Effects of gill excision and food deprivation on metabolic scaling in the goldfish Carassius auratus.

Abstract

According to the metabolic-level boundaries hypothesis, metabolic level mediates the relative influence of surface area or volume-related metabolic processes on metabolic scaling in organisms. Therefore, variation in both metabolic level and surface area may affect metabolic scaling. Goldfish were used to determine the influence of both a surgical reduction in respiratory surface area and food deprivation on metabolic scaling exponents (bR ). Gill excision did not change resting metabolic rate (RMR) or bR (a common value of 0.895). However, ventilation frequency (VF) increased from 21.6 times min-1 before gill excision to 52.8 times min-1 after gill excision. This suggests that the acceleration of breathing after gill excision offsets the constraints of the respiratory surface area on RMR and results in no influence of surface area reduction on metabolic scaling. In the food deprivation experiment, RMR decreased; however, bR (a common value of 0.872) did not increase. The VFs of the fish at weeks 1 and 2 were approximately 22% and 38% lower than that at Week 0, which may enhance exchange surface area limits and result in no increase in bR with a decreasing RMR induced by food deprivation. The results suggest that food deprivation reduces metabolic level, but does not alter metabolic scaling exponent owing to variation in VF.