DIURNAL SPERMATOGENESIS AND SPAWNING IN THE SECONDARY MALE OF A PROTOGYNOUS WRASSE, PSEUDOLABRUS-JAPONICUS (TELEOSTEI, LABRIDAE)

The bambooleaf wrasse, Pseudolabrus japonicus, exhibits diandric proto gyny, and the secondary male performs pair spawning with a female who enters his territory. We examined diurnal spermatogenesis and spawning in the secondary male of a protogynous wrasse. In captivity, a single secondary male spawned daily over one month between 06:00 and 09:00 f rom October to November. Number of B-type spermatogonia and spermatocy tes showed the lowest level at 00:00, increased gradually thereafter, peaked at 15:00, and decreased rapidly from 21:00 to 00:00. Spermatid number did not change significantly throughout the day. The number of spermatozoa increased gradually from 18:00, reached a maximum at 06:00 , just prior to spawning, and thereafter decreased markedly at 09:00, after spawning. These results clearly showed that spermatogonial proli feration and meiosis occurred between 00:00 and 15:00, and spermiation occurred between 18:00 and 06:00. Thus, the secondary male of bambool eaf wrasse exhibits a diurnal rhythm of spermatogenesis and spermiatio n.