Morphological and molecular investigation of Scolelepis agilis (Verrill, 1873) (Annelida: Spionidae) from beaches of the Atlantic coast of North America

Polychaete worms of the genus Scolelepis are one of the most abundant members of beach ecosystems worldwide. Along the Atlantic coast of North America, specimens of Scolelepis inhabiting high-energy beaches have long been erroneously identified as the European species Scolelepis squamata (O.F. M & uuml;ller, 1806). In this study, we examined specimens of Scolelepis collected from Massachusetts to Virginia, finding they match Scolelepis agilis (Verrill, 1873), originally described from beaches in New Jersey. Scolelepis agilis can be most easily distinguished from S. squamata based on differences in palp ciliary pattern, morphology of neuropodial lamellae, and the quantity and start of both notopodial and neuropodial hooded hooks. Live specimens of S. agilis collected from New York were also examined to provide data on their reproduction and morphometric analyses. In addition, molecular data (18S, 28S rRNA, cytochrome c oxidase I and 16S rRNA) showed that specimens of S. agilis from the north to mid-Atlantic coast formed a monophyletic group (p-distance <= 0.004 for MA, RI, NY and VA populations) and were distinct from S. squamata (p-distance >= 0.196 (0.03 SE)). The molecular data also suggest the presence of several misidentified or undescribed species of Scolelepis, highlighting the need for additional taxonomic work on the genus from these localities as well as others (e.g. South Africa) where the worms have been incorrectly identified as S. squamata. A key to species of Scolelepis from the east coast of the United States is provided and a lectotype and paralectotypes for S. agilis are herein designated.