Effects Of Temperature On Metabolic Scaling And Exchange Surface Area Of Silver Carp And Bighead Carp

The mechanisms of mass scaling of metabolic rate of animals remains unsolved.As temperature increases,metabolic demand increases,which may intensify the constraints of exchange surface on metabolic scaling and reduces metabolic scaling exponents.Meanwhile,exchange surface area of animals may change as temperature changes,which could change its constraints on metabolic scaling.It remains unclear whether a negative correlation generally exists among species,and whether exchange surface area changes with increasing temperature,and whether this change influence metabolic scaling exponent.In this study,silver carp(Hypophthalmichthys molitrix)and bighead carp(Hypophthalmichthys molitrix)were used as experimental animals.The resting metabolic rate(RMR),red blood cell size(SRBC),red blood cell metabolic rate(MRRBC),gill area(GSA),body surface area(BSA),total surface area(TSA),height of the interlamellar cell mass(ICMH),and gill lamellar prominent height(PLH)were measured in the fish with different body mass at 10 and 25 ℃,respectively.The mass scaling relationships of those parameters was analyzed.Furthermore,the effects of temperature and species on exchange area and metabolic scaling were analyzed.The results were as follows:1.At 10 ℃,the individual RMR of the silver carp positively correlated with M by a scaling exponent of 0.792,not different to 3/4.The RMR positively correlated with M of the bighead carp by a scaling exponent of 0.702,not significantly different to 3/4.The individual RMR of the bighead carp was larger,while its scaling exponent was smaller than that of the silver carp.At 25 ℃,the individual RMR of the silver carp positively correlated with M,by a scaling exponent of 0.760,not significantly different to 3/4.The individual RMR of bighead carp positively correlated with M,by a scaling exponent of 0.820,not significantly different to 3/4.The RMR of the bighead carp was larger,and its scaling exponent was not different to that of the silver carp.The RMR of the both two species was high at 25 ℃ compared at 10 ℃,but the scaling exponent of RMR was not significantly different between temperatures.2.At 10 ℃,the SRBC of both silver carp and bighead carp were not significantly correlated with M.The SRBC of the silver carp was smaller than that of the bighead carp.At 25 ℃,the SRBC significantly correlated with M in the bighead carp by a scaling exponent of 0.048,but not in the silver carp.The SRBC of the silver carp was smaller than that of the bighead carp.There was no significant difference in the SRBC of silver carp and bighead carp between the two temperatures.3.At 10 ℃,the MRRBC of the silver carp did not correlate with M.However,MRRBC of the bighead carp negatively correlated with M by a scaling exponent of-0.197.At 25 ℃,MRRBC of both silver carp and bighead were unrelated with M.There was no significant difference of MRRBC in both silver carp and bighead carp between temperatures.4.At 10 ℃,the GSA of both silver carp and bighead carp positively correlated with M by scaling exponents of 0.903 and 0.883,respectively.There was no significant difference of GSA in both silver carp and bighead carp.At 25 ℃,the GSA of both silver carp and bighead carp positively correlated with M by scaling exponents of 0.928 and 0.836,respectively.The GSA of the bighead carp was larger than that of the silver carp.The GSA of silver carp at 10 ℃ was significantly greater than that at 25 ℃.There was no significant difference in GSA and its scaling exponent of bighead carp between two temperatures.5.At 10 ℃,the BSA of both silver carp and bighead carp positively correlated with M,by scaling exponents of 0.643 and 0.674,respectively.The BSA of silver carp was significantly greater than that of the bighead carp.At 25 ℃,the BSA of both silver carp and bighead carp positively correlated with M by scaling exponents of 0.665 and 0.683,respectively.The BSA of the silver carp was significantly greater than that of the bighead carp.There was no significant difference in BSA and its scaling exponent between the two temperatures.6.At 10 ℃,the TSA of both silver carp and bighead carp positively correlated with M by scaling exponents of 0.813 and 0.802,respectively.There was no significant difference of TSA in both silver carp and bighead carp.At 25 ℃,the TSA of both silver carp and bighead carp positively correlated with M by scaling exponents of 0.817 and 0.794,respectively.The scaling exponents of TSA of both silver carp and bighead carp were significantly different to scaling exponents of RMR at this temperature.The TSA of bighead carp was significantly higher than that of silver carp.There was no significant difference in scaling exponents of both silver carp and bighead carp between two temperatures.7.At 10 ℃,ICMH of both silver carp and bighead carp positively correlated with M by scaling exponents of 0.182 and 0.114,respectively.There was no significant difference of ICMH in both silver carp and bighead carp.At 25 ℃,ICMH of both silver carp and bighead carp positively correlated with M by scaling exponents of 0.145 and 0.148,respectively.The ICMH of the bighead carp was significantly larger than that of the silver carp.There was no significant difference in ICMH of both silver carp and bighead carp between the two temperatures.8.At 10 ℃,the PLH of the bighead carp positively correlated with M by a scaling exponent of 0.195.The PLH of the silver carp did not correlate with M.The PLH of the bighead carp was significantly larger than that of the silver carp.At 25 ℃,the PLH of both silver carp and bighead carp positively correlated with M by scaling exponents of 0.160 and 0.089,respectively.The PLH of the bighead carp was significantly larger than that of the silver carp.The PLH of the silver carp at 25 ℃ was significantly greater than that at 10 ℃.Conclusion: 1.Compared with 10℃,the resting metabolic rates of silver carp and bighead carp were increased at 25℃.However,the scaling exponent of metabolic rate was not significant difference,which did not supports with the metabolic-level boundaries hypothesis.2.The red blood cell area of silver carp and bighead carp had no change or little change with individual growth.Individual growth mainly depended on the increase in the number of cells,and the scaling exponent of metabolic rate tended to 1.However,because the red blood cell size of silver carp and bighead carp at two temperatures do not relate to resting metabolic rate,it does not support the theory of cell metabolism hypothesis.3.At 10℃,the scaling exponent of metabolic between silver carp and bighead consistent with the metabolic-level boundaries hypothesis and the surface area-metabolic demand hypothesis.At 25℃,the scaling exponent of metabolic between silver carp and bighead consistent with the surface area-metabolic demand hypothesis,not consistent with the metabolic-level boundaries hypothesis.