FINKLER, M.S.*; GILLEM, A.D.; Indiana Univ. Kokomo; Indiana Univ. Kokomo: Sex-related differences in stored energy reserves in spring-breeding hylid frogs

The energetic cost of reproduction may be considerably higher for females than for males, not only because of a difference in the amount of energy invested in the gametes but from indirect costs associated with maintenance of support tissues, elevated energetic cost of locomotion, etc. Here, we examined how differences in these reproductive costs might impact stored energy reserves (fat and glycogen) in males and females of two species of hylid frog: the spring peeper, Pseudacris crucifer, and the western chorus frog, Pseudacris triseriata. Although males of both species tend to be slightly smaller than females, their livers were generally larger than were those of females. Moreover, liver mass increased much more with increasing body size in males than in females. Likewise, the liver glycogen contents and carcass non-polar lipid contents were generally higher and increased much more acutely with increasing body size in males than in females. These findings suggest a greater depletion of stored energy reserves in females to fuel a higher pre-courtship energetic cost of reproduction through gamete formation. This in turn may have implications for survivorship during and after the reproductive season.