Pollutants as developmental toxicants in aquatic organisms.

Pollutants, by disrupting metabolic processes, can interfere with development, and, at critical periods of development, can act as teratogens. Such interference with normal development can be used as a bioassay. Some screening tests are based on this phenomenon. As teratogens, pollutants are fairly nonspecific. Many different classes may elicit the same developmental responses. Mechanisms of teratogenicity include disruption of mitosis, interference with transcription and translation, metabolic disturbances in energy utilization, and nutritional deficits. These in turn interfere with cell interactions, migration, and growth. In aquatic organisms, environmental conditions can be critical. Interactions of pollutant effects with salinity and with temperature have been reported. Interactions between toxicants have also been studied; both synergism and antagonism have been reported. Most reports of teratogenesis have been qualitative. Quantitation has usually been in the form of percentages of embryos affected, but when severity of effect is indexed, more critical analysis is allowed. When effects of other developmental processes such as growth are analyzed, quantitation is readily achieved. Regeneration is an especially useful model of both differentiation and growth. These two components of regeneration can be separately analyzed. Dose-response relationships are readily apparent. In comparison to mammalian embryos, the use of embryos of many aquatic species for testing toxicants has certain advantages, including lower cost and maintenance and shorter development times. They respond to many of the same teratogens. A special advantage is availability for continual examination during development so that abnormalities can be observed and recorded as they arise.