Data from: When parasites disagree: evidence for parasite-induced sabotage of host manipulation

Host manipulation is a common parasite strategy to alter host behavior in a manner to enhance parasite fitness usually by increasing the parasite’s transmission to the next host. In nature, hosts often harbour multiple parasites with agreeing or conflicting interests over host manipulation. Natural selection might drive such parasites to cooperation, compromise or sabotage. Sabotage would occur, if one parasite suppresses the manipulation of another. Experimental studies on the effect of multi-parasite interactions on host manipulation are scarce, clear experimental evidence for sabotage is elusive. We tested the effect of multiple infections on host manipulation using lab bred copepods experimentally infected with the trophically transmitted tapeworm Schistocephalus solidus. This parasite is known to manipulate its host depending on its own developmental stage. Coinfecting parasites with the same aim enhanced each other’s manipulation but only after reaching infectivity. If the coinfecting parasites disagree over host manipulation, the infective parasite wins this conflict: the non-infective one has no effect. The winning (i.e. infective) parasite suppresses the manipulation of its non-infective competitor. This presents conclusive experimental evidence for both cooperation in and sabotage of host manipulation and hence a proof of principal that one parasite can alter and even neutralize manipulation by another.宿主操纵是寄生虫的一类经典生存策略：通过提升寄生虫向后续宿主的传播效率，改变宿主行为以增强自身进化适合度。自然环境中，宿主往往会被多种寄生虫侵染，这些寄生虫在宿主操纵的目标上可能存在一致或冲突的利益诉求。自然选择可能会驱使这类寄生虫走向合作、妥协或破坏行为：当某一寄生虫抑制另一寄生虫的宿主操纵行为时，便会发生破坏现象。目前针对多寄生虫交互对宿主操纵影响的实验研究较为匮乏，相关破坏效应的明确实验证据也难以获取。本研究以实验室繁育的桡足类动物为实验宿主，通过人工侵染营营养传播的硬体裂头绦虫（Schistocephalus solidus），探究多重侵染对宿主操纵行为的影响。已知该寄生虫会根据自身发育阶段调控宿主行为。携带相同操纵目标的共侵染寄生虫，仅在发育至具有侵染性阶段后，才会相互促进彼此的宿主操纵行为。若共侵染的寄生虫在宿主操纵目标上存在分歧，则具有侵染性的寄生虫将主导这场冲突，无侵染性的寄生虫不会产生任何影响。占据主导地位（即具有侵染性）的寄生虫会抑制其无侵染性竞争者的宿主操纵行为。本研究为宿主操纵行为中的合作与破坏效应均提供了确凿的实验证据，同时从原理上证明了一种寄生虫可以改变甚至抵消另一种寄生虫的宿主操纵行为。