Polydora sp. 1

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

Polydora sp. 1 Fig. 8K, L

Larval morphology.

Overall body shape slender. Prostomium broad and rounded anteriorly. Three pairs of black eyes present; median eyes rounded and lateral pairs double-eyes. Ramified melanophore between innermost and next to innermost pairs of eyes absent. Weak brown pigmentation on lateral parts of peristomium present or absent. Dorsal pigmentation consists of two rows of melanophores from chaetiger III, those of first five pairs band-shaped and remaining pairs dot-like in late larvae (Fig. 8L ). These melanophores all dot-like in early larvae (Fig. 8K ). Lateral pigment found on chaetigers II, IX, X, and XI in late larvae. Dorsolateral pigment at base of parapodia on posterior chaetigers. A pair of black and brown pigment patches occur on pygidium. Ventral brown pigment present on posterior part of late larvae. Pygidium has a dorsal notch and lacks appendages. Telotroch well developed. In late larvae, modified chaetae develop in 5th chaetiger.

Remarks.

Adults of this species are shell-borer and were collected from the shell of the turban snail O. rusticus in Sasuhama. The adults of this species have characteristic conspicuous black bars in their palps and are morphologically similar to Polydora neocaeca Williams & Radashevsky, 1999. Polydora haswelli previously recorded in Japan ( Sato-Okoshi and Abe 2013) was reexamined as P. neocaeca by comparing morphology and molecular sequences with the specimens from near the type locality ( Malan et al. 2020). As the 18S and 16S rRNA gene sequences of Polydora sp. 1 and P. neocaeca showed differences (18S: 8/1771, 16S: 40/476 bp), the specimens collected in the present study were referred to a different species. Only two individuals of planktonic larvae of this species were collected in Onagawa Bay in April and July 2011. The larvae and adults were confirmed to 100% match using molecular data (Fig. 2 ).

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 8. Light micrographs showing the morphologies of living spionid larvae of the genus Polydora A, B Polydora brevipalpa, dorsal view of 15 - chaetiger (A) and 17 - chaetiger larvae (B) C, D Polydora cornuta, dorsolateral view of 11 - chaetiger larva (C) and ventral view of 17 - chaetiger larva (D) E Polydora cf. glycymerica, dorsal view of 25 - chaetiger larva F Polydora hoplura, dorsal view of 15 - chaetiger larva G-I Polydora onagawaensis, dorsal view of 10 - chaetiger (G) and 18 - chaetiger larvae (H), and lateral view of 16 - chaetiger larva (I) J Polydora cf. spongicola, dorsal view of 17 - chaetiger larva K, L Polydora sp. 1, dorsal view of 7 - chaetiger (K) and 16 - chaetiger larvae (L) M Polydora sp. 2, dorsal view of 23 - chaetiger larva N-P Polydora sp. 3, dorsal view of 13 - chaetiger (N) and dorsal (O) and lateral view (P) of 18 - chaetiger larvae. Scale bars: 300 μm.