Ohba Shin-Ya
Laboratory of Insect Ecology and Laboratory of Evolutionary Ecology, Graduate School of Environmental Science, Okayama University, Tsushima, Okayama 700-8530, Japan.
Environ Entomol. 2009 Jun;38(3):856-60. doi: 10.1603/022.038.0339.
A number of fragmentary reports suggest that the endangered diving beetle Cybister japonicus larvae feed on tadpoles, fish, and aquatic insects. However, no quantitative study on the feeding habits of C. japonicus larvae has been reported. In this study, field observations and rearing experiments were carried out to show the feeding ecology of C. japonicus larvae. Unlike previous commentaries, the first- and second-instar larvae of C. japonicus preyed on insects, mainly Odonata nymphs and Notonecta triguttata, irrespective of prey availability, but did not eat vertebrates such as tadpoles and fish in the field. On the contrary, the third-instar larvae fed on both insects and vertebrates. Rearing experiments showed that the number of Odonata nymphs consumed was significantly more than the number of tadpoles consumed by the first and second instars but third-instar larvae ate both the Odonata nymphs and tadpoles in the tadpole-Odonata nymph mixture experiment. The total body lengths of C. japonicus new adults in the Odonata nymph and tadpole-Odonata nymph mixture treatments were statistically equal. These results suggested that the first- and second-instar larvae of C. japonicus prey mainly on insects and do not eat vertebrate animals (insectivore), whereas the third-instar larvae fed on both insects and vertebrates (generalist).
一些零散的报告表明，濒危的龙虱幼虫以蝌蚪、鱼类和水生昆虫为食。然而，尚未有关于日本龙虱幼虫食性的定量研究报告。在本研究中，通过野外观察和饲养实验来揭示日本龙虱幼虫的食性生态。与之前的评论不同，日本龙虱的一龄和二龄幼虫捕食昆虫，主要是蜻蜓若虫和三点仰蝽，而不论猎物的可获得性如何，但在野外它们并不食用蝌蚪和鱼类等脊椎动物。相反，三龄幼虫既捕食昆虫也捕食脊椎动物。饲养实验表明，一龄和二龄幼虫消耗的蜻蜓若虫数量显著多于消耗的蝌蚪数量，但在蝌蚪 - 蜻蜓若虫混合实验中，三龄幼虫既吃蜻蜓若虫也吃蝌蚪。在蜻蜓若虫处理组和蝌蚪 - 蜻蜓若虫混合处理组中，日本龙虱新成虫的总体长在统计学上是相等的。这些结果表明，日本龙虱的一龄和二龄幼虫主要捕食昆虫，不吃脊椎动物（食虫性），而三龄幼虫既捕食昆虫也捕食脊椎动物（广食性）。
