BIOACCUMULATION IN SELECTED TISSUES OF LABORATORY EXPOSED CRAYFISH

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There is an overwhelming evidence in the literature that heavy metals in general and mercury, chromium and copper in particular pose a great hazard to the environment, including man. The human health concern for these metals can hardly be overemphasized. Long term exposure to water and food-chain can ultimately result in bioaccumulation of carcinogenic (chromium) and extremely toxic (mercury and copper) metals in the tissues of crayfish and be passed on to humans who are primary consumers. The two major objectives of this study are: (1) to investigate the bioaccumulative potential of these metals in crayfish tissues (lab. exposed) and those collected in the field, and (2) to assess the acute and chronic toxicities of these metals to crayfish populations. The first objective will be achieved by sublethally exposing the adult crayfish to each metal compound for a period of 12 weeks and analyzing their tissues by AAS to determine their uptake. The same number of crayfish (pre- exposed to each metal for 12 wks) continuously will be transferred to uncontaminated water and the depuration of these metals will be measured similarly for the next 12 wks. Water samples from containers of the depurating crayfish will also be analyzed by AAS to determine the amount of metals released into the uncontaminated water. This will provide us precisely the data for uptake and depuration phases. Crayfish from bayous alongside major highways of Louisiana will be analyzed to determine the whole-body burden of these toxicant. Acute toxicities to juvenile crayfish will be determined through 96-h static bioassays and the establishment of LC50 values. LC0 and LC99 will be determined for adult crayfish, using a computerized probit analysis program, which also gives the upper and lover lethal concentrations. Chronic toxicities will be determined by: (1) sublethally exposing newly-born crayfish (0.8-lcm length) for 16 wks and measuring the growth-rate in comparison to controls, (2) measuring the fecundity of females pre-exposed to sub-lethal concentrations before mating till the eggs are laid, (3) assessing the hatchability of treated vs. untreated, (4) observing any discernible behavioral change during the exposure of growth-period. Additionally the possible teratogenic affects of each metal will be determined by microscopic examination of eggs, embryos and newly hatched Louisiana crayfish. Procambarus clarkii Girard.