Effect of meal size on excess post-exercise oxygen consumption in fishes with different locomotive and digestive performance

Effects of feeding on pre-exercise VO₂ and excess post-exercise oxygen consumption (EPOC) after exhaustive exercise were investigated in sedentary southern catfish, active herbivorous grass carp, omnivorous crucian carp, and sluggish omnivorous darkbarbel catfish to test whether feeding had different effects on EPOC and to compare EPOC in fishes with different ecological habits. For fasting fish, the pre-exercise and peak post-exercise VO₂ were higher and recovery rates were faster in crucian carp and grass carp compared to those of darkbarbel catfish and southern catfish. EPOC magnitudes of grass carp and southern catfish were significantly larger than those of crucian carp and darkbarbel catfish. Feeding had no significant effect on peak post-exercise VO₂, recovery rate, and EPOC magnitude in grass carp. Both the pre-exercise and peak post-exercise VO₂ increased with meal size, while the EPOC magnitude and duration decreased significantly in the larger meal size groups of crucian carp and southern catfish. In darkbarbel catfish, both the pre-exercise and peak post-exercise VO₂ increased with meal size, but the VO₂ increment elicited by exercise was larger in feeding groups compared with the fasting group. These results suggest that (1) the characteristics of the post-exercise VO₂ profile, such as peak post-exercise VO₂ and recovery rate, were closely related to the activity of fishes, whereas the EPOC magnitude was not and (2) the effects of feeding on EPOC were more closely related to the postprandial increase in VO₂.     

中华倒刺鲃幼鱼能量代谢特征个体差异及生态关联

为了探讨鱼类能量代谢特征个体变异及其生态关联, 以中华倒刺鲃(Spinibarbus sinensis)幼鱼为实验对象, 在25℃条件下测定44尾实验鱼的静止代谢率(Resting metabolic rate, RMR)、力竭运动后峰值代谢率(Peak metabolic rate, PMR)、力竭运动后过量耗氧(Excess post-exercise oxygen consumption, EPOC)、低氧胁迫后峰值代谢率PMR和低氧胁迫后过量耗氧(Excess post-hypoxia oxygen consumption, EPHOC)。研究发现, 中华倒刺鲃能量代谢特征参数存在较大个体差异, RMR、力竭运动后PMR、EPOC、低氧胁迫后PMR和EPHOC分别为193.62—460.33 [mg O₂/(kg·h)]、617.9—2165.02 [mg O₂/(kg·h)]、28.76—267.20 mg O₂/kg、484.3—1142.97 [mg O₂/(kg·h)]和30.27—211.88 mg O₂/kg。力竭运动后PMR(r=0.348, P=0.010)和低氧胁迫后PMR(r=0.449, P=0.002)与RMR间均呈显著正相关; EPOC与RMR间呈显著负相关(r=–0.426, P=0.004), 而EPHOC与RMR间的关系不显著(r=–0.292, P=0.054); 力竭运动后PMR与EPOC间(r=0.424, P=0.004)和低氧胁迫后PMR与EPHOC间(r=0.391, P=0.009)均呈显著正相关。力竭运动后PMR与低氧胁迫后PMR(r=0.673, P<0.001)和EPOC与EPHOC(r=0.526, P<0.001)在个体差异均显著正相关; 然而力竭运动后PMR和EPOC分别显著高于低氧胁迫后PMR与EPHOC(P<0.05)。研究表明: 维持代谢较高的中华倒刺鲃个体有助于其快速提升有氧功率输出以维持高的游泳运动能力; 而较低维持代谢个体具有相对较高的EPHOC有助于机体在极端环境条件下提升其低氧耐受能力。中华倒刺鲃能量特征的个体变异可能是经长期自然选择适应环境的结果。     

