Bioaccumulation du cuivre chez littorina littorea (L.) (Gastéropode prosobranche): signification physiologique et écologique

Abstract

A study of Littorina littorea (L.) samples, collected in their natural environment of experimentally intoxicated in aquariums, shows copper in four types of cells, as revealed by histochemical reaction on thin sections, X-ray and Raman spectrometries or secondary ion emission analysis. The excretory cells of conjunctive tissue (as defined by Cuénot), are dispersed in the vesicular conjunctive tissue and myocardium, and their general appearance resemble podocytes. In these cells, copper is precipitated in the form of clusters of CuS needles inside the lysosomes. The accumulation of copper sulphide increases with the age of the animals and is independent of the environment. It is interpreted as being result of hemocyanin degradation. The perivascular cells surround the aorta and arteries. Here copper is found inside the sphero-crystals, associated with certain other minerals, principally Mg and Ca. Intoxication by copper ions results in a deposit at the periphery of these sphero-crystals. The “digestive cells” of the hepatopancreas are the third type. Copper in a still non-determined form, though known to be in an unstable state, may be found along the lateral and basal boundaries of these cells. These aspects have been observed only in rare organisms collected from polluted zones. The fourth type of cell is the axial conjunctive cells of renal lamellae. Here copper is present in a dispersed pattern overlying that of the sulphydrilated proteins. Maxima concentrations have been found in animals coming from polluted zones, but an excess of copper ions in the environment has no effect on them. Intoxication by copper sulphate causes branchial lesions. Progressive accumulation of copper sulphide, independent of the environment, makes the Littorina an unreliable biological indicator of pollution by copper.