ANTIBACTERIAL ACTIVITY IN THE HEMOCYTES OF THE SHORE CRAB, CARCINUS-MAENAS

The presence of antibacterial activity in the haemocytes of the shore crab, Carcinus maenas (L.) (Crustacea: Decapoda), was investigated using a selection of Gram-positive and Gram-negative bacteria from geographically diverse waters. Preliminary investigations into the relationship between this activity and the prophenoloxidase activating system (proPO) were also carried out. Antibacterial activity against both Gram-positive and Gram-negative organisms were found to reside exclusively in the granular haemocytes and eight of the twelve bacteria tested were susceptible to this effect. Additional studies, using Psychrobacter immobilis (= Moraxella sp.), revealed that the factor (or factors) responsible was 90% effective within 60 min and was also heat stable, independent of divalent cations, and non-lytic in character. Although antibacterial activity resides in the same cell population that carries the proPO system, there appears to be no relationship between antibacterial activity and phenoloxidase itself. Other components of the proPO system, however, may be involved.