Prionospio membranacea Imajima, 1990 Fig. 5E-G

Larval morphology.

Long and thin in shape. Prostomium rounded anteriorly, lateral parts of peristomium not especially well demarcated. Two pairs of red or dark red eyes arranged somewhat in trapezoidal shape, lateral pair kidney-shaped and situated anteriorly. Small caruncle develop in late larvae, extends posteriorly from posterior part of prostomium (Fig. 5G). In late larvae branchial anlages occur from chaetiger II, pygidium acquires anal cirri (Fig. 5G). Palps not yet developed in 15- and 20-chaetiger larva (Fig. 5E, F) but developed in 24-chaetiger larva (Fig. 5G). Pigmentation absent except eyes.

Remarks.

Adult individuals of this species were collected from muddy bottom sediments at 22 m depth in Onagawa Bay in December 2011 by using a Smith-McIntyre grab sampler. The species was referred to P. membranacea as the adult morphology agrees with the descriptions of this species by Imajima (1990b). The larvae and adults were confirmed to match (18S: 1752/1752 and 1747/1750 except for gaps, 16S: 502/505 bp) using molecular data (Fig. 2). Planktonic larvae of this species were found in Onagawa Bay during August to October.