Morphological investigation and analysis of ribosomal DNA phylogeny of two scale-worms (Polychaeta, Polynoidae) from the Gulf of Thailand

Scale-worms are polychaetes of the family Polynoidae that are commonly distribute in marine environments. This study aims identify and introduce two scale-worms as Capitulatinoe cf. cupisetis and Eunoe cf. oerstedi from the western coast of the Gulf of Thailand. Using scanning electron microscopy of adult worms, the antennae, palps, prostomium, cirri, setigers, parapodia, saetae and elytra are described. In addition, the phylogenetic relationships of our specimens with other polychaete species were analyzed based on partial sequences of 28S, 18S and 16S ribosomal DNA (rDNA) genes. The rDNA sequences identified C. cf. cupisetis and E. cf. oerstedi were respectively recovered within Arctonoinae and Polynoinae in a monophyletic Polynoidae. The congruence or incongruence of the morphological and molecular data is discussed in the text. These findings increase the knowledge of polynoid polychaete worms in Thailand, although two scale-worms remain to be identified of the precise species