ENVIRONMENTAL CONTAMINANTS INFLUENCING IMMUNE FUNCTION IN MARINE BIVALVE MOLLUSKS

The increased observation of pollution induced disease conditions in m arine organisms has led to a growing interest on the effects of enviro nmental contaminants on the immune system. Most studies on modulation of the immune system in bivalves by pollutants have concentrated on th e effects of heavy metals and polycyclic aromatic hydrocarbons (PAHs). The current literature on contaminant effects on specific components of the bivalve immune system is reviewed together with the effects on susceptibility to infection. Data are presented showing the effects on immune parameters of exposure to Vibrio tubiashi following pre-exposu re to copper or cadmium. Mussels exposed to cadmium for 7 days followe d by 7 days exposure to V. tubiashi demonstrated significantly higher numbers of circulating haemocytes compared with non-Vibrio-exposed gro ups. Similar experiments conducted with copper exposure for both 7 day s and 7 weeks followed by V. tubiashi for 7 days demonstrated a signif icant decrease in the percentage of circulating eosinophils compared w ith basophilic cells for both short and long term exposures. The intra cellular release of superoxide (NET reduction) by haemocytes was stimu lated in Vibrio-challenged mussels with no copper pre-exposure but was significantly reduced in mussels pre-exposed to 0.2 ppm of copper for 7 weeks. The mortalities for the copper experiments showed increased levels with increasing copper concentration and were consistently high er in the V. tubiashi challenged mussels which had also been exposed t o copper. (C) 1995 Academic Press Limited