摄食水平对不同性别食蚊鱼仔幼鱼生长发育的影响

在实验室27℃水温下,研究了少食、中食和饱食三个摄食水平对0至25日龄雌雄食蚊鱼(Gambusia affinis)的生长发育特征和饵料利用效率的影响。26d饲养实验结束后,对试验鱼摄食和生长指标、臀鳍分化、性成熟及饵料转换效率进行分析。结果显示:到臀鳍开始分化时,饱食组雄鱼的累计摄食总能量和生长速度开始小于雌鱼,且随日龄的增加差异加大;随摄食水平的增加,0日龄仔鱼到臀鳍分化和性成熟的时间缩短。至实验结束,各摄食组的雄鱼均形成发育完善的生殖足,性腺都达到成熟状态;而雌鱼性成熟迟于雄鱼,且其性成熟更易受到摄食水平的影响,饱食组只有约50%的个体达到性成熟,少食组的卵母细胞则均处在小生长期。随着摄食水平的增加,雌雄鱼的体长、体重和干物质特定生长率均呈明显上升趋势,而干物质饵料转化效率则呈明显下降趋势;实验结束时,雌鱼的生长指标和干物质饵料转化率均大于雄鱼。以上结果表明,伴随臀鳍的分化,食蚊鱼在摄食、生长、发育、性成熟和应对食物丰度变化上表现出显著的性别差异。  

THE EFFECT OF RATION LEVEL ON GROWTH AND DEVELOPMENT OF MALE AND FEMALE GAMBUSIA AFFINIS DURING LARVAL AND JUVENILE STAGES

The experiment was conducted at 3 ration levels (low-ration, medium-ration and repletion-ration) to investi-gate the effect of ration level on growth and feed utilization of male and female Gambusia affinis from 0 to 25 day post-hatch (DPH). For each ration treatment, the experimental larvae born from same Gambusia affeinis were chosen randomly and assigned to three groups (thirty larvae per group). The larvae were respectively reared in beakers (water volume of 200 mL) at (270.5)℃. Fish were fed twice daily (at 09:00 and 21:00) and lasted for 26 days at different ra-tion levels. Larvae were sampled at selected intervals and the following parameters were analyzed: food intake, growth, anal fin metamorphosis, sexual maturation and feed conversion efficiency. At the satiation ration, the day of anal fin began to metamorphose, the total cumulative energy intake and growth rate in male was initially less than female but increased greatly with age. The duration from 0 day-old larvae to anal metamorphosis and to sex maturation got shorter with ration level increasing. To 25 days, all males from different feeding groups have developed complete gonopodium and have reached maturation, while female sexual maturity developed later than males and sexual maturity of female were more vulnerable to the impact of feeding. Only around 50% of individuals reach sexual maturity for satiation group and oocytes of fish from low ration group were all stayed in small growth stage. With increasing ration level, body length, weight and specific growth rate of dry mass of male and female increased significantly, while feed conversion efficiency decreased. At the end of the experiment, the female grew more rapidly and utilized food more efficiently than the male. Our research showed that with the anal fin metamorphosis, there were remarkable differences of growth, feed utilization, development, sexual maturation and responses to changes in food abundance between female and male Gambusia affinis.