The Constraints Of Exchange Surface Area And Metabolic Level On Metabolic Scaling Of Crucian Carp (Carassius Auratus)

In this study,the crucian carp(Carassius auratus)were used to study the body mass(M)scaling of resting metabolic rate(RMR),body surface area(BSA),gill surface area(GSA),total surface area(TSA),ventilation frequency(VF),and oxygen consumption per ventilation(OCPV).The influence of the exchange area on RMR and the constraints of exchange area and metabolic level on metabolic scaling were analyzed by processing of temperature,gill shearing and starvation.The “exchange surface area-metabolic demand constraints” hypothesis were tested in this study.The results were as follows:1.RMR of crucian carp scaled with M by a scaling exponent of 0.811,significantly higher than 3/4(p = 0.010).BSA,GSA and TSA of crucian carp scaled with M by scaling exponents of 0.688,0.957 and 0.847,respectively,which were significantly higher than 2/3(p < 0.001).BSA was negatively related to RMR(r =-0.316,p = 0.012),but not GSA(p = 0.321)and TSA(p = 0.890)after controlling for M.b RMR was significantly higher than b BSA(p < 0.001),while lower than b GSA(p < 0.001).There was no significant difference between b RMR and b TSA(p = 0.147).2.VF and OCPV scaled with M by scaling exponents of-0.260 and 1.046,respectively.VF was positively related with RMR(p < 0.001),while the OCPV was not related with RMR(p = 0.063).3.The RMR at 25 oC was significantly higher than that at 15oC(p < 0.001),while there was no significant differences of the BSA,GSA and TSA between temperatures(p > 0.05).The VF and OCPV at 25 oC were significantly higher than those at 15oC(p <0.05).The b RMR at 25 oC was significantly lower than that at 15oC(p < 0.05),while the b BSA,b GSA,and b TSA were significantly higher than those at 15oC(p < 0.05).The b VF at 25 oC was significantly lower than that at 15oC(p < 0.05),while there was no significant difference of the b OCPV between temperatures(p = 0.383).4.The mass specific resting metabolic rate(Ms-RMR)after acclimation for 1 month was signicantly lower than those of the gill sheared fish of control and immediately after shearing gill(p < 0.05),but there was no significant difference between the control and after shearing gill(p > 0.05).There was no significant difference of b RMR among the three groups(p > 0.05).The VF and OCPV after shearing gill and acclimation for 1 month were signicantly higher than those of the control(p < 0.05).There was no significant difference of b OCPV among groups(p > 0.05).5.The Ms-RMRs of the fish after starvation for 1,2,and 4 weeks were significantly lower than those of the control(p = 0.010).The Ms-RMR of fish starvated for 2 weeks was significantly lower than that for 1 week(p < 0.05),while there was no significant difference between for 2 weeks and 4 weeks(p = 0.871).There was no significant difference of b RMR among groups(p > 0.05).The conclusions of this study were as follows:1.GSA was not related with RMR,suggesting that the metabolic scaling of crucian carp is not constricted by GSA,which could be due to that only a fraction of the secondary lamellas contribute to gas exchange for the fish at the resting state.There was no difference between b RMR and b TSA,which indicates same mass scaling for RMR and TSA,and the heat transfer related TSA constricts b RMR.b GSA higher than 2/3 can be attributed to the folded structure of gills.As the b BSA and b TSA were higher than 2/3,it suggsets that,the mass scaling exponent of exchange surface can not be assumed simply as 2/3.2.Higher temperature did not affect the exchange surface area,increase in metabolic level,but decrease in b RMR,which suggests a negative relation between metabolic level and b RMR after controlling for exchange area.3.The RMR and b RMR did not change before and after shearing gills,which implies the crucian carp can recover from gill damage within a short time.The result suggests that crucian carp meets its metabolic need by faster breathing,but not the oxygen obtained per ventilation,and the adjustment can be finished within the short term.4.b RMR was not influenced by starvation,which indicats starvation has the same affects on individuals of different size.