PARENT SESSION
Oral Session # 94: Pathogens, Toxins, and Disease III.
Presiding: C Duffie
Friday, August 8. 8:30 AM to 12:00 PM, SITCC Meeting Room 200.

Effects of the herbicide atrazine and food limitation on the survival, life-history, and behavior of streamside salamanders.

Rohr, Jason^*,1, Elskus, Adria¹, Shepherd, Brian¹, Crowley, Philip¹, McCarthy, Thomas¹, Niedzwiecki, John¹, Sih, Andy^{1, 2}, Palmer, Brent¹, ¹ University of Kentucky, Lexington, KY² University of California at Davis, Davis, CA

ABSTRACT- Amphibian populations can be affected adversely by biotic and abiotic stressors that together can contribute to their global decline. Consequently, we evaluated the effects of food abundance (limited and unlimited food) and exposure to ecologically relevant concentrations of atrazine (actual concentrations: 0, 4, 40, 400 ppb), possibly the most abundantly used herbicide in the world, on the survival, life-history, and behavior of streamside salamanders, Ambystoma barbouri, from embryo through metamorphosis. In general, food and atrazine levels did not interact statistically, and atrazine concentration was correlated positively with effect size. Exposure to 400ppb of atrazine decreased embryo survival and increased time to hatching and variation in hatching day. This greater hatching variation amplified larval size variation, facilitating cannibalism. Both cannibalism and limb loss due to biting were more common in food-restricted groups. Despite the significant cannibalism, neither atrazine nor food restriction had overall significant effects on larval survival. However, food-limitation increased larval activity and decreased shelter use, while increasing atrazine concentrations decreased activity and shelter use. Our approach triggered a flee-then-freeze response by larvae exposed to 400 ppb of atrazine. Both food restriction and 400 ppb of atrazine reduced larval growth and size at metamorphosis without affecting body condition, despite atrazine having no effect on feeding rates through ontogeny. Food limitation delayed metamorphosis, while 400 ppb of atrazine shortened the larval period, but the length of the larval period and size at metamorphosis were correlated positively regardless of food or atrazine level. Metamorphic responses to atrazine, food limitation, and release from competition were consistent with the predictions of the Wilbur and Collins amphibian life-history model. Because reduced growth and smaller size at metamorphosis can lower terrestrial survival and lifetime reproduction, resource limitation and environmentally realistic concentrations of atrazine have the potential to contribute to amphibian declines in impacted systems.

Key words: pesticide, amphibian, life-history, behavior