HEMOCYTE AGGREGATION IN THE OYSTER CRASSOSTREA-GIGAS - IN-VITRO MEASUREMENT AND EXPERIMENTAL MODULATION BY XENOBIOTICS

The hemolymph of aquatic invertebrates is the target of many environme ntal contaminants. Different events of the cellular immune response co nstitute potential models for the development of sensitive bioassays. Here, a new methodology is described to quantify in vitro spontaneous aggregation by Crassostrea gigas hemocytes. Preliminary assays indicat ed that the aggregation index was altered when the cells were incubate d at low or high temperature. The chelator EDTA or the drug caffeine a dded to the medium were powerful inhibitors. The effects of xenobiotic s actually found in polluted marine waters [tributyltin (TBT) and trac e metals] were tested by exposure of either the cells or whole individ uals and appeared as efficient potential inhibitors. A higher sensitiv ity to cadmium than to copper has been revealed. Exposure of individua ls in the laboratory to pesticides or TBT at peak environmental concen trations resulted in moderate changes in hemocyte aggregation, a respo nse that could, however, be enhanced by synergistic effects of these c oncentrations with other contaminants or with physicochemical factors in the field. The alteration of spontaneous hemocyte aggregation is th ought to reflect an impairment of hemocyte functions in homeostasis ke eping and even in internal defense. This simple assay may constitute a n additional tool to experiment the toxic effects of xenobiotics in mo lluscs. (C) 1997 Elsevier Science Inc.