Chick, amphibian, and fish embryos were evaluated as bioassay and bioindicator organisms. Test procedures were developed by which embryonic stages may be used 1) in bioassay systems to evaluate the toxicity of particular metallic or metal-containing trace contaminants, and 20 as bioindicators to monitor the quality of natural water resources.
A bioassay technique was devised in which metallic toxicants were administered to chick embryos by "needle tract" injection into the yolk sac. This provided more uniform distribution of test metals throughout the yolk mass than can be obtained by conventional yolk sac injection methods, and gave more sensitivity and uniformity of test results. Metals such as arsenic, cadmium, mercury, lead and zinc are easily detectable at a level of 1 ppb.
An in vitroculture technique was developed by which embryos of aquatic vertebrates may be "maintained" for bioassay and bioindicator purposes. Five test species were identified, suitable synthetic culture water was formulated, and culture monitoring procedures were determined. Most toxic metals (e.g., mercury) may be detected at 1ppb or less with the use of more sensitive embryonic species (e.g., trout). Early cleavage stages of the leopard frog (Rana pipiens) proved more sensitive to cadmium than older embryos, similar to results obtained in Phase I with mercury treatment of frog embryos. Early developmental stages, therefore, have proven especially important for use in bioassay and bioindicator systems.
Supported in part by the Office of Water Research and Technology, U.S. Department of the Interior, as authorized under the Water Resources Research Act of 1964.
Birge, Wesley J.; Westerman, Albert G.; Black, Jeffrey A.; and Roberts, Oliver W., "Sensitivity of Vertebrate Embryos to Heavy Metals as a Criterion of Water Quality, Phase II: Bioassay Procedures Using Developmental Stages as Test Organisms" (1975). KWRRI Research Reports. 206.