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MP13 Aquatic Ecotoxicology
(TOL-1117-839399) The effects of polychlorinated biphenyls on gonadal differentiation in the gray tree frog (Hyla chrysoscelis).
Tolley, A1, Bailey, F1, 1 Middle Tennessee State University, Murfreesboro, TN, USA
ABSTRACT- A growing number of studies are being conducted to determine the cause of amphibian declines. Polychlorinated biphenyls (PCBs) are one group of chemical contaminants that pose a health risk to amphibians. In laboratory studies, PCBs have been shown to cause increased mortality, reductions in body size, increased time to metamorphosis, and histological abnormalities in tadpoles. PCBs are known endocrine disruptors and can act as estrogen mimics by binding to the estrogen receptors. This action has been shown to affect gonadal differentiation in a number of vertebrate species. The purpose of this study was to determine if PCB contamination affects gonadal differentiation in the gray treefrog, Hyla chrysoscelis. Gray treefrog eggs were exposed to sediments dosed with either 10ppm or 100ppm Arochlor 1254, an acetone solvent control or 100ppm estradiol as a positive control for estrogenic effects. Forty eggs were placed into each of the four treatments with four replicates per treatment. Eggs were allowed to hatch and tadpoles remained in the treatments until metamorphosis. Upon metamorphosis, froglets were weighed, examined for morphological abnormalities and placed in 10% formalin until histological examination. Froglets in the 100 ppm group weighed significantly less than those in control and 10 ppm groups but not the estradiol group. Hatchability was higher in the estradiol group than in the 10 and 100ppm groups but not the control group. Morphological abnormalities were observed in the estradiol group with 20% of individuals having extra toes on limbs and in the 100 ppm group with 29% of individuals having fewer toes on limbs. No behavioral abnormalities were observed in any group. Histological examination of gonads is being conducted and five froglets from each treatment are being analyzed for PCB total body burdens.
Key words: PCBs, amphibian, endocrine disruption, gonadal differentiation
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