Escarpia southwardae sp nov., a new species of vestimentiferan tubeworm (Annelida, Siboglinidae) from West African cold seeps

A new species of vestimentiferan tubeworm belonging to the genus Escarpia is described from cold seeps off the western coast of Africa. The description is based on two collections (one of 180 animals, the other of 30 animals) using both morphological and molecular techniques. Morphologically, the African tubeworms are very similar to Escarpia laminata Jones, 1985 but differ from all other escarpids by the lack of branchial pinnules, a unique feature among vestimentiferans. Molecular evidence from sequences of the cytochrome-c oxidase subunit I gene places the species in the escarpid clade, closely related to E. laminata and Escarpia spicata Jones, 1985, but fails to discriminate among the three species. Four morphotypes are identified in the African species, corresponding to the four permutations of the following characters: presence or absence of an axial rod on the obturaculum and presence or absence of a split on the posterior ventral margin of the vestimentum. However, molecular data could not distinguish them as separate species. We suggest that the lack of an axial rod reflects predation. Biometrical data indicate a discontinuous recruitment period, as is known for other vestimentiferan species. Sex ratios are balanced, but females tend to be larger than males. We hypothesize that the males grow more slowly or die younger than the females.