REDUCTION IN PENIS SIZE AND PLASMA TESTOSTERONE CONCENTRATIONS IN JUVENILE ALLIGATORS LIVING IN A CONTAMINATED ENVIRONMENT

The development of the male reproductive ducts and external genitalia in vertebrates is dependent on elevated androgen concentrations during embryonic development and the period of postnatal growth. We have obs erved that a population of juvenile alligators living on Lake Apopka e xhibit significantly smaller penis size (24% average decrease) and low er plasma concentrations of testosterone (70% lower concentrations) wh en compared to animals of similar size on Lake Woodruff. In addition t o smaller phalli, no relationship exists between plasma testosterone c oncentrations and penile size in males from Lake Apopka, whereas a pos itive relationship exists for males from lake Woodruff. The alligators on Lake Apopka are known to have elevated concentrations of the antia ndrogenic DDT breakdown product p,p'-DDE stored in their fat. We sugge st a number of hypotheses that could explain the modification in the p henotype of the juvenile male living in Lake Apopka. These modificatio ns in phenotype include a smaller penis size, lower plasma androgen co ncentrations, and lack of responsiveness of the penis to the plasma an drogens present. (C) 1996 Academic Press, Inc.