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 Polydora onagawaensis Teramoto, Sato-Okoshi, Abe, Nishitani & Endo, 2013 Fig. 8G-I Larval morphology. Overall body shape slender. Prostomium slightly broad and rounded anteriorly. Three pairs of black eyes present; median pair of eyes rounded, most lateral pairs double-eyes. Ramified melanophore between middle and lateral pair of eyes usually present (Fig. 8G, H ). Weak brown pigmentation located on lateral parts of peristomium, behind prototroch, occasionally much paler or absent. Dorsal pigmentation consists of two rows of melanophores from chaetiger III with those of first IV-VI band-shaped and subsequently replaced by ramified melanophores. These melanophores undergo expansion and contraction. Lateral pigment found on chaetigers II and III in late larvae (Fig. 3G ). Dorsolateral pigment at base of most parapodia, often appears to coalesce with dorsal pigment bands on anterior part of body (Fig. 8H ). Pygidium has a dorsal notch and lacks appendages; a pair of black pigment patches occur on pygidium. Ventral brown pigment may be present on posterior part of late larvae (Fig. 8I ). Telotroch well developed. Gastrotrochs on chaetigers III, V, VII, X, XIII, and XV; those of chaetigers III and V lost in late larvae (Fig. 8I ). In late larvae, modified chaetae develop in chaetiger V. Remarks. This species is a shell-borer, and adult individuals were collected from shells of the wild turban snail O. rusticus , cultured scallop M. yessoensis , and wild and cultured C. gigas oysters in Onagawa Bay and Sasuhama, northeastern Japan. This species was identified as P. onagawaensis as adult morphology agrees with the description by Teramoto et al. (2013) . The larvae and adults were confirmed to match (18S: 1771/1771, 16S: 472/473 bp) using molecular data (Fig. 2 ). Planktonic larvae of this species were abundant from November to June in Onagawa Bay during the study period. The larval morphology of this species is similar to that of Polydora sp. 3 (see below). However, the former species has weak brown pigmentation on the lateral parts of the peristomium, whereas the latter species has large patches of black pigment on this region.