P1.122 Wednesday, Jan. 4 Dimorphism on the Inside: Differences in Visceral Organ Mass between Male and Female Spring Peepers (Pseudacris crucifer). FINKLER, M.S.; Indiana Univ. Kokomo email@example.com
Studies of sexual dimorphism rarely consider differences in the size of internal structures, although dimorphisms in internal anatomy may exist even when the external morphologies of males and females are similar. In this study I examined differences in the masses of the heart, liver, and kidneys between male and female Spring Peepers (Pseudacris crucifer) early in their reproductive season. Both heart mass and liver mass were significantly greater in males that in females, and increased more acutely with body size in males than in females. In contrast, there was no difference in kidney mass between males and females. These findings highlight sex-related differences in somatic organ size that have heretofore received little consideration in investigations of the evolution of sexual dimorphism. Notably, the relatively larger size of the heart and liver in males reflects differences in activity and energy expenditure between males and females during the breeding season.