Newly detected lineage of Branchiomma and the first record of a fan worm Branchiomma sp. B sensu Capa et al. (2013) (Annelida: Sabellidae) from the Japanese Archipelago

Abstract

The fan worm genus Branchiomma (Annelida: Sabellidae) includes 30 valid species. A previous study of the molecular phylogenetic assessment of Branchiomma indicates problems in using traditional morphological diagnostic characters for identification of Branchiomma species. We performed phylogenetic analysis based on the cytb gene sequences of recently collected specimens of Branchiomma from an artificial seawater pond in Iwaki, Fukushima, and from a boat mooring rope at Tanabe Bay, Shirahama, Wakayama, Japan. The Fukushima specimen was identified as a distinct lineage, which was genetically different from the other species of Branchiomma recognized by the previous study. The Shirahama specimens were included in the clade of Branchiomma sp. B sensu Capa et al. (2013) and were identified as this species. The haplotype network illustrated low genetic differences among Branchiomma sp. B specimens collected from Japan, Australia, Hawaii, Saipan, and Florida. More specimens and loci with higher substitution rates would be needed to discuss whether they are spread by unintentional or natural dispersal. The Shirahama specimens of Branchiomma sp. B morphologically differ from Branchiomma cingulatum, the only congener recorded from Japan, in having macrostylodes. However, a substantial revision of the genus and a detailed morphological description of the two species would be necessary to determine whether these two species are indeed distinct. The results of the present study represent the first record of Branchiomma sp. B sensu Capa et al. (2013) from Asia and further extend the known geographic distribution of this wide-ranging species. The 16S rRNA gene sequences were also obtained as reference sequences of DNA barcoding for future studies.