Yiping Luo

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 283.2 mg O(2) kg(-1) h(-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=4.28 M+10.62 (r(2)=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.

Intraspecific Scaling of the Resting and Maximum Metabolic Rates of the Crucian Carp (Carassius auratus)

The question of how the scaling of metabolic rate with body mass (M) is achieved in animals is unresolved. Here, we tested the cell metabolism hypothesis and the organ size hypothesis by assessing the mass scaling of the resting metabolic rate (RMR), maximum metabolic rate (MMR), erythrocyte size, and the masses of metabolically active organs in the crucian carp (Carassius auratus). The M of the crucian carp ranged from 4.5 to 323.9 g, representing an approximately 72-fold difference. The RMR and MMR increased with M according to the allometric equations RMR = 0.212M 0.776 and MMR = 0.753M 0.785. The scaling exponents for RMR (b r) and MMR (b m) obtained in crucian carp were close to each other. Thus, the factorial aerobic scope remained almost constant with increasing M. Although erythrocyte size was negatively correlated with both mass-specific RMR and absolute RMR adjusted to M, it and all other hematological parameters showed no significant relationship with M. These data demonstrate that the cell metabolism hypothesis does not describe metabolic scaling in the crucian carp, suggesting that erythrocyte size may not represent the general size of other cell types in this fish and the metabolic activity of cells may decrease as fish grows. The mass scaling exponents of active organs was lower than 1 while that of inactive organs was greater than 1, which suggests that the mass scaling of the RMR can be partly due to variance in the proportion of active/inactive organs in crucian carp. Furthermore, our results provide additional evidence supporting the correlation between locomotor capacity and metabolic scaling.

Intraspecific metabolic scaling exponent depends on red blood cell size in fishes

ABSTRACT The metabolic-level boundaries (MLB) hypothesis and the cell metabolism (CM) hypothesis have been proposed to explain the body mass scaling of metabolic rate. The MLB hypothesis focuses mainly on the influence of the metabolic level on the relative importance of volume and surface area constraints. The CM hypothesis focuses on the variation of cell size as the body grows. The surface area to volume ratio of individual cells may vary among species with different cell sizes, by which surface area constraints on metabolic scaling may change according to the MLB hypothesis. The present study aimed to extend the MLB and the CM hypotheses by proposing that, in addition to metabolic level, the varying cell surface area constraints among species also influence the intraspecific scaling exponents. The red blood cell area (S), and intraspecific scaling exponents for resting (bR) and maximum metabolic rates of four species of cyprinids were assessed. The scaling exponents varied among species, but mass-specific resting metabolic rates (RMR) of each species were similar. No significant correlation was found between S and mass-specific RMR among species. As predicted, a significantly negative relationship exists between S and bR among species. The results suggest that the varying bR could be attributed to cell size differences among species, as those with larger cells may face stronger surface boundary limits, as predicted by the MLB hypothesis. This mechanism represents an additional way of relating the MLB and the CM hypotheses and does not exclude another mechanism based on the recent contextual multimodal theory. Summary: An integrative mechanism of metabolic scaling is proposed: species with a larger cell size have a smaller metabolic scaling exponent as they face more pronounced surface/volume limits.

Effects of starvation on the excess post-exercise oxygen consumption of juvenile Nile tilapia (Oreochromis niloticus)

The resting metabolic rate (MO2rest) of juvenile Nile tilapia (Oreochromis niloticus) decreased from 264.5 to 189.4 mg O2 kg−1 h−1 after one week of starvation and the maximum post-exercise oxygen consumption (MO2peak) decreased from 1032.5 to 647.4 mg O2 kg−1 h−1. MO2 rest and MO2peak decreased further to 166.5 and 463.3 mg O2 kg−1 h−1 respectively after six weeks of starvation. Furthermore, the duration of the excess post-exercise oxygen consumption (EPOC) decreased from 113.3 to 56.3 min, and the magnitude of EPOC decreased from 276.8 to 100.2 mg O2 kg−1. We conclude that tilapia are very sensitive to food shortage and rapidly reduce their energy expenditure. The decreased metabolic scope and EPOC imply that both aerobic and anaerobic metabolic capacities are reduced in starved tilapia, possibly as a result of glycogen depletion. We suggest that food deprivation should not exceed one week when Nile tilapia are used as experimental fish.

