Abstract
To examine the maturation process of male devil stinger Inimicus japonicus, histological investigations were performed on the testes of 65 individuals reared in an indoor tank (5 t) under natural conditions from July 2006 to July 2010. The seminal lobule has a lumen and the cysts at various stages of development are distributed on the inside the seminal lobule. During the spawning season, the seminal lobules enlarge and become continuous each other as they are filled with spermatozoa. They are present with cysts of both spermatocyte and spermatid in the testis. This suggests that the testicular structure of devil stinger belongs to the lobule type in which the seminal lobules become continuous during the spawning season and that sperm release occurs several times. Spermatogenesis started from October and spermatogonia increased until next Feburary. Spermatocytes were observed for the first time in March. The testes in the spermiation phase appeared from June to August and all individuals showed the spermiation phase in July. Therefore the spawning period was considered to occur from June through August, peaking in July in reared males.
