高温诱导对尼罗罗非鱼性别分化及生长的影响

摘要

采用自雌鱼口腔中取出受精卵人工孵化的方法建立了尼罗罗非鱼家系20个.受精后9d,将各家系鱼苗分成两份,分别在28℃(对照组)和36℃(高温诱导组)下养殖,诱导处理12 d后,统计高温诱导期成活率并将实验鱼转入自然水温下培育,养殖60～120 d后对各实验组的雄性率及生长情况进行测定.结果表明,高温处理对仔鱼的成活率没有影响,但能显著提高某些家系的雄性率,如F27(诱导组88％,对照组49％)、F37(诱导组90％,对照组53％)和F41(诱导组91％,对照组53％)；高温处理后多数家系的雄性率略有升高,但不显著；有两个家系高温诱导组雄性率低于对照组,分别是F8(诱导组43％,对照组46％)和F35(诱导组29％,对照组38％),这显示了尼罗罗非鱼性别分化受遗传和环境因子共同作用.生长情况测定结果表明,高温诱导对发育初期罗非鱼的生长没有显著影响.本研究结果说明,高温处理能显著提高某些家系的雄性率,高温诱导和家系选择有望成为高雄性率尼罗罗非鱼新品种培育的新的技术手段.%The Nile tilapia Oreochromis niloticus is a species of great commercial interest in the world. Although various approaches have been introduced to improve productivity,difference in growth between male and female fish is still the major bottleneck for tilapia cultivation. Therefore, high-frequency or all male stocks are preferred to enhance overall productivity of Nile tilapia. In order to investigate the effect of high-temperature treatment on the sex differentiation in Nile tilapia and screen high and low frequency families of males, 20 families were established for Nile tilapia "Ji-Fu" strain. During the reproductive season of Nile tilapia, the 2~3 year-old Nile tilapia females and males were cultivated in 10 m3 pond. The female mouth was checked to see whether there were fertilized eggs or not every 5 - 7 days. If there were fertilized eggs, the eggs were taken out, cultivated in a single tank, and named as a family. Fry were counted at 9 d post-fertilization and the every batch of offspring was divided into two groups: control group and high-temperature group. The control group was maintained at a constant 28°C water temperature, and the high-temperature group at 36°C. Treatment durations were 12 d, and at the end of the treatment, the number of fish in each group was recounted. Treated fry were gradually adapted to 28°C, and then all the fry was transferred into tanks in natural water temperature. Progenies were subjected to sexing at ages of 2 to 4 months. Sexing was conducted by observing the morphology of goriadal cell under microscope. The mortality of fry in control group and high-temperature group was not significantly different. Among 20 families, the frequency of males in high-temperature group was significantly higher than that in the control group in 3 families, including F2 7 (88% in treated group; 49% in control group), F37(90% in treated group; 53% in control group), and F41(91% in treated group; 53% in control group). The high-temperature treatment did not significantly increase the male frequency of most families. However, the frequency of males in high-temperature group was significantly lower than that in the control group in 2 families: F8 (43% in treated group; 46% in control group) and (29%in treated group; 38% in control group). These results prove the possibility to modify the sexual ratio of Nile tilapia and provide new methodology to breed new strain with high frequency of males.