Lee Joon Ha, Dillman Adler R, Hallem Elissa A
Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, California, 90095, USA.
Department of Nematology, University of California, Riverside, California, 92521, USA.
BMC Biol. 2016 May 6;14:36. doi: 10.1186/s12915-016-0259-0.
Entomopathogenic nematodes (EPNs) are lethal parasites of insects that are of interest as biocontrol agents for insect pests and disease vectors. Although EPNs have been successfully commercialized for pest control, their efficacy in the field is often inconsistent for reasons that remain elusive. EPN infective juveniles (IJs) actively search for hosts to infect using a diverse array of host-emitted odorants. Here we investigate whether their host-seeking behavior is subject to context-dependent modulation.
We find that EPN IJs exhibit extreme plasticity of olfactory behavior as a function of cultivation temperature. Many odorants that are attractive for IJs grown at lower temperatures are repulsive for IJs grown at higher temperatures and vice versa. Temperature-induced changes in olfactory preferences occur gradually over the course of days to weeks and are reversible. Similar changes in olfactory behavior occur in some EPNs as a function of IJ age. EPNs also show temperature-dependent changes in their host-seeking strategy: IJs cultured at lower temperatures appear to more actively cruise for hosts than IJs cultured at higher temperatures. Furthermore, we find that the skin-penetrating rat parasite Strongyloides ratti also shows temperature-dependent changes in olfactory behavior, demonstrating that such changes occur in mammalian-parasitic nematodes.
IJs are developmentally arrested and long-lived, often surviving in the environment through multiple seasonal temperature changes. Temperature-dependent modulation of behavior may enable IJs to optimize host seeking in response to changing environmental conditions, and may play a previously unrecognized role in shaping the interactions of both beneficial and harmful parasitic nematodes with their hosts.
昆虫病原线虫（EPNs）是昆虫的致命寄生虫，作为害虫和疾病传播媒介的生物防治剂受到关注。尽管EPNs已成功商业化用于害虫防治，但其在田间的效果往往不一致，原因尚不清楚。EPN感染性幼虫（IJs）利用多种宿主释放的气味剂积极寻找宿主进行感染。在这里，我们研究它们的宿主寻找行为是否受到环境依赖性调节。
我们发现EPN IJs的嗅觉行为表现出极大的可塑性，这是培养温度的函数。许多对在较低温度下生长的IJs有吸引力的气味剂，对在较高温度下生长的IJs有排斥作用，反之亦然。温度诱导的嗅觉偏好变化在数天到数周的过程中逐渐发生，并且是可逆的。一些EPNs的嗅觉行为也会随着IJ年龄的变化而发生类似的变化。EPNs在宿主寻找策略上也表现出温度依赖性变化：在较低温度下培养的IJs似乎比在较高温度下培养的IJs更积极地四处寻找宿主。此外，我们发现穿透皮肤的大鼠寄生虫类圆线虫在嗅觉行为上也表现出温度依赖性变化，这表明这种变化也发生在哺乳动物寄生线虫中。
IJs发育停滞且寿命长，常常通过多次季节性温度变化在环境中存活。行为的温度依赖性调节可能使IJs能够根据不断变化的环境条件优化宿主寻找，并且可能在塑造有益和有害寄生线虫与其宿主的相互作用中发挥了以前未被认识到的作用。
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