The occurrence of many parasites and their hosts vary conspicuously by season due to their periodic life history events. Nematomorphs are common parasites in terrestrial‐aquatic ecotones, but it is still unknown how the nematomorphs complete their complex life cycles by using multiple hosts that are potentially seasonally variable. In this study, we examined the life history of a nematomorph (Gordionus sp.) inhabiting a mountain stream in northern Japan by the seasonal survey of their infection on aquatic and terrestrial hosts and laboratory experiments. Adults of Gordionus sp. entered into stream from early June to mid‐July. The laboratory experiment suggested that the newly hatched larvae become infective to intermediate host (aquatic insect larvae) from September to November, depending on the water temperature. The nematomorph larvae infected aquatic insect hosts with diverse emergence phenology, which result in prolonged temporal window for the trophic transmission between aquatic and terrestrial hosts. The common definitive host (Pterostichus thunbergi ) seemed to survive multiple years, which would allow the nematomorph larvae to fully develop within the infected host. Trophically transmitted parasites sometimes track a specific pathway of prey–predator interactions within a food web and thus are sensitive to temporal match–mismatch between intermediate and definitive hosts. Contrary to this, the nematomorphs we studied may benefit from using temporally diverse pathways across aquatic and terrestrial food webs, which may result in maintaining the populations in their seasonal environment.

中文翻译：

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日本北部山区河流中的宿主物候和马毛虫（Nematomorpha，Gordiida）的生活史

由于其周期性的生活史事件，许多寄生虫及其寄主的发生因季节而异。线虫是陆生水生生态交错带中的常见寄生虫，但仍不清楚线虫是如何通过使用可能具有季节性变化的多个宿主来完成其复杂生命周期的。在这项研究中，我们通过对水生和陆生寄主感染的季节性调查和实验室实验，研究了居住在日本北部山区河流的线虫（Gordionus sp。）的生活史。成人的手风琴sp。从6月初到7月中旬开始投放。实验室实验表明，新孵化的幼虫根据水温在9月至11月之间感染中间宿主（水生昆虫幼虫）。线虫幼虫感染的水生昆虫宿主具有不同的出现物候特征，导致水生和陆地宿主之间营养传递的时间窗口延长。常见的最终寄主（Pterostichus thunbergi）似乎可以存活数年，这会使线虫幼虫在受感染的宿主内完全发育。营养性传播的寄生虫有时会跟踪食物网中特定的猎物-捕食者相互作用途径，因此对中间宿主和确定宿主之间的时间匹配-不匹配敏感。与此相反，我们研究的线虫可能受益于跨水生和陆生食物网的时间上不同的途径，这可能导致将种群维持在季节性环境中。