CADMIUM UPTAKE AND DEPURATION BY THE PLEUROCERID GASTROPOD, LEPTOXIS CARINATA (BRUGUIЀRE), AND ITS POTENTIAL USE AS AN INDICATOR SPECIES

Abstract

Similar to other gastropods, Leptoxis carinata displays an ability to accumulate cadmium, followed by very slow elimination of the metal. This pleurocerid was subjected to a series of experiments to determine rates of uptake and depuration of cadmium in this species. Its overall capacity as an indicator species was also analyzed. After 21 days in 10.0 ppb or 50.0 ppb cadmium, rates of uptake were 1.56 μg Cd/g dry tissue/day and 3.53 μg Cd/g dry tissue/day, respectively. Steady-state was not achieved, and after 21 days in artificial pond water, very slow depuration and passive reuptake occurred. L. carinata displays high variability of accumulated cadmium for both concentrations (uptake and depuration), with higher variability at each time point for the Low-Dose group. The general criteria for a good indicator species are: the substance must accumulate without mortality, the organism should be easily sampled and sedentary with a life-span that is long enough for more than one age-class to be sampled, they should be abundant at the collection or study site, large enough for analysis, easily maintained in the laboratory, tolerant of brackish water and they should provide a high bioconcentration factor for the substance in question. As well, a correlation should exist between the concentration in the organism and what is measured in the ambient water, and specimens from different locales should accumulate the toxin similarly. L. carinata met the following criteria: cadmium is not immediately lethal, it is sedentary, has a long life-span, and it is abundant, hardy, and easily sampled. The criteria met suggest a role in monitoring a stream for cadmium contamination. However, more work needs to be done in order to determine its efficacy as an indicator species.