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The effects of head shape variation on growth and metamorphosis in larval salamander (Hynobius retardatus) were examined by a laboratory experiment and a field experiment. In the laboratory experiment, each larva was fed equal amounts and was prevented from accessing others in both the solitary and group treatments, although chemical cues could be transmitted through water in the group treatment. The relative head width of larvae became larger in the group treatment during the early periods but having a large head width did not finally influence growth rate and days for metamorphosis. In the field experiment, larvae were allowed to contact each other directly in two density conditions. The enlarged relative head width was linked to high growth rate in the high-density treatment but not in the low-density treatment. The larval body size distribution in the high-density condition tended to be smaller, and there was a small proportion of large-sized individuals with a broad head width. Moreover, the small number of large larvae metamorphosed much earlier than the others. The mortality of larvae in high-density conditions was much higher than that in the low-density treatments. This would be a consequence of cannibalism in the high-density condition. From the experimental results obtained, it is argued that for the larvae of H. retardatus having a large head is an adaptive tactic that maximizes fitness, particularly in temporary ponds with an unpredictable environment and in crowded conditions. 相似文献
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东北小鲵中枢神经系统形态学与组织学初步研究 总被引:3,自引:1,他引:3
本文应用脊椎动物神经标本制作法和HE染色法,对东北小鲵中枢神经系统的外部形态和组织学结构进行了初步研究,描述了东北小鲵神经系统形态和组织学结构的特点,并与无尾两栖类和爬行类相对比,探讨了有尾两栖类的进化地位。结果表明:与无尾两栖类(如蛙)相比,东北小鲵中枢神经系统中,大脑半球较小,结构较为原始,小脑结构简单,是两栖类中较为原始的类群。此外,东北小鲵开始具有了臂神经丛和骶神经丛,但没有爬行类的发达,可作为两栖类向爬行类进化的证据之一。 相似文献
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大小等级和大小组合差异对盆养安吉小鲵幼体同种相残率的影响 总被引:3,自引:0,他引:3
用改变安吉小鲵 (Hynobiusamjiensis)幼体大小等级、盆养密度和饵料投放量的实验方法 ,研究这些生态要素对同种相残 (撕咬和吞吃 )的影响 ;同时结合Fuetal (2 0 0 3)的研究 ,比较了大小组合的差异对同种相残的影响。结果表明 ,①大小等级、密度与饵料量均显著地影响幼体的被吞吃率 :较小个体易被较大个体攻击 ;低饵料×高密度水平下 ,3个等级大小幼体的同种相残率都最高。②大小组合的差异显著影响幼体间的同种相残率 :不同大小组合的幼体间被吞吃率均显著大于相同大小组合 ,而被撕咬率反之。这证实了体形大小决定种群同种相残率的理论预测。 相似文献
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应用扫描电镜和透射电镜对挂榜山小鲵(Hynobius guabangshanensis)精子的超微结构进行观察和研究.结果表明:1)挂榜山小鲵的精子形态具有小鲵科精子的共同特征:头部细直、有锥形顶体;颈部短而不明显,尾部细长、有波动膜;2)该种小鲵的精子超微结构具小鲵科物种精子的共同特征,即精子无顶体钩,顶体呈三叶草状,尾部无线粒体,轴纤维粗大呈圆柱状等;3)除精子全长(194.1±7.15μm)在小鲵科物种中属于中等外,挂榜山小鲵和本科其他物种的精子在形态量度学方面差异明显:其头部占全长的比例(22.98%)比其他已知小鲵科的物种都低,尾部占全长的比例(65.79%)比其他小鲵科物种都高. 相似文献
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