Molecular analysis of Spiophanes bombyxcomplex (Annelida: Spionidae) with description of a new species

Abstract

Spiophanes bombyx(Claparede, 1870) from the Gulf of Naples, Tyrrhenian Sea, Italy, was the first describedSpiophaneswith fronto-lateral horns on the prostomium. It was also considered the only horned species occurring in European waters. Our sequence data of five gene fragments suggest the presence of two horned siblingSpiophanesspecies in northern Europe:S. cf.bombyxin the North and the Norwegian seas, andS. cf.convexusin Brittany, northern France, and Bay of Biscay, northern Spain.Spiophanescf.bombyxworms are genetically close to a single examined specimen ofS.bombyxfrom Venice Lagoon, Italy but their conspecificity should be verified by further study. Our sequence data show that hornedSpiophanesfrom the North Pacific are genetically distant from horned European species, and thatS.uschakowiZachs, 1933, originally described from the Sea of Japan (East Sea) is a valid species. The data also suggest the presence of two horned siblingSpiophanesspecies in the North East Pacific:S.hakaiensisRadashevsky & Pankova, n. sp. distributed from Alaska south to about Point Conception, andS.norrisiMeissner & Blank, 2009, distributed from San Francisco Bay south to Baja California Sur, Mexico.Spiophanesfrom South America, morphologically similar toS.norrisi, are suggested to belong to a new species. Molecular data also suggest the presence of two sibling species among the worms from northern Europe identified by morphology asS.kroyeriGrube, 1860. Worms from the Barents Sea and northern part of the North Sea are tentatively referred to asS. cf.kroyeri; worms from the northern and central parts of the North Sea and from the Bay of Biscay, northern Spain, are tentatively referred to asS. cf.cirrataM. Sars in G.O. Sars, 1872. Sequence data also show thatS.duplexfrom California is genetically different from morphologically similar worms from South America. The South American worms are referred to resurrectedS.soederstroemiHartman, 1953 which was originally described from off Rio Grande do Sul, Brazil, and then considered as a junior synonym ofS.duplex. Analysis of divergence times ofSpiophaneslineages suggested that the origin of the most recent common ancestor of hornedSpiophaneswith metameric nuchal organs was around 11.1 mya (95% HPD: 5.1-19.0 mya) and that the divergence of the North Atlantic and North Pacific lineages was around 7.9 mya (95% HPD: 4.1-13.3 mya). The North Atlantic lineage was estimated to have diverged 4.8 mya (95% HPD: 2.2-8.6 mya), resulting in the origin ofS. cf.bombyxandS. cf.convexus. The North Pacific lineage was estimated to have diverged first by the isolation and speciation ofS.norrisi1.7 mya (95% HPD: 2.3-1.0 mya), and then by the isolation and speciation ofS.uschakowiandS.hakaiensisn. sp. 1.3 mya (95% HPD: 2.0-0.7 mya). The estimates place the divergences soon after maximum glacial period in the North Pacific (2.4-3.0 mya).