No abstract

No abstract

The ability of Palaemon elegans Rathke, 1937 to regulate internal concentrations of copper, zinc and cadmium has been investigated over a wide range of external metal concentrations. Total body concentrations of copper and zinc are regulated on exposure to dissolved metal concentrations up to 100 pg 1-' metal. Exposure to higher levels of dissolved copper and zinc produces an increase in the metal concentration of the shrimps. Body concentrations of copper may increase by a factor of at least 5 times but only twice the normal body concentration of zinc could be tolerated by the shrimps. Cadmium concentrations are not regulated, the body concentration of metal being proportional to the external metal concentration.

This study set out to investigate the possible effect of life history strategy on the trace metal biology of crustaceans living in coastal sites contaminated by high availabilities of toxic metals. Amphipods brood their young, parents and offspring staying in the same habitat. Therefore a population of amphipods living in a trace-metal-rich estuary would have been selected over generations for any physiological adaptation reducing the.potentia1 toxic action of the trace metals, such as reduced rates of uptake of metals from solution. Crabs, on the other hand, are dispersed by a planktonic larval phase, the zoea, increasing the probability that the parents of individuals inhabiting a metal-rich estuary would have lived in a remote location not exposed to selection pressure to reduce metal uptake rates. Uptake rates of the dissolved trace metals Zn, Cd and Ag were, therefore, measured in amphipods Orchestia gammarellus and crabs Carcinus maenas and Pachygrapsus marmoratus from coastal sites in Britain and France exposed to &fferent degrees of trace metal enrichment, in order to test 3 hypotheses: (1) the mean metal uptake rates of amphipods and crabs from a metal-rich site would be lower than those of the same crustaceans from a control site; (2) the mean metal uptake rates of amphipods would show a greater reduction from those of control amphipods than would those of equivalent crabs; (3) the mean metal uptake rates of amphipods from metal-rich sites would show smaller coefficients of variation than those of equivalent crabs. In practice the mean metal uptake rates of both amphipods and crabs did not show consistent significant differences between the crustaceans from the metal-rich and control sites Furthermore there was no evidence to conclude that the coefficients of variation of the mean uptake rates of amphipods from the relatively metal-rich sites are lower than those of crabs from the same sltes. It is concluded that the exposure of the crustaceans to raised trace metal availabilities has not been sufficient to select for a reduction in dissolved trace metal uptake rates, even in the case of the in situ populations of amphipods. It is relevant that a suite of physiological mechanisms for the amelioration of the potential toxic effects of trace metals is available to coastal invertebrates, and it remains possible that other physiological processes promoting metal tolerance may be active to differing degrees in crustaceans from metal-rich habitats.

No abstract