Meeting Abstract

P2.165  Monday, Jan. 5  Geographic and Seasonal Variation of Reproductive Steroids in the Diamondback Terrapin, Malaclemys terrapin COLEMAN, A. T.*; WIBBELS, T.; ROOSENBURG, W.; MARION, K.; Univ. of Alabama at Birmingham; Univ. of Alabama at Birmingham; Ohio Univ.; Univ. of Alabama at Birmingham colemana@uab.edu

The diamondback terrapin, Malaclemys terrapin, is the only turtle in North America that exclusively inhabits the brackish environments of bays and estuaries. Studies have examined reproductive steroid levels in several turtle species. This information has been crucial in elucidating certain physiological and ecological aspects such as reproductive activity, stress levels, and sex ratios. In the current study, testosterone and estrogen levels were measured via radioimmunoassay (RIA) of blood samples from two populations of diamondback terrapins. One is a declining population located in the salt marshes of the Patuxent River region of Maryland. The other population is located in the salt marshes surrounding Dauphin Island, Alabama, and has experienced a significant decline from historic levels. Seasonal cycles of reproductive steroids were examined. Adult females showed a gradual decrease in testosterone over the nesting season, whereas, adult males showed a gradual increase, peaking in late summer. Estrogen levels over the nesting season will be reported. The results provide insight into the endocrine physiology underlying the reproductive cycle in the terrapin. They also provide information regarding the number of reproductively active individuals in a population and represent better indicators of maturity than age. A geographical comparison will be conducted to observe variation in steroid levels between two populations that experience different climate regimes. This information will be compared to those of marine and freshwater turtles to better understand how the physiology of the diamondback terrapin has evolved to adapt it to its unique marine niche.