Molecular identification and larval morphology of spionid polychaetes (Annelida, Spionidae) from northeastern Japan Author Abe, Hirokazu https://orcid.org/0000-0002-7753-9368 Department of Biology, Center for Liberal Arts & Sciences, Iwate Medical University, Idaidori 1 - 1 - 1, Yahaba-cho, Shiwa-gun, Iwate 028 - 3694, Japan habe@iwate-med.ac.jp Author Sato-Okoshi, Waka Laboratory of Biological Oceanography, Graduate School of Agricultural Science, Tohoku University, Aramaki-Aza-Aoba 468 - 1, Aoba-ku, Sendai 980 - 8572, Japan text ZooKeys 2021 2021-02-04 1015 1 86 http://dx.doi.org/10.3897/zookeys.1015.54387 journal article http://dx.doi.org/10.3897/zookeys.1015.54387 1313-2970-1015-1 F6BD92139DB74564AA003C61B2F43B2D AF1641758561525C8D40BBF3F895FA8A Scolelepis sp. 2 Fig. 4L Larval morphology. Thick and fusiform in overall shape. Prostomium bluntly pointed anteriorly, terminates in retractile, muscular tip. Lateral parts of peristomium clearly demarcated from prostomium, forming large peristomial umbrella. Peristomial umbrella carrying well-developed prototroch. Short palps developed in late larvae, attached on lateral-most parts of peristomium. Two pairs of red eyes arranged in an approximately straight line. Pharynx widely pigmented orange and the gut pigmented brown. Pygidium broad and spherical shaped. Remarks. No adult individuals of this species were collected in the present study. Even though the 18S and 16S rRNA gene sequences obtained from larvae in the present study did not match any available Scolelepis sequences, this species was referred to Scolelepis sp. 2 as the larvae constitute a monophyletic clade with the other Scolelepis species with robust statistical support (Figs 2 , 3 ). Planktonic larvae of this species were found in Onagawa Bay in September. The larvae of this species are quite similar to those of Scolelepis sp. 1; however, the prostomium is more broadly pointed anteriorly and the gut diverticula are more strongly segmented in the former species.