Prionospio krusadensis Fauvel, 1929

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 krusadensis Fauvel, 1929 Fig. 5C, D

Larval morphology.

Long and thin in shape. Prostomium rounded anteriorly, lateral parts of the peristomium not especially well demarcated. Two pairs of red eyes arranged somewhat in trapezoidal shape, lateral pair kidney-shaped and situated anteriorly. Body extremely transparent (Fig. 5D ). Green pigmentation on pharynx and pygidium (Fig. 5C, D ). Caruncle develop in late larvae, extends posteriorly from posterior part of prostomium (Fig. 5C ). In late larvae, branchial anlages occur from chaetiger II, pygidium acquires anal cirri.

Remarks.

Adult individuals of this species were collected from shallow subtidal muddy bottom sediments in Sasuhama in August 2011 by using a hand-scoop. The species was referred to P. krusadensis as the adult morphology agrees with the descriptions of this species by Imajima (1990a). The larvae and adults were confirmed to match (18S: 1749/1749, 16S: 506/507 bp) using molecular data (Fig. 2 ).

Planktonic larvae of this species were found in Sasuhama and Onagawa Bay in July and August, but they were rare in the plankton samples. Green pigmentation on the pharynx and pygidium is characteristic of the larvae of this species.

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 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.