Mar Biol (2010) 157:69–80 DOI 10.1007/s00227-009-1296-9 123 ORIGINAL PAPER Eurythoe complanata (Polychaeta: Amphinomidae), the ‘cosmopolitan’ Wreworm, consists of at least three cryptic species Romulo Barroso · Michelle Klautau · Antonio M. Solé-Cava · Paulo C. Paiva Received: 19 January 2009 / Accepted: 30 August 2009 / Published online: 17 September 2009 © Springer-Verlag 2009 Abstract Eurythoe complanata (Pallas 1766) has been considered a cosmopolitan species with a great morpholog- ical similarity across its geographic range. To elucidate whether E. complanata is actually a single species, genetic (cytochrome oxidase subunit I and allozymes) and morpho- logical diVerences were compared among specimens from the PaciWc, Caribbean, and South Atlantic Oceans. Large levels of COI divergence (10–22%) and diagnostic allo- zyme loci identiWed three cryptic species: one in the eastern PaciWc and two in the Atlantic, with one being morphologi- cally diVerentiated and found only in islands. COI sequences between PaciWc and Atlantic lineages were much more divergent than those of other transisthmian inverte- brates, indicating their split before the Panama Isthmus closure or a faster evolutionary rate of COI for this species. The existence of two Atlantic species may be a conse- quence of parapatric speciation followed by a secondary invasion or even a sympatric speciation in the Atlantic oce- anic islands. Introduction Phenotypic distinctiveness has been the operational basis of polychaete taxonomy for a long time, primarily based on microscopic observations (Westheide and Schmidt 2003). As with many other marine taxa, this approach has led to the worldwide “lumping” of many morphologically similar, yet evolutionary distinct, species (Klautau et al. 1999; Pfenninger and Schwenk 2007), often resulting in the inXa- tion of assumed geographic distributions (Knowlton 1993; Thorpe and Solé-Cava 1994). In last decade, a number of molecular studies revealed several cryptic species of polychaetes within diVerent gen- era, such as Perinereis from the English channel and the Mediterranean (Scaps et al. 2000), Syllis from the Mediter- ranean (Maltagliati et al. 2000), Dipolydora from the Sea of Japan (Manchenko and Radashevsky 2002), Neanthes and Hediste from the Northern Hemisphere (Breton et al. 2003), Ophelina from the Mediterranean (Maltagliati et al. 2004), and Pectinaria and Owenia from the Northeast Atlantic (Jolly et al. 2006). Atlantic and PaciWc populations have been genetically compared for Palola, Streblospio, and Polydora (Schulze 2006; Schulze et al. 2000; Rice et al. 2008, respectively). In all cases, cryptic species were found, raising doubts on the existence of truly conspeciWc populations on both sides of the Americas. Generally, levels of interspecies gene divergence were much higher than those observed between conspeciWc populations (e.g. Schulze et al. 2000), demonstrating the taxonomic Communicated by J. P. Grassle. Electronic supplementary material The online version of this article (doi:10.1007/s00227-009-1296-9) contains supplementary material, which is available to authorized users. R. Barroso · P. C. Paiva (&) Instituto de Biologia, Departamento de Zoologia, Laboratório de Polychaeta, Universidade Federal do Rio de Janeiro, IB, CCS, Bl. A, Ilha do Fundão, Rio de Janeiro, RJ 21941-590, Brazil e-mail: paulo.paiva@gmail.com M. Klautau Instituto de Biologia, Departamento de Zoologia, Laboratório de Biologia de Porifera, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil A. M. Solé-Cava Instituto de Biologia, Departamento de Genética, Laboratório de Biodiversidade Molecular, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil