IMPACT OF ORGANOCHLORINE CONTAMINATION ON LEVELS OF SEX-HORMONES AND EXTERNAL MORPHOLOGY OF COMMON SNAPPING TURTLES (CHELYDRA-SERPENTINA SERPENTINA) IN ONTARIO, CANADA

Recent research has suggested that contaminants in the environment may influence sex differentiation and reproductive endocrine function in wildlife. Concentrations of organochlorine contaminants (total polychl orinated biphenyls, pesticides) were higher in the blood plasma of sna pping turtles from contaminated sites than in those from reference sit es. The ratio of the precloacal length to the posterior lobe of the pl astron (PPR) is sexually dimorphic in snapping turtles. There were sig nificant reductions in the PPR at three contaminated sites versus two reference sires. The magnitude of che response was such that a signifi cantly higher proportion of PPRs of males hom a contaminated site (Coo tes Paradise) overlapped with those of females than PPRs of males from a reference site (Lake Sasajewun). Observers can incorrectly identify the sex of turtles ar the contaminated site based on secondary sexual characteristics alone. Unlike the changes to the morphology, there we re few changes in 17 beta-estradiol or testosterone levels, and where differences occurred, there was more variation among reference sites t han between the reference and contaminated sires. Our results suggest that environmental contaminants may affect sexually dimorphic morpholo gy in snapping turtles without affecting circulating testosterone or e strogen levels in the adults.