Deep-water parasite diversity in Lake Tanganyika: description of two new monogenean species from benthopelagic cichlid fishes

Abstract

BackgroundLake 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.MethodsSclerotised structures of the collected monogenean individuals were characterised morphologically using light microscopy and morphometrics.ResultsBoth 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.ConclusionsAs 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.

Underexplored diversity of gill monogeneans in cichlids from Lake Tanganyika: eight new species of Cichlidogyrus Paperna, 1960 (Monogenea: Dactylogyridae) from the northern basin of the lake, with remarks on the vagina and the heel of the male copulatory organ

“…Cichlidogyrus milangelnari n. sp. belongs to the group of species with short hook pairs I-IV, VI and VII (sensu Vignon et al [ 21 ]), a copulatory tube without a swollen proximal portion and non-sclerotized vagina (see [ 37 ]), just like C. attenboroughi Kmentová, Gelnar, Koblmüller & Vanhove, 2016 [ 16 ]; C . banyankimbonai Pariselle & Vanhove, 2015 [ 17 ]; C. berminensis Pariselle, Bitja Nyom & Bilong Bilong, 2013 [ 38 ]; C .…”

“…banyankimbonai Pariselle & Vanhove, 2015 [ 17 ]; C. berminensis Pariselle, Bitja Nyom & Bilong Bilong, 2013 [ 38 ]; C . bifurcatus Paperna, 1960 [ 24 ]; C. brunnensis Kmentová, Gelnar, Koblmüller & Vanhove, 2016 [ 16 ]; C. buescheri Pariselle & Vanhove, 2015 [ 15 ]; C. consobrini Jorissen, Pariselle & Vanhove, 2017 [ 39 ]; C . fontanai Pariselle & Euzet, 1997 [ 40 ]; C. frankwillemsi Pariselle & Vanhove, 2015 [ 17 ]; C. franswittei Pariselle & Vanhove, 2015 [ 17 ]; C. georgesmertensi Pariselle & Vanhove, 2015 [ 17 ]; C .…”

“…from only 20 cichlid hosts [ 14 ]. At least six cichlid tribes were never investigated for monogeneans [ 15 , 16 ]. The distribution of the gill monogeneans in Tanganyikan cichlids may provide additional evidence for the interrelationships among cichlid species [ 10 , 17 ].…”

“…All species of Cichlidogyrus described until now from Tanganyikan cichlid hosts possess a heel (e.g. [ 14 , 28 ]) except for Cichlidogyrus attenboroughi Kmentová, Gelnar, Koblmüller & Vanhove, 2016 from Benthochromis horii Takahashi, 2008 (Benthochromini) which was described recently [ 16 ].…”

“…in littoral cichlid fish communities of Lake Tanganyika in Burundi. Only scarce reports on these flatworms exist from this stretch of the lakeshore [ 10 , 13 , 16 ]. Investigation of five Tanganyikan hosts of three different tribes, i.e.…”