METHYLMERCURY EFFECTS ON Mytilus galloprovincialis HAEMOCYTES ACTIVITY

Abstract

Bivalves, filter-feeding organisms, due to their wide distri-bution, are used by many countries in biomonitoring, particu-larly in the assessment of xenobiotics in the marine ecosystem.These sentinel organisms are able to accumulate trace metalsand other substances in their tissues. Haemocytes are effectorsof cellular immunity in bivalves and are capable of respond-ing to stressors through activities such as phagocytosis or cyto-toxicity. In order to identify cellular markers to investigate pol-lution, the effect of different concentrations of organic mercury(CH3HgCl) on the morphology and responses of Mytilus gal-loprovincialishaemocytes was studied in this work. Sublethalconcentrations of methylmercury, as evidenced by the Trypanblue exclusion test, were used to investigate its effect on mor-phology, the efficiency of phagocytosis towards yeast cells,the maintenance of the lysosomal membrane and the ability torelease cytotoxic molecules. Alterations in haemocyte viabili-ty, morphological changes and alterations in the cytoskeletonwere observed. The spreading ability, a cell morphometricparameter, was also used as an additional method. Exposureto CH3HgCl influenced the percentage and index of phagocy-tosis. Finally, cytoskeletal and morphological modificationslead to a reduction in the ability to adhere to the substrate andincorporate the target. The cytotoxic activity of M. gallo-provincialis haemocytes towards erythrocytes and the activityrevealed from lysis plaque assay has not been modified byadequate concentrations of methylmercury in the medium. Inaddition, membrane permeability could be affected bymethylmercury due to the reduced retention capacity of neu-tral red by the cells. This evidence confirms that theMediterranean mussel M. galloprovincialisis a suitable modelorganism in the study of the state of health of the marine envi-ronment and in particular for investigation of pollution causedby xenobiotics.