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      Monogenean fauna of alien tilapias (Cichlidae) in south China Translated title: La faune des Monogènes des tilapias (Cichlidae) introduits en Chine du Sud

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          Tilapias are important aquaculture fishes that have been introduced widely all over the world, often carrying their monogenean parasites with them. An extensive investigation on monogeneans of invasive tilapias was conducted in 19 natural water sources in south China between July 2015 and December 2017. We found nine known species of monogeneans, i.e., Enterogyrus coronatus, E. malmbergi, Cichlidogyrus cirratus, C. halli, C. sclerosus, C. thurstonae, C. tilapiae, Scutogyrus longicornis, Gyrodactylus cichlidarum, and one unknown Gyrodactylus species. In addition to reporting ten new hosts and four new geographical records, we observed new morphological characteristics of these species. Observation on living specimens of Enterogyrus spp. demonstrated that these two species have characteristic opisthaptoral retraction capacities, while the opisthaptor glands were not observed in our specimens of E. coronatus and E. malmbergi. The morphological differences of the accessory piece of the male copulatory complex between C. cirratus and C. mbirizei (character for species differentiation) could result from the observation at different perspectives, which indicates that C. mbirizei is likely a synonym of C. cirratus. A more detailed structure of the sclerotized parts of Cichlidogyrus spp. and S. longicornis were revealed by scanning electron microscopy. As was the case for the monogeneans found on alien tilapias from other geographic regions, the present study confirmed the high potential of these monogeneans to establish populations in new habitats.

          Translated abstract

          Les tilapias sont des poissons importants pour l’aquaculture dans le monde entier, où ils ont été largement introduits, souvent accompagnés de leurs Monogènes parasites. Suite à une étude extensive menée de juillet 2015 à décembre 2017 dans le Sud de la Chine, nous avons retrouvé 9 espèces déjà connues de ces parasites, à savoir Enterogyrus coronatus, E. malmbergi, Cichlidogyrus cirratus, C. halli, C. sclerosus, C. thurstonae, C. tilapiae, Scutogyrus longicornis, Gyrodactylus cichlidarum, plus un Gyrodactylus inconnu. En plus de dix nouveaux hôtes et de quatre nouvelles localités signalés pour ces espèces, nos résultats montrent quelques différences morphologiques avec les descriptions originelles des espèces. Sur les spécimens vivants d’ Enterogyrus l’opisthapteur montre des capacités de rétractation variables, ce qui n’a jamais été décrit chez E. coronatus et E. malmbergi ; ces hapteurs ne présentent pas de glandes. La différence principale entre C. cirratus et C. mbirizei (la forme de l’extrémité de la pièce accessoire de l’organe copulateur) pourrait n’être que le résultat de l’angle avec lequel on l’observe, ce qui pourrait indiquer une synonymie entre ces deux espèces. Des images en microscopie électronique à balayage montrent de nouveaux détails des pièces sclérifiées des espèces de Cichlidogyrus sp. et de S. longicornis. Comme cela a été le cas pour les Monogènes trouvés sur des tilapias introduits dans d’autres régions du monde, la présente étude confirme leur fort potentiel à établir des populations dans de nouveaux habitats.

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          Most cited references 55

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          Parasite spillback: a neglected concept in invasion ecology?

          While there is good evidence linking animal introductions to impacts on native communities via disease emergence, our understanding of how such impacts occur is incomplete. Invasion ecologists have focused on the disease risks to native communities through "spillover" of infectious agents introduced with nonindigenous hosts, while overlooking a potentially more common mechanism of impact, that of "parasite spillback." We hypothesize that parasite spillback could occur when a nonindigenous species is a competent host for a native parasite, with the presence of the additional host increasing disease impacts in native species. Despite its lack of formalization in all recent reviews of the role of parasites in species introductions, aspects of the invasion process actually favor parasite spillback over spillover. We specifically review the animal-parasite literature and show that native species (arthropods, parasitoids, protozoa, and helminths) account for 67% of the parasite fauna of nonindigenous animals from a range of taxonomic groups. We show that nonindigenous species can be highly competent hosts for such parasites and provide evidence that infection by native parasites does spillback from nonindigenous species to native host species, with effects at both the host individual and population scale. We conclude by calling for greater recognition of parasite spillback as a potential threat to native species, discuss possible reasons for its neglect by invasion ecologists, and identify future research directions.
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            Monogeneans of West African Cichlid Fish: Evolution and Cophylogenetic Interactions