力竭追赶训练对两种鲤科鱼类呼吸循环系统参数和力竭运动后代谢特征的影响

为了考察力竭追赶训练对中华倒刺鲃(Spinibarbus sinensis)和岩原鲤(Procypris rabaudi)幼鱼呼吸循环系统和力竭运动后代谢特征的影响, 在(25±0.5)℃条件下, 将2种实验鱼各60尾 [体重分别为(28.36±0.08) g和(19.53±0.13) g]随机等分成对照组和训练组, 训练组进行1次/d共21d的力竭追赶训练。随后测定各组实验鱼的心脏和鳃指数、血液指标以及力竭运动后过量耗氧(Excess post-exercise oxygen consumption, EPOC)。结果发现: 2种鱼心脏指数、鳃指数、血红蛋白含量和红细胞数目在各自对照组和训练组之间都没有显著性差异; 岩原鲤对照组的鳃指数显著低于中华倒刺鲃对照组(P<0.05), 但心脏指数、血红蛋白含量和红细胞数目与中华倒刺鲃对照组无显著性差异。中华倒刺鲃训练组的运动前代谢率、运动代谢峰值、峰值比率、代谢恢复速率与其对照组没有显著差异, 但运动后恢复时间和过量耗氧显著大于对照组(P<0.05); 岩原鲤训练组的运动前代谢率显著低于其对照组(P<0.05), 但运动代谢峰值、峰值比率、运动后恢复时间、过量耗氧、代谢恢复速率与其对照组没有显著性差异。岩原鲤对照组的运动前代谢率、运动代谢峰值、过量耗氧和代谢恢复速率分别显著低于中华倒刺鲃对照组(P<0.05), 但峰值比率和运动后恢复时间与中华倒刺鲃对照组无显著性差异。研究表明: (1)力竭追赶训练对中华倒刺鲃和岩原鲤幼鱼的呼吸和循环系统参数没有产生显著性影响; (2)力竭追赶训练显著提高了中华倒刺鲃幼鱼的无氧代谢能力; (3)中华倒刺鲃幼鱼力竭运动前后代谢率显著高于岩原鲤幼鱼, 这可能与其较为活跃的习性有关。     

Effects of body lipid content on the resting metabolic rate and postprandial metabolic response in the southern catfish Silurus meridionalis

We assessed the effects of body lipid content on the resting metabolic rate and specific dynamic action (SDA) of the southern catfish Silurus meridionalis. Obese and lean fish were obtained by feeding the fish with two different feeds at 27.5 °C for 4 weeks prior to the experiment. The fish were fed with experimental diets with a meal size of 4% by body mass. A continuous-flow respirometer was used to determine the oxygen consumption rate at 2-h intervals until the postprandial oxygen consumption rate had returned to the preprandial level. The body lipid content of the obese fish was significantly greater than that of the lean fish. The metabolic parameters evaluated (resting metabolic rate, peak metabolic rate (R_peak), factorial ratio, time to peak, duration, energy expended on SDA (SDA_E), or SDA coefficient) were not significantly affected by body fat content in terms of the whole-body or mass-specific values. Increased body fat content did not decrease the resting metabolic rate in the southern catfish, which might be due to the higher levels of highly unsaturated fatty acids in these fish. The results also suggest that the body composition does not appear to affect the SDA response.     

Effect of feeding and fasting on excess post-exercise oxygen consumption in juvenile southern catfish (Silurus meridionalis Chen)

The impact of feeding (fed to satiation, 13.85% body mass) on excess post-exercise oxygen consumption (EPOC, chasing for 2.5 min) was investigated in juvenile southern catfish (Silurus meridionalis Chen) (38.62-57.55 g) at 25. Cutlets of freshly killed loach species without viscera, head and tail were used as the test meal, and oxygen consumption (VO(2)) was adjusted to a standard body mass of 1 kg using a mass exponent of 0.75. Resting VO(2) increased significantly above fasting levels (49.89 versus 148.25 mg O(2) h(-)(1)) in 12 h postprandial catfish. VO(2) and ventilation frequency (V(f)) both increased immediately after exhaustive exercise and slowly returned to pre-exercise values in all experimental groups. The times taken for post-exercise VO(2) to return to the pre-exercise value were 20, 25 and 30 min in 12 h, 60 h and 120 h postprandial catfish, respectively. Peak VO(2) levels were 257.36+/-6.06, 219.32+/-6.32 and 200.91+/-5.50 mg O(2) h(-1) in 12 h, 60 h and 120 h postprandial catfish and EPOC values were 13.85+/-4.50, 27.24+/-3.15 and 41.91+/-3.02 mg O(2) in 12 h, 60 h and 120 h postprandial southern catfish, respectively. There were significant differences in both EPOC and peak VO(2) during the post-exercise recovery process among three experimental groups (p<0.05). These results showed that: (1) neither digestive nor exhaustive exercise could elicit maximal VO(2) in southern catfish, (2) both the digestive process and exercise (also the post-exercise recovery process) were curtailed under postprandial exercise, (3) the change of V(f) was smaller than that of VO(2) during the exhaustive exercise recovery process, (4) for a similar increment in VO(2), the change in V(f) was larger during the post-exercise process than during the digestive process.     

