Response of the pituitary of the catfish, Heteropneustes fossilis (Bloch), to bilateral ovariectomy.

Hypophyseal response to bilateral ovariectomy was studied in the catfish, Heteropneustes fossilis, during the prespawning (May) and the spawning (July) periods. During the prespawning period, a significant increase in the number of granulated PAS-positive basophils in the proximal pars distalis of the castrates was recorded on day 45 post-ovariectomy; thereafter a gradual degranulation of basophils was observed. However, in the spawning period a dramatic increase in the number of granulated basophils of the castrates was seen on day 8 post-ovariectomy and the number decreased thereafter. This differential response of the hypophysis to ovariectomy is discussed.