摘要
取75尾网箱养殖的2～3龄雌性赤点石斑鱼,分为3组(高、低剂量组和对照组),各25尾。高剂量组埋植促黄体生成素释放激素类似物(LHRHA)缓释剂,剂量为300μg/kg体重,低剂量组为100μg/kg体重,对照组埋植不含LHRHA的药丸。分别在实验开始和埋植药丸后0、10、20、30、40天抽血,用放射免疫测定血清类固醇激素(E2、T);解剖鱼体测定相关指标,计算性腺成熟系数;取性腺和肝脏组织常规组织学切片并透射电镜观察。埋植后第10—30天,两种剂量处理组的排卵率均高于对照组,高剂量组显著高于低剂量组。在第10天性腺成熟系数高剂量组为1.055%,卵母细胞已有部分迅速发育到Ⅳ期末(核偏位);低剂量组相对缓慢。第20天性腺成熟系数高剂量组达1.858%,低剂量组为0.987%;处理组卵母细胞基本发育成熟。埋植后第10天,两处理组血清E2和T水平显著升高;第20天显著下降;此后E2保持在较低的水平,T显著低于对照组水平。超微结构的观察证实脑垂体GTH细胞在LHRHA缓释剂诱导性腺发育成熟和排卵过程中处于活跃的合成与分泌状态。LHRHA缓释剂能有效诱导赤点石斑鱼卵巢发育成熟和排卵,而性类固醇激素(E2、T)只与卵黄生成有关,与排卵无关。
Seventy-five female red-spotted grouper （Epinephelus akaara ） of 2 -3 years old were divided into three groups [control group （C）, high （H） and low dose group （L）, 25 fish per group]. Each group was treated as follows：high dose group [300μg luteinizing-hormone releasing-hormone analogue （LHRH-A）/kg body weight], low dose group （100μg LHRH-A/kg body weight） and control （no LHRH-A）. Blood samples were collected on day 0, 10, 20, 30 and 40 after implantation and serum estradiol-17β （E2） and testosterone （T） were determined by radioimmunoassay （RIA）. The fish were killed and the gonads were removed and weighed for calculation of the gonadosomatic index （GSI）. The microstructure and uhrastructure of ovary, liver and pituitary were examined by both light microscope and transmission electron microscope. The results showed that the ovulation rate in the LHRH-A implantation group was significantly higher than that in the control group; that the ovulation rate of the high dose group was significantly higher than that in low dose group. The GSI was 1.055% and migrated nucleus was observed on day 10 in high dose group, ovary developed slowly in low dose group. The GSI reached a high of 1.858% and a low of 0.987% at day 20 in the mature ovary in the LHRH-A implanted group. Serum T and E2 increased significantly after the LHRH-A implantation at day 10 and declined significantly at day 20. Serum T was significantly lower than the control group. Hypertrophied GTH cells, distinct degranulation and marked dilatation of cisternase of the rough endoplasmic reticulum suggest the release of hormone from the GTH cells. These results suggested that sustained administration of LHRH-A significantly induced ovarian maturation and ovulation in the red-spotted grouper. Sex steroid hormone is correlated with vitellogenesis, not ovulation.
基金
国家海洋863项目(2001AA621010)
国家自然科学基金项目(39970586)
广东省科技计划项目(A30502012003C20308)
教育部科学技术研究重点资助项目(02150)
