Pseudopolydora sp.

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

Pseudopolydora sp. Fig. 9I

Larval morphology.

Overall larval shape slightly fusiform, head region enlarged due to broad prostomium and expanded lateral lips of vestibule. Prostomium rounded anteriorly. Three pairs of black eyes present, comprising one pair of rounded median eyes, one pair of large lateral eyes, and one pair of large anterior eyes. Lateral and anterior pairs of eyes link with each other and form a dumbbell-shape almost divided into two equal parts by a deep constriction. Small mid-dorsal melanophore present on chaetiger I. A distinct paired melanophore occurs dorso-laterally from chaetiger II onwards, ramified in anterior chaetigers. Black pigment spots on sides of peristomium absent. Dot-like black pigmentation on pygidium.

Remarks.

No benthic adult stages were collected in the present study. The larvae formed a monophyletic clade with the other Pseudopolydora species with> 50% bootstrap support (Figs 2 , 3 ). Therefore, this species was identified as a member of Pseudopolydora . As the 18S rRNA gene sequences obtained from the larvae did not match any of the available Pseudopolydora sequences, this species is referred to Pseudopolydora sp.

Only one larva individual was collected from Sasuhama in August 2011. The dorsal pigment pattern of this larva somewhat resembles that of P. paucibranchiata ; however, the mid-dorsal pigment of this species is weaker and its dorsolateral melanophores are more ramified than those of P. paucibranchiata . The eye arrangement of this larva resembles that of late P. tsubaki larvae: three pairs of black eyes are present, but not in a straight line.

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 3. Maximum Likelihood tree inferred from nuclear 18 S and mitochondrial 16 S rRNA gene sequences of spionid polychaetes obtained from Japan in the present and previous studies (shown in Table 1) and from DDBJ / EMBL / GenBank (shown in Table 2). The tree is divided into two parts A, B. The gene sequences obtained in the present study are highlighted by bold and red color and the adult and larval sequences 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 GenBank were used for outgroup rooting.

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.