Frog Mutations Result From Malathion

Mutations appear during early tadpole stage
at levels as low as 5 part per million

Department of Zoology, University of Poona, India
SOURCE: Bulletin of Environmental Contamination Toxicology, 31:170-176 (1983)

NORMAL TADPOLE 2 DAYS DEVELOPMENT	MALATHION EXPOSED 2 DAYS Tadpole exposed to 5 parts per million of malathion after 2 days. Note beginning formation of downward pointing tail.	MALATHION EXPOSED 4 DAYS Note downward curvature of the tail. Impairments such as this, even though not causing immediate death, will result in increased vulnerability to predators.	SEVERE MUTATIONS 2 DAYS Gross abnormalities appear after 2 days at 10 parts per million of malathion.

The photographs above show the surprising results of a study exposing over 400 tadpoles to different exposure levels of malathion in water. Levels of exposure tested were from 1-20 parts per million (ppm) of malathion in water and a control group which was not exposed to any malathion contaminated water.
In summarizing their work, the researchers stated (pg. 173),

"The results of the present investigation clearly showed malathion is teratogenic (able to cause birth defects) to embryos in the range of 5 to 10 ppm. Beyond 10 ppm it is highly embryotoxic killing embryos within 24 to 48 hours. The abnormalities observed in the frog embryos like curvature body axis, blister formation, poor development and abnormal behavior appeared to be similar to those of fish embryos treated with an organophosphorous insecticide (Kaur and Toor 1977).... Malathion was found to be affecting the survival of the embryos and the rate of mortality was dose dependant.... At a concentration of 1 ppm no mortality or gross morphological abnormality was observed. In few cases loss of balance and abnormal behavior of tadpoles was observed. These tadpoles were swimming either in a circle or showed abnormal twitching of the tail during swimming. Their swimming activity was considerably reduced as compared to controls and some of them remained at the bottom of the petri dish until disturbed."

This article was reported in:
Bulletin of Environmental Contamination Toxicology,31, 170-176 (1983)
and is available on the second floor of the University of South Florida Medical Library

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