Acquired Protection and Production of Immobilization Antibody against Cryptocaryon irritans(Ciliophora, Hymenostomatida) in Mummichog(Fundulus heteroclitus).

Cryptocaryon irritans is a pathogenic ciliate of marine fishes. Heavy infections cause mass mortalities of fishes. Although the occurrences had been known only among ornamental fishes in private or public aquaria1,2), it has been prevailing in cultured food fishes with the growth of mariculture3-5). In Japan, vari ous marine fishes, e.g. red sea bream (Pagurus major), tiger puffer (Takifugu rubripes) and Japanese flounder (Paralichthys olivaceus), cultured in net cages in the sea suffer from C. irritans infections. Despite the increasing occurrence of this epizootic, few methods are available to control it, especially in maricultured food fishes. To transfer net cages to uncontaminated areas near the open sea seems to be the only feasible method for the time being. Recently, the immunological responses of fishes to parasites have been studied by many researchers, aiming to establish mea sures to control parasitic diseases6). It is well established that fishes once infected with the freshwater parasitic ciliate Icthyophthirius multifliis, the life cycle of which is similar to that of C. irritans, acquired immunity against the parasite7,8) . It was demonstrated that immobilizing antibodies were involved in the acquired immunity against I. multifiliis9). However, little is known on the immunological response against C. irritans. Although the presence of acquired protective immunity against C. irritans in thick-lipped mullet (Chelon labrosusc) was ex perimentally demonstrated10), the mechanism of the protection is not clear as yet. The present study was conducted to dem onstrate the presence of acquired immunity of fish against C. irritans and the production of immobilization antibodies in im munized fish, as well.