Roles of lactate and catecholamines in the energetics of brief locomotion in an ectothermic vertebrate

We have investigated the magnitude and duration of excess post-exercise oxygen consumption (EPOC) in a lizard following a single bout of vigorous exercise of 5-60 s, common activity durations for many ectothermic vertebrates. Desert iguanas (Dipsosaurus dorsalis) were run for 5 s, 15 s, 30 s, or 60 s. Oxygen consumption (VO2) increased from 0.16 ml O2 g(-1) h(-1) at rest to 1.3-1.6 ml O2 g(-1) h(-1) during 5-60 s of running. EPOC duration increased with activity duration, ranging from 35-63 min. EPOC volume, the excess oxygen consumed post-exercise, doubled from 0.13 ml O2 g(-1) following 5 s of activity to 0.25 ml O2 g(-1) after 60 s. EPOC represented 91-98% of the total metabolic expense of the activity. EPOC durations were always shorter than the period required for lactate removal, illustrating that these two processes are not causally related. Alpha- and beta-adrenergic receptor blockade by phentolamine and propranolol had no effect on resting VO2 but depressed excess post-exercise oxygen consumption volumes 2540%. The extent of catechol stimulation post-exercise may be motivation or stimulus dependent. The data indicate that metabolic elevations post-exercise represent the majority of activity costs in lizards. The study suggests that EPOC of ectothermic vertebrates is sensitive to exercise duration and catecholamine release post-activity, even when activity periods are less than 60 s in duration.     

Effect of activity duration on recovery and metabolic costs in the desert iguana (Dipsosaurus dorsalis).

The majority of elevated O(2) consumption associated with short and vigorous activity occurs during recovery, thus an assessment of associated metabolic costs should also examine the excess post-exercise oxygen consumption (EPOC). This study examined O(2) uptake during exercise, EPOC and distance traveled during 5-, 15-, 60- and 300-s sprints at maximal treadmill intensity in Dipsosaurus (N=10; 74.3+/-2.1 g). EPOC (0.08, 0.14, 0.23 and 0.18 ml O(2) g(-1), respectively) was large (80-99% of total elevated O(2) consumption) and increased significantly between 5 and 60 s. The cost of activity (C(act); ml O(2) g(-1) x km(-1)), intended to reflect the total net costs associated with the activity, was calculated as the total elevated O(2) consumption per unit distance traveled. C(act) decreased with activity duration due to proportionally larger increases in distance traveled relative to EPOC volume, and is predicted by the equation C(act)=14.7 x activity duration (s)(-0.24). The inclusion of EPOC costs provides an ecologically relevant estimate of the total metabolic cost of locomotor activity. C(act) exceeds standard transport costs at all durations examined due to the addition of obligate recovery costs. The differences are large enough to impact energy budget analyses for ectotherms.     

Effect of meal size on postprandial metabolic response in Chinese catfish (Silurus asotus Linnaeus)

The effect of relative meal size (0.5–24% body mass) on specific dynamic action (SDA) was assessed in Chinese catfish (Silurus asotus Linnaeus) (30.90±1.30 g) at 25.0°C; the cutlets of freshly killed loach without viscera, head and tail were used as a test meal. There was no significant difference in either SDA duration or peak oxygen consumption (VO₂) among low meal size ranges. But both increased linearly as meal size increased from 2 to 24% without reaching a plateau. Factorial metabolic scope was 5.92 in fish fed with 24% body mass, the highest documented feeding metabolic scope value in fish till now. The Peak VO₂ of satiated meal size groups (175.85±10.55 mg O₂ h⁻¹) was above 80% of maximum metabolic rate during locomotion recovery process (215.48±7.07 mg O₂ h⁻¹). The relationship between energy expended on SDA (E) and energy ingested (I) was described as: E=0.0000432I ²+0.140I+2.12. The lowest value of SDA coefficient appeared at 2% body mass group.     

