Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada.
Oecologia. 2020 Feb;192(2):311-321. doi: 10.1007/s00442-020-04600-4. Epub 2020 Feb 1.
Prevalence of a parasite may be influenced by age of the habitat (= time available for hosts and parasites to colonize habitats), assemblage composition of host and non-host species, or biotic and abiotic habitat features. For a trophically transmitted parasite, the intermediate host may be consumed by both final hosts and 'dead-end' predators that are incompetent to host the parasite. We tested biotic and abiotic factors that might influence parasite prevalence in a freshwater host-parasite system using a dataset collected from 36 water bodies in the vicinity of Edmonton, Alberta, Canada. In this system, eggs of thorny-headed worms (Acanthocephala: Polymorphus spp.) are eaten by intermediate-host amphipods (Gammarus lacustris Sars), which are then consumed by final vertebrate hosts (certain aquatic birds and muskrats) and various non-host waterbird species. We found that acanthocephalan prevalence in amphipods was positively correlated with waterbody age and with abundance of final-host species. In contrast, abundance of the intermediate host G. lacustris was less important and was negatively correlated with parasite prevalence ('encounter-dilution effect'). Similarly, parasite prevalence showed a marginally significant and negative correlation with abundance of 'dead-end' Gammarus-eating birds. We conclude that in our study system, time available for colonization and abundance of final hosts are more important for parasite prevalence in intermediate hosts than is abundance of intermediate and dead-end hosts.
寄生虫的流行情况可能受到栖息地年龄（=宿主和寄生虫定居栖息地的可用时间）、宿主和非宿主物种组合、生物和非生物栖息地特征的影响。对于营养传播的寄生虫，中间宿主可能被最终宿主和无能力容纳寄生虫的“死胡同”捕食者所消耗。我们使用从加拿大阿尔伯塔省埃德蒙顿附近的 36 个水体收集的数据测试了可能影响淡水宿主-寄生虫系统寄生虫流行情况的生物和非生物因素。在这个系统中，棘头虫（Acanthocephala: Polymorphus spp.）的卵被中间宿主（卤虫）捕食，然后被最终的脊椎动物宿主（某些水鸟和麝鼠）和各种非宿主水鸟物种所消耗。我们发现，棘头虫在卤虫中的流行情况与水体年龄和最终宿主物种的丰度呈正相关。相比之下，中间宿主卤虫的丰度就不那么重要了，并且与寄生虫的流行情况呈负相关（“遭遇稀释效应”）。同样，寄生虫的流行情况与“死胡同”捕食卤虫的鸟类的丰度呈负相关，虽然这种相关性只是略微显著。我们得出的结论是，在我们的研究系统中，对于中间宿主中的寄生虫流行情况而言，可供定殖的时间和最终宿主的丰度比中间宿主和“死胡同”宿主的丰度更为重要。
