title: The systematics of Echinorhynchus Zoega in Müller, 1776 (Acanthocephala, Echinorhynchidae) elucidated by nuclear and mitochondrial sequence data from eight European taxa.
abstract: The acanthocephalan genus Echinorhynchus Zoega in Müller, 1776 (sensuYamaguti 1963) is a large and widespread group of parasites of teleost fish and malacostracan crustaceans, distributed from the Arctic to the Antarctic in habitats ranging from freshwaters to the deep-sea. A total of 52 species are currently recognised based on the conventional morphological species concept; however, the true diversity in the genus is masked by cryptic speciation. The considerable diversity within Echinorhynchus is an argument for subdividing the genus if monophyletic groups with supporting morphological characters can be identified. With this objective in mind, partial sequences of two genes with different rates of evolution and patterns of inheritance (nuclear 28S rRNA and mitochondrial cytochrome c oxidase subunit I) were used to infer the phylogenetic relationships among eight taxa of Echinorhynchus. These included representatives of each of three genus group taxa proposed in a controversial revision of the genus based on cement gland pattern, namely Echinorhynchus (sensu stricto), Metechinorhynchus Petrochenko, 1956 and Pseudoechinorhynchus Petrochenko, 1956. These groupings have previously been rejected by some authorities, because the diagnostic character is poorly defined; this study shows that Echinorhynchus (sensu stricto) and Metechinorhynchus are not natural, monophyletic groups. A revision of Echinorhynchus will require tandem molecular phylogenetic and morphological analyses of a larger sample of taxa, but this study has identified two morhological characters that might potentially be used to define new genera. The estimated phylogeny also provides insight into the zoogeographical history of Echinorhynchus spp. We postulate that the ancestral Echinorhynchus had a freshwater origin and the genus subsequently invaded the sea, probably several times. The freshwater taxa of the Echinorhynchusbothniensis Zdzitowiecki & Valtonen, 1987 clade may represent a reinvasion of freshwater by one or more ancestral marine species.
authors.affiliation: Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, United Kingdom.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Wayland
authors.affiliation: Department of Biosciences, P.O. Box 65 (Viikinkaari 1), FIN-00014, University of Helsinki, Helsinki, Finland.
authors.forename: Jouni K
authors.initials: JK
authors.lastname: Vainio
authors.affiliation: Department of Life Sciences, Natural History Museum, London, SW7 5BD, United Kingdom.
authors.forename: David I
authors.initials: DI
authors.lastname: Gibson
authors.affiliation: Institut de Recherche sur la Biologie de l'Insecte, UMR CNRS 7261, Université François Rabelais de Tours, Faculté des Sciences et Techniques, Avenue Monge, Parc Grandmont, 372000, Tours, France.
authors.forename: Elisabeth A
authors.initials: EA
authors.lastname: Herniou
authors.affiliation: Department of Life Sciences, Natural History Museum, London, SW7 5BD, United Kingdom.
authors.forename: D Timothy J
authors.initials: DT
authors.lastname: Littlewood
authors.affiliation: Finnish Museum of Natural History, POB 17, FIN-00014, University of Helsinki, Helsinki, Finland.
authors.forename: Risto
authors.initials: R
authors.lastname: Väinölä
keywords: Acanthocephala; Acanthocephaluslucii; Echinorhynchusbothniensis; Echinorhynchusbrayi; Echinorhynchuscinctulus; Echinorhynchusgadi; Echinorhynchussalmonis; Echinorhynchustruttae; molecular phylogeny; parasite; phylogeny; systematics; taxonomy; zoogeography
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