Sex-Related Differences in Somatic Stored Energy Reserves of Pseudacris crucifer and Pseudacris triseriata during the Early Breeding Season

Abstract

We examined how differences in the allocation of resources influence prebreeding somatic stored energy reserves (fat and glycogen) in males and females of the hylid frogs Pseudacris crucifer and Pseudacris triseriata. Males had shorter snout–vent lengths than did females but similar wet and dry carcass masses. Nonpolar lipid and glycogen contents of the carcass increased with carcass mass in males but not in females. Similarly, triglyceride and glycogen contents of the liver increased more acutely with increasing liver mass in males than in females. Ovarian mass in gravid females correlated with body size and in P. crucifer the gonadal-somatic index increased with increasing body size, indicating a greater than proportional increase in ovary mass with increasing body size. These findings suggest that, during the pre-reproductive period, larger males allocate more energy toward preparation for courtship activity than do smaller males, whereas larger females may allocate more energy toward production of eggs.