Manganese kinetics in the sea star Asterias rubens (L.) exposed via food or water

Abstract

Accumulation and elimination of manganese from contaminated food and seawater in the tissues of the sea star, Asterias rubens, were investigated in the laboratory. Dissolved 54Mn was accumulated linearly with time and the concentration factor reached 19 after 23 days. Pyloric caeca, stomach and tube feet reached concentration factors of 14, 13 and 61, respectively. Tube feet, pyloric caeca and remaining tissues contained approximately 10–20, 5 and 70%, respectively, of the total body burden. 54Mn accumulated from seawater was eliminated according to 1st order kinetics with a half-life of 36 days. Sea stars fed homogenates of Mytilus edulis assimilated 69–83% of the 54Mn ingested. Elimination of 54Mn accumulated from food could be described as a two compartment system, with half of the body burden of 54Mn lost with a half-life of 25 days and the other half with a half-life of 1.8 days. Pyloric caeca, tube feet and remaining tissues contained approximately 30–40, 20–25 and 30%, respectively, of the total body burden of 54Mn accumulated from food. The highest concentration was found in the pyloric caeca. In sea stars exposed to 0.4 mg stable Mn ++ l −1, manganese accumulated linearly with time in the tissues examined, the highest concentrations being reached in the tube feet. At exposure to 1.0 mg Mn ++ l −1, manganese accumulated linearly with time in the stomach, whereas pyloric caeca and tube feet showed saturation kinetics. Sea stars showed no mortality at exposure to 10 and 25 mg Mn ++ l −1. Sea stars exposed to 50, 100 and 200 mg Mn ++ l −1 had median survival times of 72, 18 and 14.4 h, respectively.