The Effect of Salinity on Cadmium Uptake by the Tissues of the Shore Crab Carcinus Maenas

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Abstract
Cadmium accumulation by the haemolymph, gills and carapace of the shore crab Carcinus maenas (L.) was significantly higher in dilute sea water. This was reflected in the whole-body cadmium concentrations. There was no salinity effect with the hepatopancreas or muscle cadmium concentration. Over a 68-day period, cadmium was steadily accumulated by the carapace, with the salinity effect becoming increasingly apparent. In 50 % sea water the gill cadmium concentration apparently reached a maximum level after about 2 weeks of uptake. This was eventually overtaken by the tissue cadmium concentration in the gills of 100 % s.w. animals. After about 48 days the salinity effect had disappeared and the gill cadmium concentration of both 50% and 100% s.w. animals (in 20μ-mol Cd l−1 = 2.3 mg l−1) remained at approximately 0.3 μ-mol Cd g−1 (= 33.7 mg kg−1) wet weight of tissue. The hepatopancreas cadmium also levelled off at about this concentration although no salinity effect was apparent. When animals loaded with cadmium for a 37-day period were returned to clean sea water, their whole body cadmium concentration fell by about 50 % after 11 days. Losses from carapace and gills were important components of this reduction in cadmium concentration.