SGER: Characterization of Hermaphroditism in Rana Pipiens

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

Previous laboratory studies showed that the herbicide, atrazine, induced sexual abnormalities in both African clawed frogs (Xenopus laevis) and American leopard frogs (Rana pipiens). Hermaphroditism (animals with both testes and ovaries or testes with developing eggs) was the most severe abnormality observed. Later studies showed that similar abnormalities were found in the wild in populations exposed to atrazine via agricultural runoff. Although the cause-effect hypothesis is supported by laboratory data, it is possible that hermaphroditism occurs naturally and that the correlation with atrazine contamination in the wild may be coincidental. The current study will address the possibility in two ways: 1) Animals from populations in the wild that show hermaphroditism will be reared in the laboratory to determine if hermaphroditism occurs in the absence of exposure to atrazine-contaminated water. Development of animals from these populations will be compared with animals from populations that do not show hermaphroditism in the wild. 2) Animals from populations that do not show hermaphroditism in the wild will be reared in atrazine-contaminated water collected from areas where hermaphroditism was observed in the wild to determine if it will induce hermaphroditism in animals that do not normally show this developmental pattern. The two aims outlined above will determine if hermaphroditism occurs naturally, or is the result of contaminant exposure. These studies are important for several reasons: 1) atrazine is the most common contaminant in ground and drinking water; 2) laboratory studies showed that atrazine is active at levels as low as 0.1 parts per billion, a level that can be exceeded even in rain water; 3) atrazine and other pesticides may be involved in amphibian declines; 4) the proposed endocrine mechanisms by which atrazine affects amphibians have been documented in fish, reptiles, and mammals; 5) the same mechanisms may be responsible for cancers produced in rats by atrazine and observed in humans occupationally exposed to atrazine (breast and prostate cancer).