Emerging Pathogens and a Current-Use Pesticide: Potential Impacts on Eastern Hellbenders.

Populations of the eastern hellbender Cryptobranchus alleganiensis alleganiensis have been declining for decades, and emerging pathogens and pesticides are hypothesized to be contributing factors. However, few empirical studies have attempted to test the potential effects of these factors on hellbenders. We simultaneously exposed subadult hellbenders to environmentally relevant concentrations of either Batrachochytrium dendrobatidis (Bd) or a frog virus 3-like ranavirus (RV), a combination of the pathogens, or each pathogen following exposure to a glyphosate herbicide (Roundup). Additionally, we measured the ability of the skin mucosome to inactivate Bd and RV in growth assays. We found that mucosome significantly inactivated RV by an average of 40% but had no negative effects on Bd growth. All treatments that included RV exposure experienced reduced survival compared to controls, and the combination of RV and herbicide resulted in 100% mortality. Histopathology verified RV as the cause of mortality in all RV-exposed treatments. No animals were infected with Bd or died in the Bd-only treatment. Our results suggest that RV exposure may be a significant threat to the survival of subadult hellbenders and that Roundup exposure may potentially exacerbate this threat.