            The goals of this paper were to investigate phylogenetic and evolutionary patterns of cichlid fish from West Africa and their Cichlidogyrus and Scutogyrus monogenean parasites, to uncover the presence of host-parasite cospeciation and to assess the level of morphological adaptation in parasites. This required the following steps, each one representing specific objectives of this paper: (1) to build phylogenetic trees for Cichlidogyrus and Scutogyrus species based on ribosomal DNA sequences, (2) to investigate phylogenetic relationships within West African cichlid fish based on the analysis of mitochondrial cytochrome b DNA sequences, (3) to investigate host-parasite cophylogenetic history to gain clues on parasite speciation process, and (4) to investigate the link between the morphology of the attachment apparatus and parasite phylogeny. Phylogenetic analyses supported the monophyletic origin of the Cichlidogyrus/Scutogyrus group, and suggested that Cichlidogyrus is polyphyletic and that Scutogyrus is monophyletic. The phylogeny of Cichlidae supported the separation of mouthbrooders and substrate-brooders and is consistent with the hypothesis that the mouthbrooding behavior of Oreochromis and Sarotherodon evolved from substrate-brooding behavior. The mapping of morphological characters of the haptor onto the parasite phylogenetic tree suggests that the attachment organ has evolved from a very simple form to a more complex one. The cophylogenetic analyses indicated a significant fit between trees using distance-based tests, but no significant cospeciation signal using tree-based tests, suggesting the presence of parasite duplications and host switches on related host species. This shed some light on the diversification process of Cichlidogyrus species parasitizing West African cichlids.
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              Phylogenetic relationships among monogenean gill parasites (Dactylogyridea, Ancyrocephalidae) infesting tilapiine hosts (Cichlidae): systematic and evolutionary implications.

              We studied the systematics of 14 species of monogenean (Ancyrocephalidae) gill parasites from West African tilapiine hosts (Cichlidae) using both morphological and genetic data. With these tools, we were able to: (i) confirm the validity of the previously described morphological parasite species and of the genus Scutogyrus; (ii) propose that some stenoxenous species (i.e., parasite species with more than one host) may be composed of sister species (e.g., Cichlidogyrus tilapiae); (iii) state that the use of the morphology of the haptoral sclerites is more suitable to infer phylogenetic relationships than the morphology of the genitalia (which seems to be more useful to resolve species-level identifications, presumably because of its faster rate of change). These results imply that: (i) the specificity of these monogenean parasites is greater than initially supposed (what were thought to be stenoxenous species may be assemblages of oïoxenous sister species); (ii) related species groups (i.e., "tilapiae," "halli," and "tiberianus") have to be, as genus Scutogyrus, validated within the 54 ancyrocephalid species described from 18 species of tilapiine hosts in West Africa, (iii) the group "tilapiae," due to its morphology and host range, have to be considered as being the most primitive; (iv) the occurrence of lateral transfers and parallel speciation processes are necessary to describe the repartition of the newly described parasite groups on the three host genera studied (Tilapia, Oreochromis, and Sarotherodon).

                Author and article information

                EDP Sciences
                04 February 2019
                : 26
                : ( publisher-idID: parasite/2019/01 )
                [1 ] State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory for Improved Variety Reproduction of Aquatic Economic Animals, and Research Center for Parasitic Organisms, School of Life Sciences, Sun Yat-sen University Guangzhou 510275 China
                [2 ] Laboratory of Parasitology and Ecology, University of Yaoundé I PO Box 812 Yaoundé Cameroon
                [3 ] ISEM, Univ Montpellier, CNRS IRD Montpellier France
                Author notes
                parasite180107 10.1051/parasite/2019003
                © S. Zhang et al., published by EDP Sciences, 2019

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                Page count
                Figures: 10, Tables: 1, Equations: 0, References: 61, Pages: 16
                Research Article


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