Fitness and virulence of a bacterial endoparasite in an environmentally stressed crustacean host
Fitness and virulence of a bacterial endoparasite in an environmentally stressed crustacean host
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DOI：
10.1017/s0031182010000995
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发表时间：
2011-01-01
期刊：
影响因子：
2.4
通讯作者：
De Meester, Luc
中科院分区：
文献类型：
--
作者：
Coors, Anja;De Meester, Luc
宿主与寄生虫的相互作用是由寄生虫毒力、传播成功以及宿主抵抗和恢复的共同进化军备竞赛决定的。寄生虫的毒力和适应性可能取决于宿主条件，例如宿主能量限制。在这里，我们研究了捕食威胁和环境污染物施加的压力在多大程度上影响宿主与寄生虫的相互作用。我们用杀菌细菌体内寄生虫巴斯德氏菌（Pasteuria ramosa）挑战甲壳类动物宿主大型溞，同时将宿主暴露于鱼类利他素、杀虫剂西维因或两种应激源。虽然寄生虫的毒力（以对宿主死亡率和绝育的影响来衡量）在短期接触农药后显着增加，但它并没有受到捕食威胁的影响。以产生的传播阶段来衡量，寄生虫的适应性在鱼类和杀虫剂处理中均有所下降。在捕食威胁下，这种效应比西维因暴露要强得多，并且归因于宿主体细胞生长的减少，可能导致寄生虫发育的资源减少。虽然两种应激源对孢子负荷的间接影响为宿主条件依赖性寄生虫适应性提供了证据，但仅在西维因暴露下毒力增加的发现表明，与无毒鱼类利它素的作用相比，神经毒性化学物质具有更强的生理影响。
Host-parasite interactions are shaped by the co-evolutionary arms race of parasite virulence, transmission success as well as host resistance and recovery. The virulence and fitness of parasites may depend on host condition, which is mediated, for instance, by host energy constraints. Here, we investigated to what extent stress imposed by predation threat and environmental pollutants influences host-parasite interactions. We challenged the crustacean host Daphnia magna with the sterilizing bacterial endoparasite Pasteuria ramosa and simultaneously exposed the host to fish kairomones, the pesticide carbaryl or both stressors. While parasite virulence, measured as impact on host mortality and sterilization, increased markedly after short-term pesticide exposure, it was not influenced by predation threat. Parasite fitness, measured in terms of produced transmission stages, decreased both in fish and pesticide treatments. This effect was much stronger under predation threat than carbaryl exposure, and was attributable to reduced somatic growth of the host, presumably resulting in fewer resources for parasite development. While the indirect impact of both stressors on spore loads provides evidence for host condition-dependent parasite fitness, the finding of increased virulence only under carbaryl exposure indicates a stronger physiological impact of the neurotoxic chemical compared with the effect of a non-toxic fish kairomone.