Phagocytic and chemotactic responses of manila and carpet shell clam haemocytes against Vibrio tapetis, the causative agent of brown ring disease

Phagocytic and chemotactic activities of haemocytes from two clam species, Tapes decussatus and T. philippinarum have been studied using bacterial cha llenge. Three strains of Vibrio tapetis, the causative agent of the brown r ing disease affecting these clam species, and one strain of Escherichia col i were used in the study. All extracellular products of the bacterial strai ns were demonstrated to be chemoattractants to clam haemocytes, however, si gnificant differences (P<0.025) in migration indices of haemocytes were obt ained between the E. coli and V. tapetis strains. Phagocytosis by T. decuss atus and T. philippinarum haemocytes is apparently a non-specific process, although affected by the viability of the microorganisms. Soluble haemolymp h proteins are not required for identification of non-self or in the intern alisation process. (C) 1999 Academic Press.