The COI haplotype diversity of the pelagic polychaete Tomopteris (Annelida: Tomopteridae) collected from the Pacific coast off Kii Peninsula, central Japan

Abstract

The polychaete genus Tomopteris is an important component of the zooplankton and is also known for its communication using bioluminescence. However, there have been few studies about the species diversity and ecology of Tomopteris because of taxonomic and handling difficulties resulting from the fragility of their bodies. In this study, we performed DNA barcoding and species delimitation analysis to better understand the species diversity of Tomopteris using 17 specimens collected on a research cruise conducted off the eastern Kii Peninsula, Japan. Due to damage to the detailed morphological characteristics necessary for identifications based on the current taxonomy, none of the specimens was morphologically identifiable at the species level. The analyses of the mitochondrial cytochrome c oxidase subunit I (COI) and nuclear large ribosomal subunit (28S) RNA gene sequences revealed 7–8 molecularly delimited species among them, which was greater than the number of species currently recognized in Japan. These results suggest that the traditional morphology-based taxonomy overlooks the taxonomic complexity of Tomopteris, thus a combinatory analysis of both morphology and DNA barcoding will be desirable for assessing the true species biodiversity of Tomopteris.