RESPONSES OF SHORE CRABS TO PHYSIOLOGICAL CHALLENGES FOLLOWING EXPOSURE TO SELECTED ENVIRONMENTAL CONTAMINANTS

The major objective of this study was to determine whether sub-lethal effects of contaminant exposure could be detected in crabs subjected t o standardised, environmentally realistic physiological challenges in the laboratory. Heart rate changes, associated with transition from re st to physical exercise, together with osmoregulatory ability were ass essed and used as measures of the physiological competence of crabs fo llowing exposure to various concentrations of copper, arsenite and ben zo[a]pyrene (B[a]P). Increasing concentrations of copper caused a corr esponding increase in the heart rate of both resting crabs and crabs s ubjected to physical stress, suggesting an impairment to one or more o f the processes associated with normal respiratory functioning. Furthe rmore, exposure of crabs to copper was clearly detrimental to osmoregu latory ability, with a concentration of 0.1 mg 1(-1) sufficient to cau se greater reduction in haemolymph osmolality than that recorded for c ontrol animals exposed to similar low salinity conditions. The mean he art rate of crabs exposed to increasing concentrations of arsenite dec reased under both rest and stress conditions, suggesting an impairment to one or more of the control processes associated with cardiac physi ology. Arsenite appeared to have little impact on the osmoregulatory a bility of crabs, even at a concentration of 1 mg 1(-1). No significant impairment of either cardiac performance or osmoregulatory capability was observed in crabs exposed to relatively high doses of B[a]P, lead ing to the conclusion that acute exposure to B[a]P poses little immedi ate toxic threat to the physiological processes controlling heart rate and osmoregulation in adult shore crabs. (C) 1997 Elsevier Science B. V.