Alligators and endocrine disrupting contaminants: A current perspective

Many xenobiotic compounds introduced into the environment by human activity have been shown to adversely affect wildlife. Reproductive disorders in wi ldlife include altered fertility, reduced viability of offspring, impaired hormone secretion or activity and modified reproductive anatomy, It has bee n hypothesized that many of these alterations in reproductive function are due to the endocrine disruptive effects of various environmental contaminan ts. The endocrine system exhibits an organizational effect on the developin g embryo. Thus, a disruption of the normal hormonal signals can permanently modify the organization and future function of the reproductive system. We have examined the reproductive and developmental endocrinology of several populations of American alligator (AL ligator mississippiensis) living in c ontaminated and reference lakes and used this species as a sentinel species in held studies. We have observed that neonatal and juvenile alligators li ving in pesticide-contaminated lakes have altered plasma hormone concentrat ions, reproductive tract anatomy and hepatic functioning. Experimental stud ies exposing developing embryos to various persistent and nonpersistent pes ticides, have produced alterations in gonadal steroidogenesis, secondary se x characteristics and gonadal anatomy. These experimental studies have begu n to provide the causal relationships between embryonic pesticide exposure and reproductive abnormalities that have been lacking in pure field studies of wild populations, An understanding of the developmental consequences of endocrine disruption in wildlife can lead to new indicators of exposure an d a better understanding of the most sensitive life stages and the conseque nces of exposure during these periods.