A morphometric analysis of Eunice Cuvier (Annelida, Polychaeta) species

Morphology has been the subject of several studies in Eunice specially in the context of the taxonomy and evolutionary relationships of taxa within this genus. In this study we opt for a morphometric approach comparing five species of Eunice to assess if it was possible to delimitate them by shape variables. The morphology of E. fucata, E. insularis, E. cf. ornata, E. rubra, and Eunice sp. was compared using traditional morphometric analysis of 16 measured variables. After removing the size-effect, a Canonical Variates Analysis applied to morphometric variables was able to discriminate all species. In CV1 two major groups of species were discriminated: E.fucata/E. insularis and E. cf. ornata/E. rubra/Eunice sp. CV2 strongly discriminated all species, with E. cf. ornata with higher scores and E. rubra with lower ones. The characters that differentiate the species were the relative size of antennae, peristomium and anteriormost setigers. This study also demonstrated that peristomium width and palps length were the best variables for body size estimation in Eunice, since they were highly correlated to the size-estimator. Through morphometric analysis it was possible to delimitate species and choose diagnostic characters for the genus Eunice, a result likely to be valid for other polychaete species.