Meeting Abstract

58.2  Jan. 6  Differences in organ mass and hematology between male and female Spotted Salamanders (Ambystoma maculatum) during the reproductive season. FINKLER, M.S.; Indiana Univ., Kokomo mfinkler@iuk.edu

Spotted salamanders display pronounced sexual dimorphisms in body size, metabolism, migratory behavior, and whole-animal performance during the reproductive season. Here, I investigated potential differences in heart, liver, gonad, and reproductive duct mass, as well as potential differences in RBC counts, Hct, and total [Hb] between males and females before and after reproduction. Females had larger hearts than males but smaller livers. Moreover, female wet liver mass was lower after reproduction than before. Pre-reproductive ovary mass was 11.7x greater than pre-reproductive testes mass, but post-reproductive ovary mass was only 2.4x that of post-reproductive testes mass. Oviduct mass was 3.9x greater before reproduction than after, whereas mesonephric duct mass was 2.6x greater before reproduction compared to after. Although pre-reproductive males and females had similar RBC counts, post-reproductive females had lower RBC counts. Both Hct and [Hb] were higher in males than in females, and both were lower after reproduction than before reproduction in females. These findings suggest that the degree of reproductive organ proliferation is greater in females than in males. Moreover, post-reproductive decreases in liver mass and hematological parameters observed in females suggest that physiological costs of reproduction (e.g., stored energy reserves, aerobic capacity, etc.) may be greater in females than in males. Such costs may underlie behavioral, demographic, and morphological dimorphisms in Ambystomatids.