Tradeoffs in Energy Investment for Reproduction Between Sexes in Two Species of Fiddler Crabs

Abstract

All animals must portion their energy in order to reproduce, and energy investment for reproduction may vary by sex. Fiddler crabs invest energy in their hepatopancreas and gonads for reproduction, and males also invest in their major claw. This study looks at how energy investment for reproduction differs by sex in two species of fiddler crab, Minuca pugnax and Leptuca pugilator. Energy investment was determined through analysis of hepatosomatic index (HSI) and gonadosomatic index (GSI). We found that in M pugnax, there was not a significant difference in HSI between males and females, but in L pugilator, females had a significantly higher HSI. M pugnax females had a lower HSI than L. pugilator females. Females in both species had higher GSIs than males, and M. pugnax females had higher GSIs than L. pugilator females. Both HSI and GSI were impacted by month and year. The results suggest that differences in brooding and mating behavior between species leads to differences in which sex may invest more in a particular part of their reproductive biology.