有氧运动训练和摄食对中华倒刺鲃幼鱼力竭运动后代谢特征的影响

为了探讨有氧运动训练和摄食对中华倒刺鲃（Spinibarbus sinensis）幼鱼力竭运动后代谢特征的影响,在（25±0.5）℃条件下,将120尾实验鱼[体重（21.35±0.05）g,体长（10.21±0.03）cm]随机分成4组,即:对照组、1、2和4 BL/s（体长/秒,body length/s）训练组,分别放置于不同流速下处理8周。随后测定各实验组心脏和鳃指数以及禁食或摄食（轻度麻醉灌喂体重1.5%的饵料）状态下的力竭运动后过量耗氧。结果发现:4 BL/s训练组的心脏和鳃指数都显著高于其他实验组（P < 0.05）;无论摄食与否,3个训练组运动前代谢率都显著高于对照组（P=0.001）,而各实验组过量耗氧均没有显著差异;在禁食状态下,仅4 BL/s训练组的运动代谢峰值和代谢率增量显著高于对照组,而在摄食状态下,3个训练组的运动代谢峰值和代谢率增量均显著高于对照组（P < 0.005）。与禁食组相比,摄食导致各处理组的运动前代谢率显著上升（P < 0.001）,但对运动代谢峰值没有显著影响;另外,摄食对照组代谢率增量和力竭运动后过量耗氧显著低于禁食对照组（P < 0.05）。研究表明:（1）有氧运动训练显著提高了中华倒刺鲃幼鱼的有氧代谢能力,这可能与其呼吸和循环系统功能的改善有关;（2）力竭运动能够诱导出中华倒刺鲃幼鱼的最大有氧代谢率;（3）摄食削弱了中华倒刺鲃幼鱼无氧代谢能力。     

Metabolic response of bluegill to exercise at low water temperature: implications for angling conservation

The metabolic response of fish to exercise is highly dependent on environmental factors such as temperature. In addition to natural challenges that force exercise (foraging, avoiding predators, etc.), sportfish species are also subjected to exercise when they are hooked by anglers, leading to metabolic energy costs that may impact fitness. While several studies have examined the physiological response of fish to capture in warm conditions, little work has examined this response under cold winter conditions when fish are targeted by ice-anglers. To fill this gap, we examined the metabolic impacts of exercise duration and air exposure on bluegill, Lepomis macrochirus, at a temperature typical for ice angling. Thirty-two bluegill were subjected to a simulated angling session which included either a light (30 s) or exhaustive exercise procedure, followed by either 30 s or 4 min of air exposure. Fish were then assessed at 5 °C for the following metabolic metrics using intermittent-flow respirometry: standard metabolic rate (SMR), maximum metabolic rate (MMR), aerobic scope (AS), recovery time, and excess post-exercise oxygen consumption (EPOC). Fish exercised to exhaustion had higher EPOC compared to lightly exercised fish, however EPOC was not affected by air exposure time. No other metrics were impacted by air exposure or exercise duration. These results are directly applicable to physiological outcomes for fish captured by ice-anglers during the winter and suggest that both low temperatures and low durations of exercise serve to keep metabolic costs low for fish angled during the winter months.     

Intraspecific mass scaling of metabolic rates in grass carp (Ctenopharyngodon idellus)

We assessed the intraspecific mass scaling of standard metabolic rate (SMR), maximum metabolic rate (MMR), excess post-exercise oxygen consumption (EPOC), and erythrocyte size in grass carp (Ctenopharyngodon idellus), with body masses ranging from 4.0 to 459 g. SMR and MMR scaled with body mass with similar exponents, but neither exponent matched the expected value of 0.75 or 1, respectively. Erythrocyte size scaled with body mass with a very low exponent (0.090), suggests that while both cell number and cell size contribute to the increase in body mass, cell size plays a smaller role. The similar slopes of MMR and SMR in grass carp suggest a constant factorial aerobic scope (FAS) as the body grows. SMR was negatively correlated with FAS, indicating a tradeoff between SMR and FAS. Smaller fish recovered faster from the exhaustive exercises, and the scaling exponent of EPOC was 1.075, suggesting a nearly isometric increase in anaerobic capacity. Our results provide support for the cell size model and suggest that variations of erythrocyte size may partly contribute to the intraspecific scaling of SMR. The scaling exponent of MMR was 0.863, suggesting that the metabolism of non-athletic fish species is less reliant on muscular energy expenditure, even during strenuous exercise.     

