The IgM concentration and specific antibody titre of oocyte and egg extracts of Vibrio-immunized red sea bream were successfully measured by an enzyme immunoassay and an ELISA procedure. The concentration of oocytic immunoglobulin was found to increase during the vitellogenesis process. The oocytes as well as the fertilized eggs of the immunized females had antibody titre much higher than that of the control group. On the other hand, no considerable difference in immunoglobulin concentration was found between the eggs obtained from immunized and control mothers. Hence, the comparison of the value of antibody titre per mg IgM estimated for the maternal blood, oocytes and eggs of the same fish showed that common features of immunity exist between the oocytes, eggs and maternal blood. The possible origin of the oocytic and egg IgM was shown to be the maternal blood plasma.

Immunoglobulins in the oocytes, fertilized eggs, and yolk sac larvae of red sea bream were success fully detected by SDS-PAGE and Western blotting, using rabbit antibody against red sea bream blood IgM. Those immunoglobulins appeared structurally identical to the blood IgM of the mother fish, based on the same molecular weight of their H and L chains to those found for the blood IgM, 78 kDa and 26 kDa respectively. Referring to the oocytic immunoglobulin, this appeared in the early stage of vitellogenesis before the spawning season and was also present in reproductively active ovaries during spawning. Those observations indicate that immunoglobulin existing in the mother's blood can be trans ferred to its oocytes and subsequently to eggs and yolk sac larvae in red sea bream.