Nematomorph parasites drive energy flow through a riparian ecosystem

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寄生者（ハリガネムシ類）が駆動する渓畔生態系のエネルギー流の解明.京都大学プレスリリース.2011-04-13.Parasites are ubiquitous in natural systems and ecosystem-level effects shouldbe proportional to the amount of biomass or energy flow altered by the parasites. Here wequantified the extent to which a manipulative parasite altered the flow of energy through aforest-stream ecosystem. In a Japanese headwater stream, camel crickets and grasshoppers(Orthoptera) were 20 times more likely to enter a stream if infected by a nematomorphparasite (Gordionus spp.), corroborating evidence that nematomorphs manipulate their hoststo seek water where the parasites emerge as free-living adults. Endangered Japanese trout(Salvelinus leucomaenis japonicus) readily ate these infected orthopterans, which due to theirabundance, accounted for 60% of the annual energy intake of the trout population. Troutgrew fastest in the fall, when nematomorphs were driving energy-rich orthopterans into thestream. When infected orthopterans were available, trout did not eat benthic invertebrates inproportion to their abundance, leading to the potential for cascading, indirect effects throughthe forest-stream ecosystem. These results provide the first quantitative evidence that amanipulative parasite can dramatically alter the flow of energy through and across ecosystems.