Uptake and Fate of Lead in the Common Asteroid Asterias Rubens (Echinodermata)

Lead uptake kinetics in the body compartments of Asterias rubens individuals exposed through sea water to different concentrations (5, 20, 50 µg Pb l-¹) were studied during 30 days. Uptake kinetics were always best described by linear regressions. In every compartment, uptake rate increased significantly with the contaminating concentration. At a given concentration, the uptake rate of the central digestive tract was always significantly higher than that of the other compartments. After short-term exposures (50 µg Pb l-¹, 8 days), fate of accumulated Pb was followed in asteroids kept in non-contaminated water during 20 days. The central digestive tract and the pyloric caeca lost Pb according to an inverse exponential trend and concentrations returned to initial values after 4 to 8 days. Pb concentrations in the body wall decreased linearly. Pb concentrations in the skeleton did not vary significantly. In the gonads, Pb concentrations kept on rising while exogenous Pb was no more supplied. Pb loss from the body wall and the digestive compartments could account for such endogenous source to the gonads. It is suggested that Pb accumulated in the gonads is expulsed later through spawning. According to the parameters of uptake and loss kinetics, the central digestive tract and the skeleton are proposed as complementary temporal bioindicators of Pb contamination.