M9 PM Multiple Stressors in Amphibian and Reptile Ecotoxicology
Monday, 14 November 2005: 1:50 PM - 5:30 PM in 339-340

(WID-1117-833498) Effects of exposure to chlorpyrifos on tadpole growth and behavioral measures in four species.

Widder, P¹, Bidwell, J¹, ¹ Oklahoma State University, Stillwater, Oklahoma, USA

ABSTRACT- Recent studies have reported a correlative connection between agricultural chemicals and reductions in amphibian populations. However, supplementing these studies with ecologically based laboratory investigations will help facilitate a definitive connection between agricultural chemicals and the loss of amphibian populations. In this study, we examined how a commonly used organophosphate pesticide (OP), chlorpyrifos, impacted the response of tadpole cholinesterase (ChE; the biomarker of exposure to OPs), growth, and swim speed in four species of amphibians (Hyla chrysoscelis, Rana sphenocephala, Acris crepitans, and Gastrophryne olivacea) using laboratory tests with an environmentally realistic experimental design. This design included five environmentally relevant concentrations of chlorpyrifos and examined the influence of pond sediment on tadpole responses after four days. In two species, we also examined how a longer exposure (twelve days) influenced these same responses. Chlorpyrifos exposure significantly impacted tadpole mass in H. chrysoscelis (p=0.0131) and ChE in all species. H. chrysoscelis ChE activity was the most sensitive and R. sphenocephala the least. We found that both sediment and longer duration influenced both these responses in an inconsistent pattern among species. Tadpole swim speed was significantly impaired only in H. chrysoscelis tests without the presence of sediment, despite the inhibition level of 75% in sediment treatments and inhibition of ChE up to 90% in the other species. Furthermore, individual ChE activity did not correlate with individual swim speed. These results indicate that exposure to chlorpyrifos in environmentally realistic scenarios may have a significant impact on tadpole ChE activity and growth, however, swim speed, and therefore potential predator escape ability, is likely to remain unaffected in a real exposure situation.

Key words: cholinesterase, amphibians, swim speed, tadpole