Validating mammalian resistance to stressor-mediated reproductive impact using rodent sperm analysis.

Small rodents from chemically and radiologically contaminated areas on the Savannah River Site, SC were evaluated for sensitive reproductive parameters in a dual purpose study. The primary intent was to observe if established reproductive thresholds-for effect could be exceeded in animals that, due to their restricted home ranges, are maximally exposed to local contamination. Secondarily, validation was sought for a principal element of the Rodent Sperm Analysis method that is used in support of ecological risk assessments for contaminated terrestrial properties. The method's fundamental underlying premise is that during decades of elapsed time between contamination release events and ecological assessments being conducted, rodents develop a resilience to potential stressors, evidenced by their continuing presence. During spring 2014 we collected 89 cotton mice (Peromyscus gossypinus) across three contaminated locations and one reference location, and quantified important male and female reproductive parameters (sperm counts and sperm morphology, and ovarian follicle counts, respectively) and organ weights. The outcome of the comprehensive sperm parameter review, in conjunction with the parallel female reproduction review and other corroborative population and tissue-based information gathered, suggests that mammalian assessments at contaminated sites are unnecessary in the common case.