密度对大树蛙蝌蚪生长发育和存活率的影响

种群密度效应主要表现在影响和调节种群的死亡率、发育速率、繁殖率以及扩散、迁移等反应种群数量动态的重要参数。分析密度对大树蛙蝌蚪生长发育和存活率的影响,有助于探究外界环境因子导致大树蛙种群密度迅速下降的作用机制。设置了15、20、25只/L和30只/L 4个密度组,测量大树蛙蝌蚪的尾长、体长、发育时间和存活率。结果表明,在15—30只/L范围内,密度升高显著降低了大树蛙蝌蚪尾长和体长的生长速率,减小其变态期的尾长和体长大小,其中与15只/L相比,20、25只/L和30只/L 3组蝌蚪的尾长分别降低了11.6%、11.8%和13.9%,体长分别降低了11.1%、9.5%和12.9%;随着密度的升高,大树蛙蝌蚪发育至跗蹠部伸长期和前肢伸出期的所需时间显著延长;大树蛙蝌蚪生长后期的存活率随密度升高显著降低,但密度对蝌蚪生长早期的存活率影响不显著。因此,密度升高可显著减小大树蛙蝌蚪的尾长和体长、延长发育时间和降低其生长后期的存活率,可能影响大树蛙蝌蚪变态后的适合度。

The effect of rearing density on the development and survival of Rhacophorus dennysi tadpoles

The population density of amphibians can greatly influence the dynamics of these populations by changing several key population parameters, such as mortality, development, reproductive rate, and dispersal and migration, especially in the larval stage. Meanwhile population density may change dramatically due to changes in the environment,, thus affecting the development and survival rate of the larval stage. Therefore, studying the impact of population density on larval growth and survival may help to understand the mechanism of rapid amphibian population declining caused by environmental factors. Nonetheless, the effect of population density on amphibian larvae is very poorly understood. In this study, we conducted laboratory simulation experiments to investigate the effect of rearing density on the development and survival of Rhacophorus dennysi tadpoles. We measured the tail length, snout-vent length, development time, and survival rate of Rhacophorus dennysi tadpoles at four rearing density levels (15, 20, 25 and 30 ind/L) and significant differences in tadpole performance were observed between density levels -tadpoles reared at higher densities were significantly smaller at metamorphosis, had longer larval development time and lower larval survival at later stage compared to those reared at the lowest density. Compared to tadpoles reared at the 15 level, tadpoles reared at 20, 25 and 30 density levels was 11.6%, 11.8% and 13.9% less in tail length, respectively, and 11.1%, 9.5% and 12.9% less in snout-vent length, respectively. In addition, increased rearing densities had also significantly prolonged the development time of tadpoles and lowered the survival rate at later stages, although they did not affect the early survival of the tadpoles.