Meeting Abstract
Exposure to pesticides, especially in early life stages, may negatively impact amphibian populations. These effects may arise as a function of direct mortality of individuals, but indirect effects such as impacts on hormonal regulation of homeostasis or of other necessary survival traits, can also negatively impact populations. Corticosterone (CORT) is the main amphibian stress hormone, and elevations of CORT can interfere with antipredator responses. We examined the synergistic effects of an herbicide, Roundup (active ingredient = glyphosate), and exogenous CORT on tadpole growth, CORT and antipredator responses in Incilius nebulifer. We exposed tadpoles for 7 days to one of 4 treatments: exogenous CORT, Roundup, CORT plus Roundup, and control. We then measured water-borne CORT release rates and placed the tadpoles in fresh water, we then exposed tadpoles to dragonfly nymph predator diet cues. We measured tadpole activity before and after exposure to the predator cue, then measured water-borne CORT release rates of each tadpole. We found that tadpoles exposed to CORT or CORT plus Roundup had significantly higher CORT release rates prior to predator exposure than those in the other two treatments, but CORT after exposure to the predator cues did not differ across treatments. CORT release rates after exposure to predators were the same as the initial control treatment release rates. Tadpoles decreased activity in response to predator cues in all but the CORT plus Roundup treatments, and the tadpoles from the CORT plus Roundup treatments were also the least active overall. We conclude that there are synergistic effects of Roundup and CORT on the behavior and physiology of Incilius nebulifer tadpoles, indicating that more stressed tadpoles are less likely to survive predator attacks when exposed to the herbicide Roundup.
