Comparison of metabolic scaling between triploid and diploid common carp

Ploidy level affects both the cell size and metabolic rate (MR) of organisms. The present study aimed to examine whether ploidy levels cause differences in cell surface area (SA), MR and metabolic scaling. The resting MR (RMR), red blood cell SA (SA_RBC), red blood cell count (RBCC), gill SA (GSA), and ventilation frequency (VF) were measured in diploid and triploid common carp with different body masses (M). The results showed that both M and ploidy level affected the RMR, GSA, VF, and SA_RBC, with interactions between M and ploidy level. The triploids had larger SA_RBC but lower RBCC than those of the diploids. The SA_RBC increased weakly but significantly with increasing M, by an exponent of 0.043, in the triploids but did not increase in the diploids. The RMR of the triploids and diploids scaled with M, by exponents of 0.696 and 1.007, respectively. The RMR was higher in the triploids than the diploids. The GSA scaled with M, with an exponent of 0.906 in the triploids and an exponent of 1.043 in the diploids. The VF scaled with M by an exponent of - 0.305 in the triploids but showed no correlation with M in the diploids. The larger SA_RBC and RMR and smaller scaling exponents of both the GSA and VF of the triploids were consistent with the finding that the b_R was smaller in the triploids than in the diploids. This suggests that the ploidy-induced changes of SA and SA scaling affect the metabolic scaling of fish.