AN AUTORADIOGRAPHIC INVESTIGATION OF THE GONADS OF THE PURPLE SEA URCHIN (STRONGYLOCENTROTUS PURPURATUS)

Abstract

The DNA-synthesizing cells in gonads of the purple sea urchin were labeled with tritiated thymidine and detected with autoradiography. Throughout the portion of the annual reproductive cycle when sperm are being produced, primary spermatocytes labeled with tritiated thymidine differentiate into early spermatids in about 6 days, and spermiogenesis takes approximately 4 additional days. In the germinal epithelium of the ovary, pre-leptotene primary oocytes are labeled with tritiated thymidine. However, during the same annual reproductive cycle, long-term experiments do not reveal the differentiation of labeled pre-leptotene primary oocytes into growing primary oocytes, maturing oocytes or ova. It is likely that the labeled primary oocytes remain small until the following annual reproductive cycle, when they grow and mature into ova.