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Developmental Abnormalities in Free-living Anurans From Agricultural Habitats

Martin Ouellet1, Jean Rodrigue2, Joel Bonin2, Stephane Lair3, and David M. Green1

1Redpath Museum, McGill University, 859 Sherbrooke St. W.,
Montreal, Quebec, H3A 2K6 Canada

2Canadian Wildlife Service, Quebec Region
1141 Route de L'Eglise, P.O. Box 10100, Ste. Foy
Quebec, G1V 4H5 Canada

3Department of Pathology, Ontario Veterinary College
University of Guelph, Guelph
Ontario, N1G 2W1 Canada.


Developmental abnormalities were recorded in wild-caught American toads (Bufo americanus), bullfrogs (Rana catesbeiana), gray treefrogs (Hyla versicolor), green frogs (Rana clamitans), mink frogs (Rana septentrionalis), northern leopard frogs (Rana pipiens), spring peepers (Pseudacris crucifer), and wood frogs (Rana sylvatica) in agricultural habitats of the St. Lawrence River Valley of Quebec, Canada, between 1992 and 1996. Limb deformities were observed in 300 metamorphosing anurans out of 4286 (7.0%) examined in 60 sites exposed to pesticides, compared to 16 of 1075 (1.5%) in 26 control sites. The prevalence of limb deformities among contaminated sites varied from 0 to 67%, and from 0 to 7.7% in control sites. Among adults, 19 out of 732 (2.6%) had limb deformities in 54 pesticide-exposed sites, while 11 of 693 (1.6%) were malformed in 27 controls. Limb deformities included cases of ectromelia, ectrodactyly, polymely, polydactyly, syndactyly, clinodactyly, cutaneous fusion between the femur and tibiofibula, and five other types of limb abnormalities. Of 3655 metamorphosing anurans examined in 1996, we observed 126 cases of limb deformities (34.5ppt), 41 cases of limb and/or digit amputation (11.2ppt), 14 unilateral anophthalmia (3.8ppt), 12 black-eyed frogs (3.3ppt), 12 cases of melanism (3.3ppt), 10 blue frogs (2.7ppt), 8 cases of generalized edema (2.2ppt), 7 cases of eye anomalies (1.9ppt) including 3 ectopic eyes, 3 deformed jaws (0.8ppt), and 2 cases of traumatic enucleation (0.5ppt). Histopathological examination of limb deformities has not yet revealed any etiologic agents. Preliminary statistical analysis (Mann-Whitney U-test, p>0.05) indicates no significant difference in occurrence of limb deformities between pesticide-exposed and control populations. However, the prevalence and diversity of deformities in some of the farmland habitats, their simultaneous occurrence in more than one species at given sites, their overall diversity, and the fact that many agents are potentially harmful to anuran development, emphasize the need for further studies under both field and laboratory conditions.

 

U.S. Department of the Interior
U.S. Geological Survey
Patuxent Wildlife Research Center
Laurel, MD, USA 20708-4038
http://www.pwrc.usgs.gov/naamp3/naamp3.html
Contact: Sam Droege, email: Sam_Droege@usgs.gov
Last Modified: June 2002