Parasites alter the reproductive performance of their hosts, limit their growth, and thereby modify the energy budget of these hosts. Experimental studies and theoretical models suggest that the outcome of the host-parasite interactions could be determined by ecological factors such as food availability levels in the local habitats. Nutrient inputs may affect the host's food resource availability with positive or negative effects on parasite infection rates and tolerance of infection, however this has not been specifically evaluated in natural systems. In this study, we evaluate the effects of parasitism by Proctoeces humboldti on body size, gonadosomatic index (GSI), and metabolic rate (oxygen consumption) of their second intermediate host Fissurella crassa limpets, under contrasting natural conditions of productivity (upwelling center vs upwelling shadow sites). Our results evidenced that parasitized limpets collected from the intertidal habitat influenced by coastal upwelling site showed greater shell length, muscular foot biomass and GSI as compared to non-parasitized limpets collected in the same site, and compared to parasitized and non-parasitized limpets collected from the sites under the influence of upwelling shadow conditions. Oxygen consumption was lower in parasitized limpets collected from the upwelling-influenced site than in the other groups, independent of age, suggesting reduced metabolic stress in infected individuals inhabiting these productive sites. Our results suggest that increased productivity in upwelling sites could mitigate the conflict for resources in the P. humboldti - F. crassa system, influencing where such interaction is found in the continuum between parasitism and mutualism. Since parasitism is ubiquitous in natural systems, and play important roles in ecological and evolutionary processes, it is important to analyze host-parasite interaction across a variety of ecological conditions, especially in biological conservation.

中文翻译：

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寄生虫对匙孔的影响取决于上下文。

寄生虫改变其宿主的生殖性能，限制其生长，从而改变这些宿主的能量收支。实验研究和理论模型表明，宿主-寄生虫相互作用的结果可以由生态因素确定，例如当地栖息地的食物供应水平。营养输入可能会影响寄主的食物资源，从而对寄生虫感染率和感染耐受性产生正面或负面影响，但是尚未在自然系统中进行专门评估。在这项研究中，我们评估了洪堡Proctoeces humboldti寄生对它们的第二个中间寄主Fissurella crassa衣壳的大小，性腺激素指数（GSI）和新陈代谢率（耗氧量）的影响，在生产力相对自然条件下（上升中心与上升阴影点）。我们的结果表明，与在同一地点采集的未寄生虫帽相比，从沿海上升地点影响的潮间带生境收集的寄生虫帽显示出更大的壳长，肌肉脚生物量和GSI。受上升阴影条件影响的站点。从上升流影响位点收集的寄生中的耗氧量低于其他组，而与年龄无关，这表明居住在这些生产位点的受感染个体的代谢压力降低。我们的结果表明，上升流地点的生产力提高可以减轻P. humboldti-F.资源冲突。crassa系统，影响在寄生和共生之间的连续体中发现这种相互作用的位置。由于寄生虫在自然系统中无处不在，并且在生态和进化过程中起着重要作用，因此分析各种生态条件下的宿主－寄生虫相互作用特别是在生物保护中非常重要。