ENHANCEMENT OF PERKINSUS-MARINUS DISEASE PROGRESSION IN TBT-EXPOSED OYSTERS (CRASSOSTREA-VIRGINICA)

In vitro exposure of Crassostrea virginica hemocytes to tributyltin (T BT) can inhibit antimicrobial defense mechanisms dependent on reactive oxygen intermediates, as measured by chemiluminescence (CL). However, tissue TBT concentrations attained in this in vivo study (similar to 7500 ppb, dry weight) did not inhibit hemocyte recruitment, phagocytos is, CL activity or serum lysozyme. This TBT level was nevertheless eff ective in enhancing progression and lethality of Perkinsus marinus inf ections. Immune stimulation was found to be associated :vith advanced P. marinus infections, as indicated by increased hemocyte recruitment into the circulation and increased CL activity. This played no apparen t role in controlling the infection and was insensitive to TBT. Using this battery of standard assays of defense-related functions, the exac erbation of P. marinus infections by TBT could not be attributed to it s putative immunosuppresive activity. Copyright (C) 1996 Elsevier Scie nce Ltd.