A three‐phase excess post‐exercise oxygen consumption in Atlantic salmon Salmo salar and its response to exercise training

The recovery of oxygen uptake to the standard metabolic rate (SMR) following exhaustive chasing exercise in Atlantic salmon Salmo salar parr occurred in three phases (rapid, plateau and slow). The initial recovery phase lasted 0·7 h and contributed 16% to the total excess post‐exercise oxygen consumption (EPOC). It was followed by a longer plateau phase that contributed 53% to the total EPOC. The slow recovery phase that completed recovery of SMR, which has not been reported previously, made a 31% contribution to the total EPOC. The plasticity of EPOC was demonstrated in exercise‐trained fish. Exercise training increased EPOC by 39% when compared with control fish (mean ± S.E., 877·7 ± 73·1 v . 629·2 ± 53·4 mg O₂ kg^?1, d.f. = 9, P <  0·05), with the duration of the plateau phase increasing by 38% (4·7 ± 0·58 v . 3·4 ± 0·16 h, d.f. = 9, P <  0·05) and the contribution of the slow phase to the total EPOC increasing by 80% (173·9 ± 23·9 v . 312·5 ± 50·4 mg O₂ kg^?1, d.f. = 9, P  < 0·05). As a result, the combination of the plateau and slow phases of exercise‐trained fish increased by 47% compared with control fish (756·6 ± 71·4 v . 513·6 ± 43·1 mg O₂ kg^?1; d.f. = 9, P  = 0·01). To substantiate the hypothesis that the plateau and slow recovery phase of EPOC was related to general metabolic recovery following exhaustive exercise, the time‐course for recovery of SMR was compared with previously published metabolite recovery profiles. The final phase of metabolic recovery was temporally associated with the final phases of gluconeogenesis, lactate oxidation and muscle intracellular pH regulation. Therefore, the plasticity of the latter phase of EPOC agreed with the known effects of exercise training in fishes.     

Specific dynamic action of ambystomatid salamanders and the effects of meal size, meal type, and body temperature

The past decade has witnessed a dramatic increase in studies of amphibian and reptile specific dynamic action (SDA). These studies have demonstrated that SDA, the summed energy expended on meal digestion and assimilation, is affected significantly by meal size, meal type, and body size and to some extent by body temperature. While much of this attention has been directed at anuran and reptile SDA, we investigated the effects of meal size, meal type, and body temperature on the postprandial metabolic responses and the SDA of the tiger salamander (Ambystoma tigrinum tigrinum). We also compared the SDA responses among six species of Ambystoma salamanders representing the breadth of Ambystoma phylogeny. Postprandial peaks in VO(2) and VO(2), duration of elevated metabolism, and SDA of tiger salamanders increased with the size of cricket meals (2.5%-12.5% of body mass). For A. tigrinum, as for other ectotherms, a doubling of meal size results in an approximate doubling of SDA, a function of equal increases in peak VO(2) and duration. For nine meal types of equivalent size (5% of body mass), the digestion of hard-bodied prey (crickets, superworms, mealworms, beetles) generated larger SDA responses than the digestion of soft-bodied prey (redworms, beetle larvae). Body temperature affected the profile of postprandial metabolism, increasing the peak and shortening the duration of the profile as body temperature increased. SDA was equivalent among three body temperatures (20 degrees, 25 degrees, and 30 degrees C) but decreased significantly at 15 degrees C. Comparatively, the postprandial metabolic responses and SDA of Ambystoma jeffersonianum, Ambystoma maculatum, Ambystoma opacum, Ambystoma talpoideum, Ambystoma texanum, and the conspecific Ambystoma tigrinum mavortium digesting cricket meals that were 5% of their body mass were similar (independent of body mass) to those of A. t. tigrinum. Among the six species, standard metabolic rate, peak postprandial VO(2), and SDA scaled with body mass with mass exponents of 0.72, 0.78, and 1.05, respectively.     

