Fish and amphibian embryos--a model system for evaluating teratogenicity

Developmental stages of fish and amphibians were used to evaluate reproductive impairments produced by environmental contaminants. Using static-renewal and flow-through procedures, exposure was initiated at, or soon after, fertilization and maintained through 4 days posthatching. Trace concentrations of many environmental toxicants produced high frequencies of mortality and teratogenesis. When developmental stages of the trout were exposed to inorganic mercury, 10% control-adjusted mortality was observed at 1 microgram/L and frequencies of terata in hatched populations ranged from 8% to 43% for exposure concentrations of 2 to 25 micrograms/L. In similar tests with the narrow-mouthed toad, 45% mortality occurred when mercury was administered at 1 microgram/L; frequencies of teratogenesis ranged from 8% to 17% at exposure concentrations of 1 to 5 micrograms/L; and complete mortality occurred at 7 micrograms/L. Boron-induced teratogenesis in trout ranged from 5% at 1 microgram/L to 51% at higher exposure levels. When catfish embryos were exposed to atrazine at 0.06, 4.8, and 46.7 mg/L, terata appeared in surviving populations at frequencies of 4%, 69%, and 100%, respectively. Fish and amphibian developmental stages constitute simple and effective models for 1) investigating mechanisms of teratogenesis, 2) evaluating the impact of environmental toxicants on aquatic biota, and 3) identifying environmental teratogens which may be of concern to human health.