Prionospio spp. 1 and 2

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

Prionospio spp. 1 and 2 Fig. 5H, I

Larval morphology.

Long and thin in shape. Prostomium rounded anteriorly, lateral parts of the 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 the prostomium. In Prionospio sp. 2, branchial anlages occur from chaetiger II, pygidium acquires anal cirri (Fig. 5I ). Pigmentation absent except eyes in Prionospio sp. 1. Gut pigmented in orange in Prionospio sp. 2. Palps developed in 19-chaetiger larva of Prionospio sp. 2.

Remarks.

Two unidentified species of planktonic larvae of the genus Prionospio other than P. krusadensis and P. membranacea were collected from Onagawa Bay. The adult individuals of these species were not collected in the present study. Even though the 18S and 16S rRNA gene sequences obtained from these larvae in the present study did not match any Prionospio sequences obtained in the present study nor with those registered in DDBJ/EMBL/GenBank, these species were referred to Prionospio sp. 1 and 2 as the larvae were similar to the other Prionospio species in their morphology and gene sequences (Figs 2 , 3 ). The larvae of Prionospio sp. 1 and 2 are similar to each other and to that of P. membranacea , and it is difficult to distinguish among them based only on their morphology.

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 5. Light micrographs showing the morphologies of living spionid larvae of genera Paraprionospio and Prionospio A, B Paraprionospio coora, lateral view of 25 - chaetiger (A) and 33 - chaetiger larvae (B) C, D Prionospio krusadensis, lateral view of 17 - chaetiger larvae E-G Prionospio membranacea, lateral view of 15 - chaetiger (E), 20 - chaetiger (F), and 24 - chaetiger larvae (G) H, Prionospio sp. 1, lateral view of 11 - chaetiger larva I Prionospio sp. 2, lateral view of 19 - chaetiger larva. Scale bars: 300 μm.