Ctenodrilus serratus (Polychaeta: Ctenodrilidae) is a truly amphi-Atlantic meiofauna species: evidence from molecular data

Specimens of the meiofaunal polychaete Ctenodrilus serratus from six localities on both sides of the North Atlantic were examined by RAPD-PCR and sequencing of the internal transcribed spacers (ITS1, ITS2) and 5.8S DNA. None of the populations showed any monomorphic diagnostic DNA fragments, but rather had a highly polymorphic band pattern; cluster analyses revealed no site-specific clusters of the specimens investigated. Furthermore, sequences were almost identical in populations off the coasts of Europe and the eastern United States, whereas the Bermuda specimens differed to some extent in ITS2. These results indicate the existence of a common gene pool and demonstrate an amphi-Atlantic distribution pattern of the species. Trans-Atlantic dispersal of individuals, by whatever means, must be inferred.