ADAPTATIONS DEVELOPED BY HYDROTHERMAL VENT ORGANISMS TO FACE THE STRESS OF HEAVY-METALS

The levels of several heavy metals within hydrothermal fluids an often higher than those measured in seawater. However, there is an obvious opposition between the abundance of species encountered at hydrotherma l vents and the poverty of the communities found in polluted coastal a reas. Heavy metal resistance is achieved by several species via the de toxication of metals and their bioaccumulation into specific tissues o r organs. The relative permanence of the metal storage depends upon th e nature of the cellular. ligands involved in the detoxication process . Binding with insoluble ligands of high chemical stability allows a l onger storage than the association with soluble ligands as metallo pro teins. Metallothioneins (MTs) are low molecular weight proteins involv ed in heavy metal cellular balance the half-life of which depends upon the associated cations. The variability of trace element levels withi n the organisms collected at various sites along the East pacific Rise is high. This high variability correlates with the spatial and tempor al variability of the hydrothermal vent dynamics. The precipitation of the elements extruding from the vent into the bottom seawater is resp onsible for their bioavailability to the surrounding fauna The bioaccu mulation of heavy metals in the tissues of the giant worm, Riftia pach yptila, is mainly achieved via insoluble compounds. But nevertheless, the levels of metallothioneins in some organs are equal to those obser ved for coastal species known to perform metal detoxication via MT syn thesis.