半滑舌鳎卵巢发育的组织学和形态数量特征研究

Study on histological and morphometric characters of gonad development of Cynoglossus semilaevis Günther

中文关键词: 半滑舌鳎  卵巢发育  组织学

英文关键词: Cynoglossus semilaevis Günther  Gonadal development  Histological obervation

中文摘要:

      采用组织学方法系统研究了人工养殖条件下半滑舌鳎亲鱼卵巢的组织发育周年变化特征。结果表明，卵母细胞发育可分为6个时相，卵巢发育分为6期。卵巢不同发育时期都由不同类型的卵母细胞组成，半滑舌鳎为非同步分批多次产卵类型。周年发育过程中，6月龄前的鱼卵巢发育处于第Ⅰ期；9-12月龄卵巢可发育至第Ⅱ期；12月龄半滑舌鳎性腺可发育达到Ⅲ期，并一直保持至24月龄。3龄雌鱼达到性成熟，卵巢可发育至第Ⅳ期；随着水温和光周期的调控，卵巢发育进入成熟期（Ⅴ期），发生水合现象是卵母细胞成熟并准备排卵的信号；产卵结束后卵巢退化至第Ⅵ期，排出的卵母细胞退化吸收，以Ⅲ期卵巢越冬后，卵巢退化至Ⅱ期并持续至下一个繁殖周期。人工养殖条件下，卵巢内存在卵母细胞闭锁现象。性腺周年发育过程中，性腺指数（GSI）在性腺达到成熟期时达到峰值，产卵结束后性腺快速退化，GSI值各月份差异显著（P<0.05），亲鱼性腺重量在卵巢发育成熟过程中一直处于生长状态。亲鱼肝脏指数（HSI）在产卵前7-8月份（性腺达到成熟期前30 d左右）达到最大，表明7~8月份是性腺进行卵子发育、卵黄能量储备的重要时期，亲鱼在产卵前通过积极摄食储备体内能量，肝脏在卵母细胞卵黄积累方面具有重要的生理作用。肥满度（CF）值在繁殖盛期10-11月份达到最大，表现出与GSI类似的变化趋势。

英文摘要:

      The temporal dynamics of oocyte growth and ovary development were examined during a 12-month ovarian maturation cycle in captive Cynoglossus semilaevis Günther using light microscopy method. Results showed that the oocyte growth could be divided into 6 phases and ovary development consisted of 6 periods accordingly. Two or three distinct batches of vitellogenic oocytes were found in Cynoglossus semilaevis Günther ovaries at one development stage, indicating that this species are a non-synchronized multiple batch spawners. The ovaries are in stage I when the fish are less than 6 month old, which only appears once in their whole life．As fish grew, the ovaries enter into stage Ⅱ when they are 9 to 12 months old. The stage Ⅲ which were characterized by cortical alveoli accumulation was attained when the fish were 12-month old and maintained until 24-month old. Deposition of lipids and vitellogenesis began to happen in ovaries of stage Ⅳ when the fish were over 3 years old. The ovaries could be matured (stage Ⅴ) under artificial photothermal control from May to August and fish spawned between September and November. Hydration observed in oocytes indicates that the fish were completely matured for ovulation. After spawning period, the ovaries retrogressed to stage Ⅲ via stage Ⅵ, then continued regressing to stage Ⅱ and was maintained until the next reproductive season. Gonadosomatic index (GSI), hepatosomatic index (HSI) and condition factor (CF) were all found to increase prior to, or during the peak phase of vitellogenic growth corresponding to the gonad development, which are important indices for evaluating the reproductive condition of the parental fish. Cynoglossus semilaevis Günther appear to strategically utilize episodes of high feeding activity to accrue energy reserves early in the reproductive cycle prior to its deployment during periods of rapid ovarian growth. In the developing ovaries (mainly after stage Ⅳ), some post-vitellogenic follicles failed to undergo final maturation, resulting in widespread preovulatory atresia, which may depress the fecundity or be an indicator of capacity of multiple spawns.