Takamitsu Ando, Hiroyuki Imai, Seiko Mizuta, Hideyuki Doi, Yo Miyake, Shin-ichi Nakano
Proceedings of the Second Japan-Korea Joint Symposium on Limnology 37 - 43 2005/09
[Peer-reviewed] International conference proceedings
We examined food selectivity on microalgae by aquatic insects in Hiji Steram, Ehime, whose main water source is a eutrophic reservoir, from July to August 2004. Abundance and composition of planktonic and epilithic algae, those of aquatic insects and their gut content were determined, followed by estimation of food selectivity using Chesson's alpha index. One of the dominant species in aquatic insects was the filter feeder <I> Cheumatopsyche </I> spp. (Hydropsychidae) during the study period. For phytoplankton, <I> Coelastrum </I> (Chlorophyceae) and <I> Microcystis </I> spp. (Cyanophyceae) were dominant throughout the study period and in August, respectively. Food selectivity of the insect on <I> Coelastrum </I> was negative, suggesting inedibility of <I> Coelastrum </I> for the insect. Positive food selectivity was detected for <I> Microcystis </I> in July, but, in August, the insect showed negative selectivity on <I> Microcystis </I>. In August, there were positive food selectivities on <I> Pediastrum </I> (Chlorophyceae) and <I> Synedra </I> (Bacillariophyceae), both of which were less dominant at the upper station. Thus, <I> Microcystis </I> is edible but not preferable prey for the insect. These results suggest that <I> Cheumatopsyche </I> spp. graze on <I> Microcystis </I> when there is no other edible prey available, and that the insect show selective grazing on some eukaryotic microalgae such as <I> Pediastrum </I> and <I> Synedra </I>.