Plasma Dihydrotestosterone Concentrations and Phallus Size in Juvenile American Alligators (A. mississippiensis) from Contaminated and Reference Populations

Abstract

Evidence increasingly suggests that some environmental pollutants are able to permanently affect development of the endocrine system in wildlife. Embryonic and neonatal exposure to these endo- crine-disrupting contaminants can cause structural and functional abnormalities of the reproductive system. It has recently been hypothesized that demasculinization of a population of male juvenile American alli- gators (Alligator mississippiensis) from Lake Apopka, Florida, could result from exposure to antiandrogenic contaminants. The persistent pesticide contaminant p.p'-DDE interacts with the mammalian androgen recep- tor and antagonizes androgen action in vivo. Wildlife from Lake Apopka, which has been contaminated through agriculture and an industrial accident, exhibit elevated levels of p.p.'-DDE, among other pesticide residues. This study provides further evidence of reproductive dysfunction in Lake Apopka juvenile alli- gators by comparison with a reference population from a relatively uncontaminated lake nearby, Lake Woodruff National Wildlife Refuge. Phallus size correlated strongly with plasma dihydrotestosterone (DHT) concentrations or body size in juvenile males from Lake Woodruff In contrast, males from Lake Apopka had significantly smaller phalli (adjusted for body size) than those from Lake Woodruff, and correlations with body size or plasma DHT concentrations were weak or absent. Plasma DHT concentrations did not differ significantly between juvenile males from the two lakes. In contrast, plasma DHT concentrations were significantly higher in females from Lake Apopka compared to those from Lake Woodruff This is the first report of masculinized female juvenile alligators from Lake Apopka and suggests that juveniles of both sexes exhibit altered endocrine and reproductive parameters.