The effect of selenium on the handling of mercury in the shore crab Carcinus maenas

By means of the radiotracer 203Hg the effects of selenite on accumulation, elimination and tissue distribution of low levels of organic and inorganic mercury in the shore crab Carcinus maenas were investigated. Selenite in food or seawater seemed to prompt C. maenas to eat more food contaminated with organic mercury, but did not consistently alter the assimilation efficiency of organic mercury. However, assimilation of organic mercury was higher from homogenized mussel in gelatinous cubes with added organic mercury, than from mussels exposed to organic mercury in seawater. Elimination of injected inorganic mercury from the haemolymph was initially speeded up by selenite in seawater, whereas elimination of injected organic mercury from the haemolymph seemed to be slowed down initially. Selenite in seawater was found to promote translocation of injected organic mercury to the muscles. Selenite given in the food, but not selenite in the seawater, had the same effect on ingested organic mercury.