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 degrees 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.

Mass scaling of the resting and maximum metabolic rates of the black carp

We investigated the body mass (M) scaling of resting metabolic rate (RMR), maximum metabolic rate (MMR), excess post-exercise oxygen consumption (EPOC), blood parameters, and organ masses of black carp (Mylopharyngoden piceus). The results showed that RMR scaled with M of the fish by an exponent (b) of 0.833 (bR), which was significantly larger than 0.75. MMR scaled with M by a power of 0.775 (bM), which was significantly lower than 1 and may be due to a small size proportion of red muscle. No difference between bR and bM or correlation between factorial aerobic scope and M was found. However, EPOC scaled positively with M by a power of 1.231, suggesting a constant aerobic capacity and an enhanced anaerobic capacity with fish growth. Mass of the inactive organs scaled with M by a power of 1.005, which was significantly larger than 1 and was negatively correlated with RMR, suggesting that the proportion of inactive organs increases with fish growth, which may contribute to the negative scaling of RMR. Red blood cell surface area (S) did not increase with increasing M, suggesting that the ontogenetic decrease in the surface area to volume ratio of cells may not contribute to the negative scaling of RMR. The predicted bR value (0.846) by the average S (1.746 µm²) differs by only 1.62% from the observed bR value using our previously reported S − bR function in carp, suggesting that the species-specific cell size, rather than its ontogenetic change, affects the metabolic scaling of a species.

Are the surface areas of the gills and body involved with changing metabolic scaling with temperature

ABSTRACT The metabolic-level boundaries (MLB) hypothesis proposes that metabolic level mediates the relative influence of surface area (SA)- versus volume-related metabolic processes on the body-mass scaling of metabolic rate in organisms. The variation in the scaling of SA may affect how metabolic level affects the metabolic scaling exponent. This study aimed to determine the influence of increasing metabolic level at a higher temperature on the metabolic scaling exponent of the goldfish and determine the link between metabolic scaling exponents and SA parameters of both gills and body. The SA of gills and body and the resting metabolic rate (RMR) of the goldfish were assessed at 15°C and 25°C, and their mass scaling exponents were analyzed. The results showed a significantly higher RMR, with a lower scaling exponent, in the goldfish at a higher temperature. The SA of the gills and the total SA of the fish (TSA) were reduced with the increasing temperature. The scaling exponent of RMR (bRMR) tended to be close to that of the TSA at a higher temperature. This suggests that temperature positively affects metabolic level but negatively affects bRMR. The findings support the MLB hypothesis. The lower scaling exponent at a higher temperature can be alternatively explained as follows: the higher viscosity of cold water impedes respiratory ventilation and oxygen uptake and reduces metabolic rate more in smaller individuals than in larger individuals at lower temperature, thus resulting in a negative association between temperature and bRMR. Summary: In the goldfish, temperature positively affects metabolic level but negatively affects the scaling exponent of resting metabolic rate, supporting the metabolic-level boundaries hypothesis.

Body and organ metabolic rates of a cave fish, Triplophysa rosa: influence of light and ontogenetic variation

Triplophysa rosa is a typical species of cave-dwelling fish distributed throughout Wulong County, Chongqing, China. This study aimed to test whether T. rosa has a low metabolic level as a cave species and how the metabolic rate of this fish responds to light stimulation. The whole body and organ (including brain, heart, and liver) oxygen consumption rates (

Effects of temperature on the specific dynamic action of the southern catfish, Silurus meridionalis.

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