Four new species of Dactylogyrus Diesing, 1850 are described from the gills of three species of Luciobarbus Heckel collected from various hydrographical basins in northern Morocco: Dactylogyrus scorpius n. sp. from Luciobarbus rifensis Doadrio, Casal-Lopez & Yahyaoui; D. benhoussai n. sp. from L. moulouyensis Pellegrin; and D. varius n. sp. and D. falsiphallus n. sp. from L. maghrebensis Doadrio, Perea & Yahyaoui. The descriptions of the new species are confirmed by molecular data (partial 18S rDNA, ITS1, and partial 28S rDNA sequences). All four species belong to the group of Dactylogyrus species, possessing a cross-shaped ventral bar and a male copulatory organ composed of a loosely coiled copulatory tube and an accessory piece with a capsule-like base and recurved distal portion. Given the high shape variability of the haptoral anchors reported among specimens of D. varius n. sp., three morphological forms within this species (D. varius f. vulgaris, D. varius f. magnus, and D. varius f. dromedarius) are recognised. However, specimens belonging to D. benhoussai n. sp. and D. varius f. vulgaris were morphologically very similar and were discriminated with certainty, only when using molecular data.

BackgroundHost specificity in parasites represents the extent to which a parasite’s distribution is limited to certain host species. Considering host-specific parasites of primarily freshwater fish (such as gill monogeneans), their biogeographical distribution is essentially influenced by both evolutionary and ecological processes. Due to the limited capacity for historical dispersion in freshwater fish, their specific coevolving parasites may, through historical host-parasite associations, at least partially reveal the historical biogeographical routes (or historical contacts) of host species. We used Dactylogyrus spp., parasites specific to cyprinid fish, to infer potential historical contacts between Northwest African and European and Asian cyprinid faunas. Using phylogenetic reconstruction, we investigated the origin(s) of host-specific Dactylogyrus spp. parasitizing Northwest African and Iberian cyprinid species.ResultsIn accordance with hypotheses on the historical biogeography of two cyprinid lineages in Northwest Africa, Barbini (Luciobarbus) and Torini (Carasobarbus), we demonstrated the multiple origins of Northwest African Dactylogyrus. Dactylogyrus spp. of Carasobarbus spp. originated from Asian cyprinids, while Dactylogyrus spp. of Luciobarbus spp. originated from European cyprinids. This indicates the historical Northern route of Dactylogyrus spp. dispersion to Northwest African Luciobarbus species rather than the Southern route, which is currently widely accepted for Luciobarbus. In addition, both Northwest African cyprinid lineages were also colonized by Dactylogyrus marocanus closely related to Dactylogyrus spp. parasitizing African Labeo spp., which suggests a single host switch from African Labeonini to Northwest African Luciobarbus. We also demonstrated the multiple origins of Dactylogyrus spp. parasitizing Iberian Luciobarbus species. One Iberian Dactylogyrus group was phylogenetically closely related to Dactylogyrus of Moroccan Carasobarbus, while the second was related to Dactylogyrus of Moroccan Luciobarbus.ConclusionsOur study confirms the different origins of two Northwest African cyprinid lineages. It suggests several independent historical contacts between European Iberian Luciobarbus and two lineages of Northwest African cyprinids, these contacts associated with host switches of Dactylogyrus parasites.

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Cyprinid fishes are known to harbour highly host-specific gill-associated parasites of Dactylogyrus. High similarity in the morphology of sclerotized structures among Dactylogyrus species, especially those parasitizing congeneric cyprinoids, makes their identification difficult. In this paper, four previously known species of Dactylogyrus are characterized and illustrated under a reliable taxonomic framework integrating morphological and molecular evidence, and their phylogenetic relationships are investigated using molecular data. The species are as follows: D. borjensis from Luciobarbus zayanensis; D. draaensis from Luciobarbus lepineyi; D. ksibii from Luciobarbus ksibi and Luciobarbus rabatensis; and D. marocanus from Carasobarbus fritschii, L. ksibi, L. zayanensis and Pterocapoeta maroccana. Our results revealed intraspecific genetic variability among specimens of D. ksibii collected from two different hosts and geographically distant basins. Phylogenetic reconstruction showed that Dactylogyrus spp. parasitizing Moroccan cyprinids are representatives of three main lineages corresponding to morphological differences and host specificity. Our records of D. marocanus on L. zayanensis and P. maroccana increase the range of available host species i.e.,eight species of four cyprinid genera representing two phylogenetic lineages (i.e., Barbinae and Torinae).