天然および養成オニオコゼ Inimicus japonicus 雌の成熟 Maturation of Wild and Reared Female Devil Stinger, Inimicus japonicus
新潟県上越地方の沿岸海域で漁獲されたオニオコゼの雌175個体と養成魚59個体について卵巣成熟の周年変化を調べた。産卵期には1つの卵巣内に周辺仁期の未熟な卵母細胞群と発達した卵母細胞群が認められることから, 卵母細胞の発達様式は卵群同期発達型に属し, 多回産卵すると考えられた。成熟度およびGSIの周年変化から産卵期は6月から8月で, 産卵盛期はGSIが最も高い値を示す7月であると推察された。しかし, 天然魚では4月から卵黄形成が始まるのに対し, 養成魚では3月および11月から卵黄形成が認められ天然魚とは異なる生殖周期を示した。また, 本研究における天然魚の成熟年齢は3歳で, 生物学的最小形は全長190mm (127.0g) であると推定された。
To examine the maturation process of female devil stinger <I>Inimicus japonicus</I>, histological investigations were performed on the ovaries of 175 individuals collected from the coastal water of Niigata Prefecture, from December 2002 to November 2004 and of 59 individuals reared in an indoor tank (15t) under natural conditions from June 2003 to May 2004.<BR>During the spawning season, oocytes at the yolk globule stage, oocytes at the final mature stage and postovulatory follicles were observed with immature oocytes at the pen-nucleolus stage in ovaries. This suggests that the devil stinger is a multiple spawner and that the development form of oocytes in ovary belongs to the "group-synchronous oocyte development" type.<BR>Based on the seasonal changes of maturity and gonadosomatic index, the spawning period was considered to occur from June through August, peaking in July in both wild and reared females. In wild female, vitellogenic individuals were found in April, however in reared female they were found in March and November. This shows that the annual reproductive cycle of reared female is different from that of wild female. The minimum size for maturation of wild female used in this study was 190mm in total length, and the maturation was estimated to occur at a 3-year-old wild female.
水産増殖 54(4), 495-503, 2006-12-20