System and Function of Maturation and Spawning in Japanese Sardine Sardinops Melanostictus, in Captivity and Wild.

研究了野生日本沙丁鱼卵巢成熟度的判断标准和成熟率随长度和年龄的变化规律。根据最高级卵母细胞的发育阶段、排卵后卵泡的出现和闭锁的发生，将卵巢成熟分为6种类型。全年都从圈养的雄性和雌性沙丁鱼身上采集了性腺和血液样本。并检测了性腺类固醇水平的变化与性腺年度周期的关系。以性腺组织学为基础。一年一度的性腺周期可分为四个时期。血清性激素水平的变化与性腺的年度周期相关。在圈养条件下，雌性鱼不会自发成熟和产卵，尽管卵母细胞一直发育到卵黄形成生长结束。在Vit…中研究了几种类固醇对沙丁鱼卵泡封闭卵母细胞成熟的影响。更多的RO，和17α，20β-DP。被发现是最有效的成熟诱导剂。这表明卵黄发生后的卵母细胞。圈养的日本沙丁鱼有能力对适当的激素效应剂做出反应，随后恢复自体成熟。在本研究中。用促黄体生成素释放激素类似物(LHRH-&)与人绒毛膜促性腺激素联合使用，成功地诱导了日本沙丁鱼卵母细胞的成熟和排卵。排卵后卵泡的组织学特征和排卵后残留卵母细胞的发育阶段表明，沙丁鱼在一个产卵季节至少产卵两次。卵巢闭锁的女性与卵巢无闭锁的女性相比，其条件因子得分较低。卵母细胞直径的频率分布呈多峰分布，处于迁移核期的最高级卵母细胞在直径频率分布上与发育中的卵母细胞组分离。分批繁殖力(BF)为BF=1.68x10^&lt；-10&gt；Bl^&lt；6.19&gt；式中，Bl=体长(Ne)。较少

The criteria of ovarian maturity and the maturity rates according to lengths and ages were studied for wild Japanese 'sardines. The maturity of ovary was classified into 6 categories histologically based on the developmental stages of the most advanced oocytes, the occurrence of postovulatory follicles and the occurrence of atresia. Gonad and blood samples were taken throughout the year from captive males and females of the Japanest sardine. and changes in serum levels of gonadal steroids were examined in relation to the annual gonadal cycle In both sexes. On the basis of gonadal histology. the annual gonadal cycle was divisible into four periods. Changes In serum levels of gonadal steroids were correlated with the annual gonadal cycle. Under captive conditions, female fish did not mature and spawn spontaneously, although oocytes developed up to the end of vitellogenic growth. The effects of several steroids on the maturation of follicle-enclosed oocytes of sardine were examined In vit … More ro, and 17alpha, 20beta-DP. was found to be the *ost potent inducer of maturation. This suggests that post-vitellogenic oocytes of. the Japanese sardine in captivity have an ability to respond to an appropriate hormonal effector and subsequently to resume selotic maturation. In the present study. maturation and ovulation were successfully Induced In Japanese sardine with vitellogenic oocytes by us ing luteinizing hormone-releasing hormone analogue (LHRH-&), and In combination with human chorionic gonadotropin. The histological features of postovulatory follicles and the developmental stage of residual oocytes after ovulation suggested that sardine spawned at least twice during a spavnlng season. Females with atretic ovaries shoved low values in condition factor compared with females with no atresia in the ovarlies. Frequency distribution of oocytes diameter showed polymodal, and the most advanced group of oocytes separated from the developing group of oocytes In diameter frequency distribution when they attained the migratory nucleus stage. Batch fecundity (BF) was shown as BF=1.68x 10^<-10>BL^<6.19> where BL= body length (ne). Less