Amphibians, already threatened, face increased susceptibility to disease from environmental stress

Frogs, salamanders and their kin, which are seen as indicators of environmental conditions, are experiencing extreme population declines linked to an often-deadly fungal infection from Bactrachochytrium dendrobatidis.

Research conducted by Duquesne University biology student Shelby Boord, with faculty advisor Dr. Sarah Woodley, associate professor of biological sciences, supports the hypothesis that environmental stressors increase salamanders' susceptibility to infection, based on chronic exposure to corticosterone, a stress hormone.

In her study, Boord treated red-legged salamanders with either the hormone or oil for nine days before exposing them to the fungal pathogen. Using molecular techniques, she measured infection at baseline, day 10 and day 17. Boord monitored the subjects for disease symptoms for 30 days after exposure.

All of the exposed animals became infected. However, those treated with the hormone had a greater abundance of harmful pathogens than the control group.

Because of this new evidence relating stress hormones with infection rates, the research provides a call to minimize amphibians' exposure to environmental stressors to bolster their disease resistance and allow them to survive in a rapidly changing world.

The U.S. Fish & Wildlife Service notes the decline in amphibians may be more severe and widespread than previously realized. With more than 41 percent of all amphibians at risk of extinction, the International Union for the Conservation of Nature calls them the most threatened vertebrate group.

Boord presented her work at the March 3 Undergraduate Research at the Capitol-Pennsylvania event. Besides Woodley, doctoral student Chris Fonner and Shreya Patel, who received her undergraduate degree in 2014, contributed to the experiment.