PM11 Wildlife Ecotoxicology
Exhibit Hall
8:00 AM - Monday
(PM183) Gross morphology and gonad histology of ranid frog species collected from atrazine-exposed sites in Michigan.
Tompsett, A1, Murphy, M1, Coady, K2, Hecker, M1, DuPreez, L3, Jones, P1, Giesy, J1, Carr, J4, Van Der Kraak, G5, Kendall, R4, 1 Michigan State University, East Lansing, MI, USA2 Entrix, Inc., Okemos, MI, USA3 North-West University, Potchefstroom, South Africa4 Texas Tech University, Lubbock, TX, USA5 University of Guelph, Guelph, ON, Canada
ABSTRACT- Exposure to atrazine has been reported to cause gonadal deformities in frogs in laboratory exposures, but little is known about possible effects on wild frog populations. Adult and juvenile green frogs (Rana clamitans), American bullfrogs (Rana catesbeiana) and northern leopard frogs (Rana pipiens) were collected throughout the summers of 2002 and 2003 from fifteen field sites in central Michigan representing a range of atrazine exposure concentrations. Atrazine concentrations were greatest in early to mid-summer, ranging from <0.22 to >250 
g/L among locations. All frogs were examined for gross gonadal abnormalities, and one gonad from each frog was removed for histological analysis. Abnormalities observed at the level of gross morphology included size differences in the testes and individuals of mixed sex. These abnormalities were observed in both juveniles and adults. Of the 1,271 frogs collected over two years, mixed sex was observed in eight individuals (0.006%). Testes were sectioned every 7.5 m and stained with hematoxylin and eosin for histological analysis. All sections were examined for gonadal abnormalities, including the incidence of testicular oocytes. Comparisons were made between reference (<0.22 g/L atrazine) and exposed sites in order to determine whether atrazine exposure could be correlated with the incidence of abnormalities. In addition, the incidence of gonadal abnormalities was compared among juvenile and adult frogs to assess potential differences among age classes.
Key words: atrazine, frog, gonad histology