Laboratorio de Ecologia Sensorial e Comportamento de Artrópodes LESCA, Universidade de São Paulo, Rua Arlindo Béttio, 1000, Ermelino Matarazzo, São Paulo, SP 03828-000, Brazil.
Zoology (Jena). 2013 Jun;116(3):168-74. doi: 10.1016/j.zool.2012.12.001. Epub 2013 May 11.
Most empirical and theoretical papers on prey-predator interactions are for animals with long-range detection, animals that can detect and react to predators long before these touch the prey. Heavy-bodied and chemically defended harvestmen (Arachnida, Opiliones) are an exception to this general pattern and rely on contact to detect arthropod predators. We examined the interactions between the Brazilian wandering spider Ctenus ornatus with harvestmen (Mischonyx cuspidatus) or control prey (Gryllus sp. and M. cuspidatus immature, both with soft integuments). Considering a prey-predator system in which fleeing from or reacting to a predator at a distance is not possible, we predicted both a high survival value of near-range defense mechanisms and that mortality would be higher in the absence of such defense mechanisms. We also expected the predator to behave differently when interacting with harvestmen or with a control prey without such defense mechanisms. Our results from laboratory experiments partially matched our predictions: First of all, histological sections showed that the integument of adult harvestmen is thicker than that of immature harvestmen and that of crickets. Adult harvestmen were less preyed upon than the control prey; the heavy armature increases the survival rate but the secretions from the scent glands do not. The predator did behave differently when attacking harvestmen compared to crickets. Despite the large size difference between predator and harvestmen, the protection provided by the armature allowed some of the harvestmen to survive encounters without pre-contact detection, thus greatly reducing the reliance on long-range detection to survive encounters with predators. Harvestmen call for theoretical and empirical work on prey-predator interactions that take into account the possibility that prey may not detect the predator before contact is established.
大多数关于猎物-捕食者相互作用的经验和理论论文都是针对具有远程探测能力的动物的，这些动物能够在捕食者触碰到猎物之前很久就探测到并对其做出反应。身体沉重且具有化学防御能力的盲蛛（蛛形纲，盲蛛目）是这种一般模式的例外，它们依靠接触来探测节肢动物捕食者。我们研究了巴西游走蛛 Ctenus ornatus 与盲蛛（Mischonyx cuspidatus）或对照猎物（Gryllus sp. 和 M. cuspidatus 未成熟个体，两者都具有柔软的外骨骼）之间的相互作用。考虑到一个不能从远处逃离或对捕食者做出反应的猎物-捕食者系统，我们预测近距防御机制的生存价值会很高，而且在没有这种防御机制的情况下死亡率会更高。我们还预计，当与盲蛛或没有这种防御机制的对照猎物相互作用时，捕食者的行为会有所不同。我们的实验室实验结果部分符合我们的预测：首先，组织学切片显示，成年盲蛛的外骨骼比未成熟盲蛛和蟋蟀的外骨骼都厚。成年盲蛛比对照猎物被捕食的几率更小；沉重的盔甲增加了存活率，但气味腺的分泌物并没有。与攻击蟋蟀相比，捕食者在攻击盲蛛时的行为确实有所不同。尽管捕食者和盲蛛之间存在体型差异，但盔甲提供的保护使一些盲蛛在没有预先接触探测的情况下能够幸存下来，从而大大减少了对远距离探测来逃避与捕食者相遇的依赖。盲蛛需要理论和经验工作来研究猎物-捕食者相互作用，考虑到猎物在接触建立之前可能无法探测到捕食者的可能性。
