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的标准和按长度和年龄划分的成熟率。根据最晚期卵母细胞的发育阶段、排卵后卵泡的出现和闭锁的发生，组织学上将卵巢成熟度分为6类。全年从捕获的雄性和雌性日本沙丁鱼身上采集性腺和血液样本。血清性腺激素水平的变化与年度性腺周期的关系在两性中进行了检查。根据性腺组织学。每年的性腺周期可分为四个时期。血清性腺激素水平的变化与每年的性腺周期相关。在圈养条件下，雌鱼不能成熟和自发产卵，尽管卵母细胞发育到卵黄细胞生长结束。本文研究了几种甾体激素对沙丁鱼卵泡封闭卵母细胞成熟的影响。被发现是最有效的催熟剂。这表明卵黄发生后卵母细胞。圈养的日本沙丁鱼有能力对适当的激素效应作出反应，随后恢复选择性成熟。在目前的研究中。用促黄体激素释放激素类似物（LHRH-&）和人绒毛膜促性腺激素联合诱导日本沙丁鱼卵黄细胞成熟和排卵成功。排卵后卵泡的组织学特征和排卵后残余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。卵巢闭锁女性的状态因子较无闭锁女性低。卵母细胞直径的频率分布呈多模态分布，最先进的卵母细胞群在进入迁移核期时与发育中的卵母细胞群分离。批量繁殖力（BF）表示为BF=1.68 × 10^<-10>BL^<6.19>，其中BL=体长（ne）。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