Studies on the uptake of cadmium by the crab Carcinus maenas in the laboratory. I. Accumulation from seawater and a food source

The crab Carcinus maenas (L.) was exposed to radioactively labelled cadmium dissolved in seawater at concentrations of 0.1, 1 and 10 ppm, the latter concentration being toxic to the crabs (50% mortality after 12.3 days). Net accumulation of cadmium from solution was proportional to the level and time period of cadmium exposure. Total absorbed cadmium levels reached 0.0043 and 0.0412 mg Cd g^-1 dry weight after 40 days exposure to 0.1 and 1 ppm Cd, respectively, and 0.1115 mg Cd g^-1 dry weight after 12.3 days average exposure to 10 ppm Cd. The highest tissue concentration was found in the midgut gland, reaching 0.786 mg Cd g^-1 dry weight after 12.3 days average exposure to 10 ppm Cd. The midgut gland only contained about 10% of the total cadmium absorbed from solution, while the exoskeleton contained the bulk of obsorbed cadmium (59 to 80%) probably passively adsorbed onto the surface. When cadmium was absorbed by the crabs from a food source, the midgut gland contained 16.9% of the total absorbed cadmium whereas the exoskeleton now contained only 22.2%. Ten percent of the cadmium available in the food source (Artemia salina) was accumulated by the crabs. When placed in cadmium-free seawater, crabs that had accumulated cadmium from solution lost 69% of the absorbed cadmium in 10 days, mostly from the exoskeleton which lost 78% of its original absorbed cadmium concentration.