Dipolydora cf. socialis (Schmarda, 1861)

Abe, Hirokazu & Sato-Okoshi, Waka, 2021, Molecular identification and larval morphology of spionid polychaetes (Annelida, Spionidae) from northeastern Japan, ZooKeys 1015, pp. 1-86 : 1

Dipolydora cf. socialis (Schmarda, 1861) Fig. 7O

Larval morphology.

Late larvae usually thick and slightly fusiform in shape, although not as much as the larvae of Boccardia sp. 2 (Fig. 7G ), Boccardiella hamata (Fig. 7H, I ), and Pseudopolydora species (Fig. 9A-I ). Anterior margin of prostomium has yellow-brown pigment. Three pairs of black eyes arranged in transverse row, most lateral pairs double-eyes. Band of black pigment on each lateral part of the peristomium. First dorsal black melanophores occur as paired bands on chaetiger III and continue through to chaetiger V. From chaetiger VI, two pairs of dorsal black spots or bands occur and continue to posterior end of body. From chaetiger IV or V and continuing posteriorly, clusters of small black pigmented cells present in transverse row on dorsal posterior half of chaetigers. Lateral pigment found on late larvae on chaetiger II. Each notopodial lobe tipped with orange pigment, small patch of black pigment at the base of notopodial lobes. Ventral pigment consists of paired bars on posterior border of chaetigers, commencing with chaetiger II. Some black or brown pigment may occur on pygidium. Gastrotrochs occur on chaetigers III, V, VII, X, XIII, XV and XVII.

Remarks.

Adults of this species were non-boring and collected from muddy bottom sediment at 22 m depth in Onagawa Bay in December 2010 by using a Smith-McIntyre grab sampler and from bottom sediments of shallow subtidal zone in Sasuhama in April 2013. Adult morphology agrees with the description of D. socialis by Sato-Okoshi (2000). The 18S rRNA gene sequence obtained in the present study showed a 0.35% (6/1715 bp) difference with that of D. cf. socialis from South Africa (KY677899) reported by Williams et al. (2017), which may indicate that these two are different species. The 18S rRNA gene sequence obtained in the present study rather closer to that of D. carunculata (940/942 bp match) reported by Radashevsky and Pankova (2013), but the 16S gene sequence showed a 2.3% (11/475 bp) difference with that of D. carunculata . As described above, since the taxonomic status of the species reported here is uncertain, we tentatively referred to it as D. cf. socialis .

Planktonic larvae of this species were collected from Onagawa Bay in November 2010 and 2011, and in October 2012. The larvae and adults were confirmed to match (18S: 1770/1770, 16S: 473/475 bp) using molecular data (Fig. 2 ). The larval morphology of this species agrees with that of D. socialis described as Polydora socialis by Blake (1969) and Carrasco (1976).

Figures

Figure 2. Maximum Likelihood tree inferred from nuclear 18 S and mitochondrial 16 S rRNA gene sequences of spionids obtained from Japan in the present and previous studies (provided in Table 1). The gene sequences of adult and larval spionid polychaetes are indicated by solid squares and circles in front of each species name, respectively. SH-aLRT / approximate Bayes support / ultrafast bootstrap support values of ≥ 80 %, ≥ 0.95, ≥ 95 %, respectively are given beside the respective nodes. Nodes with red circles indicate triple high support values of SH-aLRT ≥ 80, approximate Bayes support ≥ 0.95, and ultrafast bootstrap support ≥ 95. The scale bar represents the number of substitutions per site. Sequences of Laonome sp. and Sabella pavonina Savigny, 1822 obtained from DDBJ / EMBL / GenBank were used for outgroup rooting.

Figure 7. Light micrographs showing the morphologies of living spionid larvae of genera Boccardia, Boccardiella, and Dipolydora A, B Boccardia proboscidea, dorsal view of accidentally hatched 9 - chaetiger (A) and 15 - chaetiger larvae (B) C Boccardia pseudonatrix, dorsal (left) and ventral (right) view of accidentally hatched 10 - chaetiger larvae D-F Boccardia sp. 1, dorsal view of 9 - chaetiger (D) and dorsal (E) and ventral view (F) of 17 - chaetiger larvae G Boccardia sp. 2, dorsal view of 15 - chaetiger larva H, I Boccardiella hamata, dorsal view of 16 - chaetiger (H) and 18 - chaetiger larvae (I) J, K Dipolydora bidentata, dorsal view of 13 - chaetiger (J) and 18 - chaetiger larvae (K) L Dipolydora cf. commensalis, dorsal view of 21 - chaetiger larva M, N Dipolydora giardi, dorsal view of 19 - chaetiger (M) and lateral view of 21 - chaetiger larvae (N) O Dipolydora cf. socialis, dorsal view of 18 - chaetiger larva P Dipolydora sp., dorsal view of 7 - chaetiger larva. Scale bars: 300 μm.

Figure 9. Light micrographs showing the morphologies of living spionid larvae of genera Pseudopolydora and Spio A, B Pseudopolydora aff. achaeta, dorsal view of 12 - chaetiger (A) and 25 - chetiger larvae (B) C Pseudopolydora cf. kempi, dorsolateral view of 12 - chetiger larva D Pseudopolydora paucibranchiata, dorsal view of 13 - chaetiger larva E, F Pseudopolydora cf. reticulata, dorsal view of 17 - chaetiger (E) and 16 - chaetiger larvae (F) G, H Pseudopolydora tsubaki, dorsal view of 5 - chaetiger (G) and 11 - chaetiger larvae (H) I Pseudopolydora sp., dorsal view of 7 - chaetiger larva J, K Spio sp. 1, dorsal view of 8 - chaetiger (J) and lateral view of 12 - chaetiger larvae (K) L-N Spio sp. 2, dorsal view of 10 - chaetiger (L) and 17 - chaetiger larvae (M), and 17 - chaetiger metamorphosing larvae (N). Scale bars: 300 μm.