ニホンシカＣｅｒｖｕｓ　ｎｉｐｐｏｎ（奈良公園）雄性生殖器官の組織学的研究　　精巣と精巣上体の生後発達と季節的変化について

A histological study was undertaken on a postnatal development and seasonal changes of testis and epididymis of the Japanese deer (Cervus nippon) in Nara Park. Groups and numbers of deer in-cluded in this study are as follows.<BR>1) Neonatal fawn: from birth up to two months old, 9 cases.<BR>2) Immature fawn and yearling: from three months old up to two years old, 7 cases.<BR>3) Adult stag: over two years old, twenty-six cases (one exceptional case, i.e., B558 is included).<BR>Results obtained in this study are as follows.<BR>1. Testis of the neonatal fawn was thin spindle in shape having a long axis less than 1cm in length. Meanwhile, the testis of a yearling was spheroidal in shape 2cm long and 1.2cm wide. The testicular weight and tubular diameter were very variable among neonatal fawns, probably resulting from a release from the intrauterine environment. The diameter of seminiferous tubule of the fawns up to one year old varied between 40μm and 60μm with a few exceptions. The testis weight of yearlings showed an abrupt increase in their second autumn when a tubule attained a level of 90μm in diameter. At the same time, a few yearlings seemed to attain the full spermatogenic activity.<BR>2. The testis of stags in a rutting season was spheroidal in shape having about 5.5cm in length and between 3 and 4cm in width. The weight of the testis also increased remarkably about four times as heavy as that of in non-breeding season. The tubule diameter at a stage of full activity varied between 140μm and 240μm. Afterwards, the tubule decreased in diameter ranging from 100μm to 140μm toward the stage of involution.<BR>3. The rutting season of the deer in Nara Park is thought to be from the middle of October to the middle of December. The testicular recrudescence seemed to begin in June, and both the weight and spermatogenesis attained its full development in August. Concomitantly, the interstitial tissue re-initiated the seasonal differentiation and the development of interstitial cells correlated closely to the development of seminiferous tubules.<BR>4. Corresponding to an abrupt increase in weight of the testis of yearlings in their second au-tumn, the epididymis also showed a remarkable increase in weight. Concomitant with this, the di-ameter of the ductus epididymidis and height of the epithelium also showed a remarkable increase. The weight of epididymis of stags in rutting season attained about two times the weight in a non-breeding season and the diameter of the ductus epididymidis also showed a remarkable increase.<BR>5. In a winter after the rut, spermatozoa persisted in the testis as well as in the epididymis until February, and hence the possibility of delay in successful mating is considered. At present, Japanese deer in Nara Park is not regarded as a true feral population. Beside, an enforced amputa-tion of the hard horn has traditionally been undertaken on some of stags in October. Therefore, it is very doubtful whether the specific hierarchy has been preserved in this population. Accordingly, breeding pattern described in this paper may involve some deviations from their original character-istics.