Effects of meal size,meal type,body temperature,and body size on the specific dynamic action of the marine toad,Bufo marinus

Specific dynamic action (SDA), the accumulated energy expended on all physiological processes associated with meal digestion, is strongly influenced by features of both the meal and the organism. We assessed the effects of meal size, meal type, body temperature, and body size on the postprandial metabolic response and calculated SDA of the marine toad, Bufo marinus. Peak postprandial rates of O(2) consumption (.V(O2)) and CO(2) production (.V(CO2)) and SDA increased with meal size (5%-20% of body mass). Postprandial metabolism was impacted by meal type; the digestion of hard-bodied superworms (Zophobas larva) and crickets was more costly than the digestion of soft-bodied earthworms and juvenile rats. An increase in body temperature (from 20 degrees to 35 degrees C) altered the postprandial metabolic profile, decreasing its duration and increasing its magnitude, but did not effect SDA, with the cost of meal digestion remaining constant across body temperatures. Allometric mass exponents were 0.69 for standard metabolic rate, 0.85 for peak postprandial .V(O2), and 1.02 for SDA; therefore, the factorial scope of peak postprandial .V(O2) increased with body mass. The mass of nutritive organs (stomach, liver, intestines, and kidneys) accounted for 38% and 20% of the variation in peak postprandial .V(O2) and SDA, respectively. Toads forced to exercise experienced 25-fold increases in .V(O2) much greater than the 5.5-fold increase experience during digestion. Controlling for meal size, meal type, and body temperature, the specific dynamic responses of B. marinus are similar to those of the congeneric Bufo alvarius, Bufo boreas, Bufo terrestris, and Bufo woodhouseii.     

Individual variation in metabolism and thermal tolerance in juvenile qingbo (Spinibarbus sinensis)

Studies of individual variation in the physiological performance of animals and their relationship with metabolism may provide insight into how selection influences diversity in phenotypic traits. Thus, the aims of the present study were to investigate variation in thermal tolerance and its relationship with individual metabolism in juvenile qingbo (Spinibarbus sinensis). To fulfill our goal, we first measured the resting metabolic rate (RMR), maximum metabolic rate (MMR), metabolic scope (MS, MMR–RMR) and excess post-exercise oxygen consumption (EPOC) of 40 fish at 25 °C. We then measured the critical thermal minimum (CT_min), lethal thermal minimum (LT_min), critical thermal maximum (CT_max), and lethal thermal maximum (LT_max) of 20 fish. Both MMR and MS were positively correlated with the metabolic recovery rate (MRR) (p = 0.001), indicating that high aerobic metabolic performance individuals possessed an advantage for the recovery of anaerobic metabolism. However, the negative correlation between EPOC and MRR (p = 0.017) indicated a slow recovery of the metabolism of high anaerobic metabolic capacity individuals. The RMR was positively correlated with CT_min and LT_min, whereas all of the metabolic rate parameters (RMR, MMR, and MS) were negatively correlated with CT_max and LT_max (p < 0.05), indicating that high aerobic metabolic performance individuals have a weakened thermal tolerance. These results suggested that there is a trade-off between aerobic metabolic performance and thermal tolerance.     

PFOS对中华倒刺鲃幼鱼爆发游泳及运动后代谢恢复的影响

为探究水体全氟辛烷磺酸(PFOS)污染对鱼类爆发游泳及其代谢恢复能力的影响, 将中华倒刺鲃幼鱼(Spinibarbus sinensis)暴露在不同浓度(0、0.32、0.8、2和5 mg/L)PFOS后, 测定PFOS暴露对其静止代谢率(RMR)、爆发游泳速度(U_burst)以及运动力竭后代谢恢复特征的影响。结果发现, 暴露浓度对实验鱼的U_burst和相对爆发游泳速度(rU_burst)均影响显著(P<0.05), 5 mg/L PFOS暴露导致U_burst和rU_burst分别下降了17.4%和10.8%, PFOS对rU_burst的影响表现出“非单调剂量效应”; 暴露浓度对实验鱼的RMR影响显著(P<0.05), 5 mg/L PFOS暴露导致RMR显著升高, 但PFOS对运动后代谢峰值(MMR)、代谢率增量(MS)、代谢变化倍率(F-MS)、力竭运动后过量氧耗(EPOC)无显著影响(P>0.05)。研究结果提示: PFOS污染改变实验鱼能量代谢水平的下限, 而对其代谢水平的上限无明显的限制性作用; PFOS污染将可能对鱼类捕食——逃避捕食者、穿越激流寻找适宜生境等生存关联的生命活动起到负面影响, 但对无氧代谢关联的代谢恢复能力无显著的生态毒理效应。     

Is peak postprandial oxygen consumption positively related to growth rate and resting oxygen consumption in a sedentary catfish Silurus meridionalis?

