Behavioral manipulation of spiders by parasitoid wasps: natural history and mechanism of action

• Ano de defesa: 2015
• Autor(a) principal: Kloss, hiago Gechel
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Aranhas; Aranhas - Comportamento - Modificação; Parasitismo; Relação hospedeiro parasito; Parasitóides; Cyclosa fililineata; Cyclosa morretes; Polysphincta; Entomologia Agrícola
• Link de acesso: https://locus.ufv.br//handle/123456789/26899

Host-parasite and host-parasitoid relationships are common in nature and present interesting systems for gaining understanding of evolutionary mechanisms. One of the central topics in the ecology of parasitic organisms is transmission between hosts. Parasites often have specific adaptations that increase the likelihood of transmission. One of the most interesting strategies is behavioral manipulation, in which the parasite or parasitoid increases the probability of transmission by changing host behavior. One well-studied example of behavioral manipulation is that of parasitoid wasps in the Polysphinctine clade (Insecta: Hymenoptera), which manipulate spider behavior. The wasp stings a spider causing temporary paralysis, then deposit a single egg on abdomen. After a short period of time the egg then hatches into a larva that feeds on spider hemolymph. During the final stage of parasitoid larval development, the spiders modify web architecture, then the larva kills the spider and pupates in the center of the modified web. The origin and evolution of these interactions are not well understood. This thesis work investigates the natural history of two parasitoid wasp and two spider species, focusing on the adaptive value of behavioral modifications in terms of parasitoid survival and the mechanisms used by parasitoid wasps to induce spider behavioral changes. I used as model systems Cyclosa fililineata and Cyclosa morretes (Araneae: Araneidae), which are parasitized by Polysphincta sp. nr. purcelli and Polysphincta janzeni (Hymenoptera: Ichneumonidae), respectively. In the first chapter, I describe the attack behavior and life cycle of Polysphincta sp. nr. purcelli and Polysphincta janzeni. I assert that this behavior is facilitated by biological characteristics of the host, as has been observed for other species. In the second chapter, I use a manipulative experiment to show that web modification by C. fililineata and C. morretes enhances parasitoid survival, indicating adaptive value of this behavior for Polysphinctine wasps. I also present results from a second manipulative experiment evaluating whether changes in web architecture are caused by reduced nutritional status of spiders (i.e., due to parasite exploitation of host resources). I demonstrated that behavioral modification of parasitized spiders is not the result of food restriction, which I interpret as evidence of a chemical mechanism for spider behavioral changes. In the third chapter, I investigated possible chemical mechanisms and found high levels of ecdysone in parasitized spiders with altered behavior, but not in either parasitized spiders with unaltered behavior or in nonparasitized spiders. Thus, behavioral modification in spiders may occur through activation of mechanisms controlling ecdysis, resulting in construction of modified webs and increased parasitoid survival.