EFFECT OF Y-ORGAN ABLATION ON OOCYTE GROWTH IN THE TERRESTRIAL ISOPOD, ARMADILLIDIUM VULGARE

¹ Laboratory of Biology, Kanagawa Prefectural College, Nakaocho 50-1, Asahiku, Yokohama, Kanagawa 241, Japan

The reproductive and molting cycles of the isopod, Armadillidium vulgare, are synchronous during its breeding season. It was found that the rapid growth of oocytes occurs at stage D of the molting cycle. In hibernating females, the oocytes ceased to grow if their Y-organs were surgically extirpated at stage C in early spring. In these animals, many oocytes devoid of follicle cells degenerated along the inner margin of the ovary. Occasionally, however, a mass of granular substance was also seen in that part of the ovary. These results suggest that in A. vulgare the rapid growth of oocytes in stage D females is closely associated with activity of the Y-organ.