Immunization of cultured juvenile rockfish Sebastes schlegeli against Microcotyle sebastis (Monogenea)

To determine whether immunization with Microcotyle sebastis antigen could i nduce protection against the parasite's establishment, naive juvenile rockf ish were immunized by injection or immersion with whole worm antigen of M. sebastis. The infestation intensities of immunized groups following a chall enge (2 wk after boosting) with 5000 M. sebastis eyed-eggs were significant ly lower than those of control groups, when determined 7 wk postinfection. The fish in the groups boosted with M, sebastis antigen showed stronger pro tection than unboosted groups. The control group injected with FCA only sho wed a significantly smaller number of worms than the control group, which w as immersed in PBS containing seawater. The results strongly suggest that b oth specific and nonspecific immune factors participate in the protection o f rockfish against M. sebastis establishment.