THE REPRODUCTIVE CYCLE OF THE VIVIPAROUS TELEOST, NEOTOCA BILINEATA, A MEMBER OF THE FAMILY GOODEIDAE

Abstract

The histological study is based on 25 gonads rang-ing from virgin and non-gravid ovaries through all stages of gestation to an ovary 3 hrs. after the birth of young. The spindle-shaped ovary lies in the mid-dorsal region of the coelom; a median septum divides the gonad into 2 lateral chambers which in turn are filled by an ovigerous fold. The eggs are fertilized while still within the follicle but immediately escape into the ovarian lumen where growth occurs. The ovary increases markedly in size during gestation. The ovigerous folds swell considerably with a con-tained lymph-like fluid which probably serves in a pro-tective, nutrient, and respiratory capacity. The fluid within the folds is depleted during gestation. The internal epithelium of the gonad changes from a flattened layer of cells in the resting ovary to one with tall columnar cells actively secretory during gestation. All elaborated products are discharged into the ovarian lumen before the birth of the young. Two wandering tissue cells also contribute to the spongy nature of the gravid ovary, a unique secretory cell and a tissue granulocyte. These; cells elaborate a nutrient substance for use by the embryos. The vascularity of the gravid ovary is increased by a rich, subepithelial capillary plexus. After the birth of the young, the ovary returns to its normal, resting condition.