Kmentová Nikol, Gelnar Milan, Koblmüller Stephan, Vanhove Maarten P M
Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 611 37, Brno, Czech Republic.
Institute of Zoology, University of Graz, Universitätsplatz 2, A-8010, Graz, Austria.
Parasit Vectors. 2016 Aug 3;9(1):426. doi: 10.1186/s13071-016-1696-x.
Lake Tanganyika is the world's second deepest lake. Its diverse cichlid assemblage offers a unique opportunity for studying a deep-water host-parasite model in freshwater. Low host specificity and a broad host range including representatives of the Bathybatini tribe in the only monogenean parasite described from this habitat, Cichlidogyrus casuarinus Pariselle, Muterezi Bukinga & Vanhove, 2015 suggest a link between lower specificity and lower host density. Conversely, high host specificity and species richness are reported for monogeneans of the lake's littoral cichlids. We further investigated whether the deep-water environment in Lake Tanganyika is really monogenean species-depauperate by investigating the monogenean fauna of Trematocara unimaculatum (a representative of the tribe Trematocarini, the sister lineage of the Bathybatini) and Benthochromis horii, a member of the tribe Benthochromini, found in the same deep-water habitat as the already known hosts of C. casuarinus.
Sclerotised structures of the collected monogenean individuals were characterised morphologically using light microscopy and morphometrics.
Both examined cichlid species are infected by a single monogenean species each, which are new to science. They are described as Cichlidogyrus brunnensis n. sp., infecting T. unimaculatum, and Cichlidogyrus attenboroughi n. sp., parasitising on B. horii. Diagnostic characteristics include the distal bifurcation of the accessory piece in C. brunnensis n. sp. and the combination of long auricles and no heel in C. attenboroughi n. sp. In addition C. brunnensis n. sp. does not resemble C. casuarinus, the only species of Cichlidogyrus thus far reported from the Bathybatini. Also Cichlidogyrus attenboroughi n. sp. does not resemble any of the monogenean species documented from the pelagic zone of the lake and is among the few described species of Cichlidogyrus without heel.
As two new and non-resembling Cichlidogyrus species are described from T. unimaculatum and B. horii, colonisation of the deep-water habitat by more than one morphotype of Cichlidogyrus is evident. Based on morphological comparisons with previously described monogenean species, parasite transfers with the littoral zone are possible. Therefore, parasites of pelagic cichlids in the lake do not seem to only mirror host phylogeny and the evolutionary history of this host-parasite system merits further attention.
坦噶尼喀湖是世界第二深湖。其多样的丽鱼组合为研究淡水深水宿主 - 寄生虫模型提供了独特机会。在这个栖息地描述的唯一单殖吸虫寄生虫——卡氏丽体盘虫（Cichlidogyrus casuarinus Pariselle, Muterezi Bukinga & Vanhove, 2015）宿主特异性低且宿主范围广泛，包括巴蒂巴蒂尼部落（Bathybatini）的代表，这表明较低的特异性与较低的宿主密度之间存在联系。相反，据报道该湖沿岸丽鱼的单殖吸虫具有高宿主特异性和物种丰富度。我们通过调查单斑颤丽鱼（Trematocara unimaculatum，颤丽鱼部落（Trematocarini）的代表，巴蒂巴蒂尼的姐妹谱系）和霍氏底栖丽鱼（Benthochromis horii，底栖丽鱼部落（Benthochromini）的成员）的单殖吸虫动物区系，进一步研究坦噶尼喀湖的深水环境是否真的单殖吸虫物种匮乏，这两种鱼与卡氏丽体盘虫已知宿主生活在相同的深水栖息地。
使用光学显微镜和形态测量学对收集的单殖吸虫个体的硬化结构进行形态学表征。
两种被检查的丽鱼物种分别被一种单殖吸虫物种感染，这两种单殖吸虫均为科学上新发现的。它们被描述为布伦氏丽体盘虫（Cichlidogyrus brunnensis n. sp.），感染单斑颤丽鱼；以及阿滕伯勒氏丽体盘虫（Cichlidogyrus attenboroughi n. sp.），寄生于霍氏底栖丽鱼。诊断特征包括布伦氏丽体盘虫新种中辅助片的远端分叉，以及阿滕伯勒氏丽体盘虫新种中长耳叶和无足跟的组合。此外，布伦氏丽体盘虫新种与卡氏丽体盘虫不同，卡氏丽体盘虫是迄今为止从巴蒂巴蒂尼报道的唯一一种丽体盘虫。阿滕伯勒氏丽体盘虫新种也与该湖浮游区记录的任何单殖吸虫物种不同，并且是少数已描述的无足跟的丽体盘虫物种之一。
由于从单斑颤丽鱼和霍氏底栖丽鱼中描述了两种新的且不同的丽体盘虫物种，很明显有不止一种形态类型的丽体盘虫在深水栖息地定殖。基于与先前描述的单殖吸虫物种的形态比较，与沿岸带的寄生虫转移是可能的。因此，该湖浮游丽鱼的寄生虫似乎不仅仅反映宿主系统发育，这个宿主 - 寄生虫系统的进化历史值得进一步关注。
