 to 32.3h as the relative meal size increased from 0.5% to 5%. The relationship between SDA duration (D) and relative meal size (M) was described as: D=4.28M+10.62 (r2=0.752, P<0.05, n=50). The energy expended on SDA increased while the SDA coefficient decreased with increasing meal size. The results of the present study suggest that the snakehead may adopt different feeding strategies when taking in different amounts of food.

Specific dynamic action affects the hydrostatic pressure tolerance of the shallow-water spider crab Maja brachydactyla

The bathymetric distribution of marine benthic invertebrates is likely governed by a combination of ecological and physiological factors. The present study investigates oxygen consumption and heartbeat rate in response to attempted feeding at 1, 100 and 150 atm in the shallow-water spider crab, Maja brachydactyla, from temperate European waters. No significant difference was evident between the resting heartbeat rate of specimens at 1 or 100 atm, which were 56 and 65 bpm, respectively (Mann-Whitney, U = 5382.0; n = 95, 98; p = 0.079). However, at 150 atm the resting heartbeat rate was significantly higher than that observed for 100 atm at 108 bpm (Mann-Whitney, U = 49.0; n = 45, 98; p < 0.001). At 150 atm, feeding was never observed and coupled with the elevated resting heartbeat rate; it is suggested by 150 atm continued survival is unfeasible. At 1 and 100 atm, feeding instigated a distinct increase in heartbeat rate, which remained elevated for over 30 h. This increase peaked within 1 h at 1 atm. At 100 atm, this required 4 h and postprandial oxygen consumption was significantly higher than at 1 atm (Kruskal-Wallis, H = 85.036; df = 2; p < 0.001). Elevated hydrostatic pressure is hypothesized to extend the duration and the total metabolic energy devoted to specific dynamic action. The metabolic requirements of feeding under hyperbaric conditions may even reach such a critical demand that feeding is entirely inhibited.