The resting oxygen consumption     , postprandial and post-exercise peak oxygen consumption     of 137 juvenile southern catfish Silurus meridionalis , weighing 18·5 ± 0·8 g (mean ± s . d .), were measured at 25° C to determine whether     is positively related to postprandial and post-exercise     in sedentary S. meridionalis . In addition, postprandial metabolic response [ i.e. the specific dynamic action (SDA)] after a satiating meal and the growth performance as a consequence of a 3 week feeding-growth trail were measured in 40 S. meridionalis , weighing 14·3 ± 0·2 g, at 25° C to determine whether postprandial     is positively related to growth rate. Postprandial     was positively correlated with     , while post-exercise     was not. Both postprandial     and post-exercise     were positively correlated with factorial and absolute scope. There was no significant correlation between the growth rate and postprandial     in S. meridionalis . It suggested that as a sit-and-wait forager with low     , low post-exercise     and high postprandial     , the expenditure of energy for maintenance in S. meridionalis may be more closely related to digestive processes than locomotor activities.     

Effect of meal size on postprandial metabolic response in southern catfish (Silurus meridionalis)

Effect of relative meal size (0.6-24%) on specific dynamic action (SDA) was assessed in southern catfish juveniles (48.2+/-3.2 g) at 27.5 degrees C. Cutlets of freshly killed loach species were used as test diet. Energy expended during SDA was linearly correlated with relative meal size (r=0.949, p<0.001, N=47). There was no significant difference in SDA coefficient (energy expended on SDA quantified as a percentage of the energy content of the meal) among different relative meal size groups. Factorial metabolic scope increased from 1.47 to 4.08 when the relative meal size increased from 0.6% to 24%. The peak V O2 increased with meal size, but levelled when relative meal size gradually increased to the maximum. SDA duration showed a S-type (slow-fast-slow) increase course with increased meal size. The results of this study suggest that the high postprandial factorial metabolic scope and a trapezoid SDA curve might be the adaptation strategy of warm water sit-and-wait fish under the natural selection of evolution related to long-term food resources.     

Energetic costs at different levels of feeding in juvenile cod, Gadus morhua L.

The energetic costs associated with feeding by juvenile cod were determined by means of an open-circuit respirometer. Fish acclimated to several temperatures (7, 10, 15 and 18°C) were kept at natural lighting levels, and fed inside their individual respirometers. They consumed a diet compounded from natural foods, at five different ration levels, their oxygen consumption being monitored continually over an 11–16 day period.
After each meal the rate of oxygen consumption increased to above the pre-feeding level, reaching a peak 8–10 h later. With each successive meal the oxygen consumption showed a cumulative increase, reaching a maximum usually after the last meal.
The elevation in metabolic rate associated with feeding was dependent upon ration size, increasing linearly as the food intake increased. The effect was also dependent upon temperature; for fish fed to satiation the total energy cost was equivalent to 11.9, 10.9, 16.4 and 17.1% of the ingested energy at 7, 10, 15 and 18°C respectively. For resting satiated fish the rate of oxygen consumption was close to the maximum rate for active fish.     

Cooking and grinding reduces the cost of meat digestion

The cooking of food is hypothesized to have played a major role in human evolution partly by providing an increase in net energy gain. For meat, cooking compromises the structural integrity of the tissue by gelatinizing the collagen. Hence, cooked meat should take less effort to digest compared to raw meat. Likewise, less energy would be expended digesting ground meat compared to intact meat. We tested these hypotheses by assessing how the cooking and/or grinding of meat influences the energy expended on its digestion, absorption, and assimilation (i.e., specific dynamic action, SDA) using the Burmese python, Python molurus. Pythons were fed one of four experimental diets each weighing 25% of the snake's body mass: intact raw beef, intact cooked beef, ground raw beef, and ground cooked beef. We measured oxygen consumption rates of snakes prior to and up to 14 days following feeding and calculated SDA from the extra oxygen consumed above standard metabolic rate. Postprandial peak in oxygen consumption, the scope of peak rates, and SDA varied significantly among meal treatments. Pythons digesting raw or intact meals exhibited significantly larger postprandial metabolic responses than snakes digesting the cooked ground meals. We found cooking to decrease SDA by 12.7%, grinding to decrease SDA by 12.4%, and the combination of the two (cooking and grinding) to have an additive effect, decreasing SDA by 23.4%. These results support the hypothesis that the consumption of cooked meat provides an energetic benefit over the consumption of raw meat.