Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic; Hasselt University, Centre for Environmental Sciences, Research Group Zoology: Biodiversity & Toxicology, Agoralaan Gebouw D, B-3590 Diepenbeek, Belgium; Laboratory of Biodiversity and Evolutionary Genomics, Department of Biology, KU Leuven, Ch. Deberiotstraat 32, B-3000 Leuven, Belgium.
Institute of Biology, University of Graz, Universitätsplatz 2, A-8010 Graz, Austria.
Int J Parasitol. 2020 Jun;50(6-7):471-486. doi: 10.1016/j.ijpara.2020.02.002. Epub 2020 Apr 8.
Lake Tanganyika, East Africa, is the oldest and deepest African Great Lake and harbours one of the most diverse fish assemblages on earth. Two clupeid fishes, Limnothrissa miodon and Stolothrissa tanganicae, constitute a major part of the total fish catch, making them indispensable for local food security. Parasites have been proposed as indicators of stock structure in highly mobile pelagic hosts. We examined the monogeneans Kapentagyrus limnotrissae and Kapentagyrus tanganicanus (Dactylogyridae) infecting these clupeids to explore the parasites' lake-wide population structure and patterns of demographic history. Samples were collected at seven sites distributed across three sub-basins of the lake. Intraspecific morphological variation of the monogeneans (n = 380) was analysed using morphometrics and geomorphometrics of sclerotised structures. Genetic population structure of both parasite species (n = 246) was assessed based on a 415 bp fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene. Overall, we observed a lack of clear geographical morphological differentiation in both parasites along a north-south axis. This lack of geographical population structure was also reflected by a large proportion of shared haplotypes, and a pattern of seemingly unrestricted gene flow between populations. Significant morphological and genetic differentiation between some populations might reflect temporal differentiation rather than geographical isolation. Overall, the shallow population structure of both species of Kapentagyrus reflects the near-panmictic population structure of both host species as previously reported. Morphological differences related to host species identity of K. tanganicanus were consistent with incipient speciation at the genetic level. Both parasite species experienced a recent demographic expansion, which might be linked to paleohydrological events. Finally, interspecific hybridisation was found in Kapentagyrus, representing the first case in dactylogyrid monogeneans.
东非坦噶尼喀湖是最古老和最深的非洲大湖，拥有地球上最多样化的鱼类组合之一。两种鲱鱼，Limnothrissa miodon 和 Stolothrissa tanganicae，构成了总渔获量的主要部分，对当地粮食安全至关重要。寄生虫被认为是高度洄游性上层鱼类种群结构的指标。我们研究了感染这些鲱鱼的单殖吸虫 Kapentagyrus limnotrissae 和 Kapentagyrus tanganicanus（Dactylogyridae），以探讨寄生虫的全湖种群结构和种群历史模式。样本采集自分布在该湖三个次盆地的七个地点。使用形态计量学和硬骨结构的地理形态计量学分析了单殖吸虫的种内形态变异（n=380）。基于线粒体细胞色素 c 氧化酶亚基 I（COI）基因的 415bp 片段，评估了两种寄生虫的遗传种群结构（n=246）。总的来说，我们在南北轴线上观察到两种寄生虫都没有明显的地理形态分化。这种缺乏地理种群结构也反映在大量共享的单倍型和种群之间似乎不受限制的基因流模式中。一些种群之间的显著形态和遗传分化可能反映了时间上的分化，而不是地理隔离。总的来说，两种 Kapentagyrus 物种的浅种群结构反映了先前报道的两种宿主物种的近乎完全交配种群结构。与 K. tanganicanus 宿主物种身份相关的形态差异与遗传水平上的初生物种形成一致。两种寄生虫物种都经历了最近的种群扩张，这可能与古水文事件有关。最后，在 Kapentagyrus 中发现了种间杂交，这是在 Dactylogyridae 单殖吸虫中首次发现。
