海産無脊椎動物の生殖腺の成熟に関する研究-VI

Abstract

Seasonal changes in the testis of the lined shore crab, Pachygrapsus crassipes, were examined histologically. The materials were obtained along the beach of Niigata City facing the Japan Sea, and the period of collection extended from April to November, 1969. The process of spermatogenesis was classified roughly into six stages. These are: primary and secondary spermatogonia, primary and secondary spermatocytes, spermatids and spermatozoa. The sperm is aflagellate, consisting of a spherical acrosome that is surrounded by a cup shaped nucleus with radiating processes. The acrosome is derived from the PAS-positive granules found in the cytoplasm of the spermatid during spermiogenesis. Further, the acrosome is provided with a proximal tubule and a structure of distal coronet. In April, the seminiferous tubule contains many residual sperms and a cluster of spermatogenetic cells in their earlier stages, such as secondary spermatogonia and primary spermatocytes. Some of the residual sperms are included in the cytoplasm of the nursing cells that form a simple layer of the columnar epithelium. The testes taken from the materials of May to June are filled with a lot of spermatocytes and spermatids. The highest peak of the testicular activity reaches in late July. Spent testes are found in some individuals obtained in late August, but spermatogenesis still continued to exist in a number of specimens obtained in late September to November, because the recovery phase takes place gradually.