Characterization of gonadotropin-induced oocyte jelly coat from the catfish Heteropneustes fossilis (Bloch)

Abstract

The jelly coat is the gelatinous layer surrounding the oocyte follicles in most aquatic animals, and it helps in fertilization and provides nutrition and protection to developing oocytes and embryos. In Heteropneustes fossilis, the oocyte jelly coat consists of three layers, outer, middle and inner, as inferred from the optical density measurements. Histochemically, the jelly coat showed positive reactions for carbohydrate, lipid, protein, sialic acid and acidic sulfated mucosubstances. Hexosamine and sialic acid are the aminosugars present in the jelly coat. The gonadotropin treatment resulted in swelling up (hydration) of the jelly coat. The administration of gonadotropin (in vivo) increased the hexosamine and sialic acid concentrations of the jelly coat time-dependently. However, in vitro, incubation of the follicles with gonadotropin resulted in decreases in the hexosamine and sialic acid contents. The differences in the dynamics of the aminosugars after the gonadotropin treatment suggested immediate impact of surrounding and internal environment to the follicles.