Parasite-induced modification of host behavior increasing transmission to a next host is a common phenomenon. However, field-based studies are rare, and the role of environmental factors in eliciting host behavioral modification is often not considered. We examined the effects of temperature, relative humidity (RH), time of day, date, and an irradiation proxy on behavioral modification of the ant Formica polyctena (Förster, 1850) by the brain-encysting lancet liver fluke Dicrocoelium dendriticum (Rudolphi, 1819). This fluke induces ants to climb and bite to vegetation by the mandibles in a state of temporary tetany. A total of 1264 individual ants expressing the modified behavior were observed over 13 non-consecutive days during one year in the Bidstrup Forests, Denmark. A sub-set of those ants (N = 172) was individually marked to track the attachment and release of infected ants in relation to variation in temperature. Infected ants primarily attached to vegetation early and late in the day, corresponding to low temperature and high RH, presumably coinciding with the grazing activity of potential herbivorous definitive hosts. Temperature was the single most important determinant for the induced phenotypic change. On warm days, infected ants altered between the manipulated and non-manipulated state multiple times, while on cool days, many infected ants remained attached to the vegetation all day. Our results suggest that the temperature sensitivity of the infected ants serves the dual purpose of exposing infected ants to the next host at an opportune time, while protecting them from exposure to high temperatures, which might increase host (and parasite) mortality.

中文翻译：

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吸虫诱导的僵尸蚂蚁行为的表达与温度密切相关

寄生虫引起的宿主行为改变增加了向下一个宿主的传播是一种常见现象。然而，基于现场的研究很少，并且环境因素在引发宿主行为改变中的作用往往未被考虑。我们研究了温度、相对湿度 (RH)、一天中的时间、日期和辐射代理对脑包刺刀肝吸虫树状双腔体吸虫 (Rudolphi, 1819) 对多角蚁 (Förster, 1850) 行为改变的影响。 ）。这种吸虫会诱导蚂蚁在暂时手足抽搐的状态下通过下颌骨攀爬并咬食植物。在丹麦 Bidstrup 森林一年内的 13 个非连续天内，总共观察到了 1264 只表现出改变行为的蚂蚁。这些蚂蚁的一个子集（N = 172）被单独标记，以跟踪受感染蚂蚁的附着和释放与温度变化的关系。受感染的蚂蚁主要在一天的早些时候和晚些时候附着在植被上，对应于低温和高相对湿度，可能与潜在草食性最终宿主的放牧活动相一致。温度是诱导表型变化的最重要的决定因素。在温暖的日子里，受感染的蚂蚁会在操纵和非操纵状态之间多次变化，而在凉爽的日子里，许多受感染的蚂蚁整天都附着在植被上。我们的结果表明，受感染蚂蚁的温度敏感性具有双重目的，即在适当的时间将受感染的蚂蚁暴露给下一个宿主，同时保护它们免受高温的影响，高温可能会增加宿主（和寄生虫）的死亡率。