de Valdez Megan R Wise
Department of Biology, Colorado State University, Fort Collins, CO 80523-1878, USA.
J Vector Ecol. 2006 Dec;31(2):344-54. doi: 10.3376/1081-1710(2006)31[344:pbaoaa]2.0.co;2.
A wide range of parasites are known to cause behavioral changes in their hosts and parasitized insects are especially amenable to the study of such changes. The majority of studies addressing parasite-induced behavioral alterations have focused on parasites with complex life cycles and the adaptive nature of such changes. Behavioral changes caused by parasitoids, single-host parasites that kill their host upon emergence, have been studied less and the adaptive nature of these changes is likely to be different than those in complex life cycles. I investigated behavioral alterations in Aedes aegypti mosquito larvae infected with parasitoid nematodes (family Mermithidae). I conducted several experiments in which I tested the following hypotheses: 1) Mermithid nematodes induce behavioral changes in mosquito larvae and the changes are density dependent. 2) Different species of mermithid nematodes induce similar changes in mosquito larvae behavior. 3) Behavioral alterations vary with mermithid developmental stage. 4) Mosquito larvae infected with mermithid nematodes behave similarly to uninfected food-deprived mosquito larvae. I found that 4th instar Ae. aegypti infected with Romanomermis culicivorax or Strelkovimermis spiculatus exhibited resting behaviors significantly more often than uninfected controls but that intensity of infection did not affect activity levels. In earlier instars, infected mosquito larvae were more active than uninfected control larvae in some behaviors associated with feeding. There was no significant difference between infected and uninfected food-deprived mosquitoes in nine of the ten behaviors observed. The decrease in activity of late instar Ae. aegypti larvae infected with mermithids may be a parasitoid adaptation that reduces the risk of predation and thus increases host and parasitoid survival. The increase in feeding activity in earlier instars as well as the similarity between uninfected food-deprived and infected Ae. aegypti behavior may indicate that these behaviors are adaptive for the parasitoid, increasing nutritional acquisition for successful parasitoid development.
已知多种寄生虫会导致宿主行为发生变化，而被寄生的昆虫尤其适合用于研究此类变化。大多数关于寄生虫诱导行为改变的研究都集中在具有复杂生命周期的寄生虫以及此类变化的适应性本质上。寄生蜂是一类单宿主寄生虫，羽化时会杀死宿主，由寄生蜂引起的行为变化研究较少，而且这些变化的适应性本质可能与具有复杂生命周期的寄生虫不同。我研究了感染寄生线虫（索线虫科）的埃及伊蚊幼虫的行为改变。我进行了多项实验，检验了以下假设：1）索线虫会诱导蚊子幼虫行为发生变化，且这些变化与密度相关。2）不同种类的索线虫会诱导蚊子幼虫行为发生相似变化。3）行为改变随索线虫发育阶段而变化。4）感染索线虫的蚊子幼虫的行为与未感染且饥饿的蚊子幼虫相似。我发现，感染了食蚊罗索线虫或尖刺斯特勒克线虫的四龄埃及伊蚊比未感染的对照组更频繁地表现出静止行为，但感染强度并未影响活动水平。在更早的龄期，感染的蚊子幼虫在一些与进食相关的行为中比未感染的对照幼虫更活跃。在观察到的十种行为中的九种行为上，感染和未感染且饥饿的蚊子之间没有显著差异。感染索线虫的老龄埃及伊蚊幼虫活动减少可能是一种寄生蜂适应性变化，可降低被捕食的风险，从而提高宿主和寄生蜂的存活率。早期龄期进食活动的增加以及未感染且饥饿的埃及伊蚊与感染的埃及伊蚊行为之间的相似性可能表明，这些行为对寄生蜂具有适应性，可增加营养获取以实现寄生蜂的成功发育。
