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Knowledge on the diversity of parasitic flatworms of Western Mediterranean cyprinids is extremely scarce. In the present study, we parasitologically investigated 12 cyprinid species across the Strait of Gibraltar inhabiting watersheds in northwest Africa (Morocco) and Iberia (Portugal and Spain). Taxonomically relevant features of the attachment organ and sequences of the 18S rDNA and ITS regions were used for species delineation and to investigate their phylogenetic relatedness. Among the Gyrodactylus collected from Morocco and Spain, we identified specimens with an unusual T-shaped dorsal bar observed herein for the first time. In contrast, the membranous patch-like structure surrounding the twisted inner roots of hamuli and the median ridge of the ventral bar have been generally observed in Eurasian relatives. Our analyses suggest vicariant speciation of Gyrodactylus across the Strait of Gibraltar. We describe herein G. gibraltarensis sp. nov. from Iberian Luciobarbus graellsii; G. moroccensis sp. nov. from northwest African cyprinids, i.e., L. maghrebensis, L. rabatensis, L. rifensis, L. yahyaouii, and L. zayanensis; and finally, G. pseudomoroccensis sp. nov. from Moroccan L. ksibi, all possessing a new haptoral configuration. The genetic divergence and conservative morphologies in populations of G. moroccensis sp. nov. from five cyprinid species support its ongoing speciation in Northwest Africa. The West Mediterranean lineage was revealed to be monophyletic, with Eurasian species forming a sister group. Morphologically, West Mediterranean Gyrodactylus also appeared to be of Middle Eastern origin. Gyrodactylus spp. possessing an unusual T-shaped dorsal bar have most likely speciated, allowing for the appearance of a haptoral morphology that is restricted to the region across the Strait of Gibraltar. To conclude, viviparous Gyrodactylus reflect parasite speciation across the Strait of Gibraltar and the historical biogeography of cyprinids in the West Mediterranean. Full article

Host-specific parasites exhibit close co-evolutionary associations with their hosts. In the case of fragmented/disjunct host distribution, host-specific parasites may reflect the biogeographical history of regions and/or the role played by contacts of hosts. The present study was focused on Dactylogyrus (Monogenea) species almost exclusively parasitizing cyprinoid fishes. We investigated the phylogenetic relationships between Dactylogyrus parasites of Nearctic cyprinoids (Leuciscidae) and Dactylogyrus parasites of Palearctic cyprinoids and used Dactylogyrus phylogeny to explore the biogeography of fish hosts in Europe and North America. Phylogenetic analyses revealed that two Nearctic clades of Dactylogyrus spp. have different origins. Historical contacts between European and North American leuciscids were accompanied by the host switching of Dactylogyrus species. In the Nearctic region, Dactylogyrus parasites also colonized non-leuciscid fishes. Dactylogyrus spp. of three Nearctic leuciscid clades were included in the phylogenetic reconstruction; only Dactylogyrus spp. of the Plagopterinae had a common origin. Dactylogyrus species did not reflect the phylogenetic relationships among leuciscid clades, suggesting that past co-diversification was overshadowed by colonization events mediated by paleogeographic and climatological changes and extensive drainage reorganization. Host-specific monogeneans serve as a supplementary tool to reveal the historical biogeographical contacts between freshwater fish from the North America and Europe and also contemporary contacts of leuciscids in North America. Full article

Our work shows the efficacy of DNA barcoding for recognizing the early stages of freshwater fish. We collected 3195 larvae and juveniles. Of them, we identified 43 different morphotypes. After DNA barcodes of 350 specimens, we ascertained 7 orders, 12 families, 19 genera, 20 species, and 20 Barcode Index Numbers, corresponding to putative species. For the first time, we reported the presence of the brackish species, Gobiosoma yucatanum in Lake Bacalar. Specimens of the genus Atherinella sp. and Anchoa sp. are possibly new species. Using both methods, morphology, and DNA barcodes, we identified 95% of the total larvae collected (2953 to species, and 78 to genus), and all of them were native. From them, the order Gobiiformes represented 87%. The most abundant species were Lophogobius cyprinoides and Dormitator maculatus, followed by Gobiosoma yucatanum and Ctenobius fasciatus. The Muyil and Chuyanché lagoons have the highest number of species. We present for the first time a short description of Cyprinodon artifrons and Floridichthys polyommus. This information conforms an indispensable baseline for ecological monitoring, to evaluate impacts, and developing management and conservation plans of biodiversity, principally in areas under human pressure such as Sian Ka’an, and Lake Bacalar, where tourism is high and growing in disorder. Full article

Countries of lower Mekong regions are highly alarmed by the spread of fish-borne trematode infections, i.e., small liver flukes and minute intestinal flukes especially in Thailand, Lao People’s Democratic Republic (Lao PDR), Vietnam, Cambodia and Myanmar. Moreover; the incidence of cholangiocarcinoma has also been increasing in the endemic area of liver fluke infections. Only a few reports have been published concerning the fish-borne trematodes infections in the central region of Myanmar. However; there is still a lack of information regarding the status of trematodes infections in second intermediate hosts in the Mekong region of Myanmar. Therefore, we conducted surveillance on the distribution of trematode metacercariae in small cyprinoid fishes collected from the Mekong region of Myanmar. A total of 689 fishes (12 different species of cyprinoid fishes) have been collected and examined by pepsin digestion methods. We discovered four species of fish-borne trematode metacercariae infections, i.e., carcinogenic liver fluke, Opisthorchis viverrini; minute intestinal flukes, Haplorchis taichui; Haplorchis pumilio and Haplorchoides sp. in Tachileik, the Mekong Region of Myanmar. The outcome of this study could be a useful index for the fish-borne zoonotic trematode epidemiology in the Mekong area. Besides, the results of our study contribute to filling the gap of information necessary for the control and prevention of fish-borne trematode zoonotic infections in the Mekong region. Full article