A comparative study of anti-Perkinsus marinus activity in bivalve sera

摘要

The eastern oyster Crassostrea virginica has been decimated by a protistan parasite Perkinsus marinus; however, other bivalves appear to be more resistant to this pathogen. To better understand the basis for this difference in susceptibility, a comparative study of the activities of anti-P. marinus serum proteins of several bivalve species was carried out. Sera from mussels not known to develop P. marinus disease, Mytilus edulis and Geukensia demissa, contained high anti-P. marinus activity. About25 percent of M. edulis serum samples contained <10 kDa anti-P. marinus peptides; the possibility of seasonal, geographic, or other reasons to explain this variability requires additional study. Anti-P. marinus peptides in G. demissa serum were apparently absent. Measurable anti-P. marinus activity was present in C. virginica and C. gigas sera, but at levels many hundred-fold lower than that of the mussels. The greater P. marinus resistance of C. gigas vs. C. virginica could not be explained by differences in anti-P. marinus activity of their sera. Hemocyte lysates from all the bivalves examined produced marked inhibition of the growth of P. marinus, suggesting that antimicrobial agents may be secreted by hemocytes into the serum. These factors may also participate in intracellular destruction of P. marinus, since the killing ability of the hemocytes of the different species closely mirrored the anti-P. marinus activities of their sera. The data suggest that C. virginica lacks active anti-P. marinus serum agents typical of M. edulis and G. demissa; however. P. marinus resistance of C. gigas seems not to depend upon elevated levels of antimicrobial serum factors.