Effect of short‐ and long‐term hypophysectomy on the ovary and interrenal of catfish, Heteropneustes fossilis (Bloch)

Catfish were hypophysectomized during the late prespawning period when the ovaries are enlarged with yolky oocytes, and autopsied at close intervals to ascertain the short‐term effects of hypophysectomy. A significant reduction in the ovarian weight occurs between day 4 and day 6 post‐hypophysectomy. Thereafter, the ovarian weight declines rapidly and the lowest value is attained by day 35 post‐hypophysectomy. Hypophysectomy induces atresia of yolk‐laden oocytes and the sequence of changes in an atretic oocyte involves the coalescence of yolk plateletes, breakdown of vitelline membrane, hypertrophy of granulosa cells which quickly phagocytose the yolk, and the eventual merger of masses of granulosa cells in the ovarian stroma. Hydration of the ovaries gradually increases following hypophysectomy and the maximum value is attained by day 19 post‐hypophysectomy when follicular atresia is greatest, and returns to normal by day 49. Hydration of muscles remains almost constant despite hypophysectomy. In the interrenals, the post‐hypophysectomy changes involve leucocytic infiltration, gradual reduction in the nuclear diameter of cortical cells and condensation of chromatin. In the long‐term study, catfish were hypophysectomized during the preparatory period when the ovaries are regressed, and autopsied one and two years post‐hypophysectomy. The ovarian histology of catfish sampled one and two years following hypophysectomy was similar to that of their respective controls inasmuch as sampling was also done in the preparatory period, whereas the interrenal histology was markedly different from that of the controls. In the interrenals of hypophysectomized groups, leucocytic infiltration was more in evidence and the cortical cell nuclear diameter showed significant reduction.