Brood-production after Hypophysectomy in the Viviparous Teleost Mollienesia latipinna Le Sueur

Abstract

AMONG the predominantly oviparous teleost fishes the habit of viviparity is widespread, and appears to have arisen repeatedly and independently in various families. Details of viviparity are best known for the cyprinodont family Poeciliidae, which includes several popular aquarium fishes such as the guppy, platyfish and swordtail, but even for this group there is very little known about the physiological specializations involved in gestation, which occurs within the ovarian follicle, and in the birth of the young fish¹. Evidence so far has suggested the involvement of pituitary hormones in these processes², but the essential step of hypophysectomy of pregnant females has not been performed, possibly because of the surgical problems inherent in the small size of these fishes. Recently I have developed a technique for hypophysectomy in the poeciliid Mollienesia latipinna, which permits removal of the pituitary gland with good survival in fish down to about 35 mm. length. The operation will be described in detail in a later paper, and this communication is concerned only with the salient effects of hypophysectomy on brood production in the female.