ABSTRACT
The early life stages of an animal’s life cycle are the most sensitive to environmental contaminants. Responses of fish embryos and larvae to many metals and metalloids include mortality, as well as morphological, physiological, and biochemical alterations. Developmental toxicity is a broad term, encompassing abnormal development, mortality, growth inhibition, and functional deficiencies during early life stages. The chorion protects the fish embryo from some metals but enhances toxicity to others by acting as an ion exchanger. The enhanced toxicity at lower salinity may be due to greater uptake of water, and, therefore, of the toxicants. Among the most commonly observed end points in toxicity testing for effects of pollutants on fish embryos is successful hatch. The sensitive periods in embryonic development are often around the time of gastrulation when the primary inductive events occur. Many heavy metals have been shown to act specifically by inhibiting certain enzymes, thus interfering with metabolic processes in development.
