The deleterious effects of fungicides and herbicides on Xenopus laevis embryos.

Groups of 30 Xenopus laevis embryos, at "tail-bud" stage (Nieukoop-Faber stages 22-24) were exposed to 0.1-2 ppm concentrations of various pesticides for 1 to 10 days. The pesticides used were chloranil and dichlone (both are fungicidal and herbicidal); diquat (herbicide); and nabam (fungicide). The parameters examined were mortality, gross morphology, histology, and behavior. Chloranil (1.25 to 1.75 ppm) treated embryos showed abnormalities of the otolith, optic cup, and general pigmentation. Their movement was sporadically convulsive and they were unable to maintain proper balance. Dichlone (0.1 to 0.15 ppm) disrupted the development of the cephalic end of the embryo. Many of these embryos developed a slightly retarded trunk and tail only. These headless embryos lived for a time and were relatively lethargic. Diquat (0.75 to 2.0 ppm) administration reduced body size and pigmentation, and altered body shape. When embryos were treated with both 1.0 ppm of diquat and 2.0 ppm of nabam the integrity of myomeres and myocommata of the musculature was disrupted. The histological bases of these morphological and behavioral changes are discussed.