Direct measurement of fight or flight behavior in a beetle reveals individual variation and the influence of parasitism
Direct measurement of fight or flight behavior in a beetle reveals individual variation and the influence of parasitism
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DOI：
10.1371/journal.pone.0216387
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发表时间：
2019-05-22
期刊：
影响因子：
3.7
通讯作者：
Davis, Andrew K.
中科院分区：
文献类型：
--
作者：
Ebot-Ojong, Felicia;Jurado, Elizabeth;Davis, Andrew K.
动物如何以及在多大程度上应对潜在的威胁是一个引人入胜的话题，人们已经对此进行了充分的研究，尤其是在昆虫方面，尽管人们通常不会考虑寄生虫的影响。越来越多的研究表明，即使是良性寄生虫也会对宿主对威胁的生理或行为反应产生积极或消极的影响。考虑到这一点，我们进行了一个实验，使用有角的passalus甲虫，Odontotaenius disjunctus，自然寄生于passali软骨线虫；我们让甲虫进行模拟攻击（类似于竞争对手的战斗或捕食者的攻击），从遭遇的视频中我们量化了一系列行为（触角运动，攻击性姿态，威胁表现等），加上警报呼叫（鸣叫）的频率，这些都对应于“战斗或逃跑”的反应。我们从两次野外采集的140只甲虫中获得了行为和寄生虫的数据，其中一半在我们的实验室中被饲养了三周，条件很紧张（没有洞穴）。在模拟的攻击过程中，我们观察到各种各样的行为，从甲虫几乎没有抵抗到那些极具攻击性的甲虫，尽管大多数甲虫表现出适度的反应。报警率也有所不同，但令人惊讶的是，这些与行为反应的大小无关。同样令人惊讶的是，紧张的住房并没有增强攻击期间的身体抵抗力，但确实提高了报警率。重要的是，被寄生的甲虫对攻击的身体反应明显低于没有被寄生的甲虫（这意味着它们对攻击的抵抗力减弱了）。关于寄生的结果，结合我们实验室之前的工作，表明passali C.线虫抑制了宿主的急性应激或战斗或逃跑反应（可能来自它的能量消耗），这可能使宿主更容易受到它们在应激事件中所应对的危险。
How and to what degree an animal deals with potential threats is a fascinating topic that has been well-researched, particularly in insects, though usually not with the impact of parasites in mind. A growing body of work is showing how even benign parasites can affect, positively or negatively, their hosts' physiological or behavioral reaction to threats. With this in mind we conducted an experiment using horned passalus beetles, Odontotaenius disjunctus that were naturally parasitized with a nematode Chondronema passali; we subjected beetles to simulated attacks (resembling rival fighting or predator attacks) and from videos of the encounters we quantified a suite of behaviors (antennae movement, aggressive posturing, threat displays, etc.), plus rates of alarm calls (stridulations) which all correspond to the "fight or flight" reaction. We obtained behavioral and parasite data from 140 beetles from two field collections, of which half had been housed in our lab for three weeks in conditions that would be stressful (little cover for burrowing). We observed a wide range of behaviors during the simulated attack procedure, from beetles offering little resistance to those which were extremely aggressive, though most beetles showed a moderate reaction. Alarm calling rates also varied, but surprisingly, these were not correlated with the magnitude of behavioral reactions. Also surprising was that stressful housing did not heighten the physical resistance during attacks, but did elevate alarm calling rate. Importantly, parasitized beetles had significantly reduced physical reactions to attack than those without nematodes (meaning their resistance to the attack was muted). The results concerning parasitism, coupled with prior work in our lab, indicate that the C. passali nematode depresses the hosts' acute stress, or fight or flight, reaction (likely from its energetic cost), which may make hosts more susceptible to the very dangers that they are coping with during the stress events.