Scolelepis cf. kudenovi Hartmann-Schroeder , 1981

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

Scolelepis cf. kudenovi Hartmann-Schroeder, 1981 Fig. 4I

Larval morphology.

Thick and fusiform in shape. Prostomium pointed anteriorly, terminates in retractile, muscular tip. Lateral parts of peristomium clearly demarcated from prostomium, forming peristomial umbrella. Peristomial umbrella carrying well-developed prototroch. Two pairs of red eyes arranged in somewhat trapezoidal shape, medial pair situated anteriorly. Greenish pigment in pharynx and proctodaeum. Pygidium very broad and horseshoe-shaped.

Remarks.

Only three individuals of early larvae of this species were collected from Sasuhama in January 2012. The 18S rRNA gene sequences obtained in the present study for these specimens match (464/464 bp) that of S. kudenovi from Lizard Island, Australia (KP636517: Meißner and Götting 2015). Since the species identification is unreliable because of the short reference sequence, this species was referred to S. cf. kudenovi .

The sequence of an adult individual, which collected from the surf zone of the sandy beach in Rishiri Island and previously identifies as Scolelepis kudenovi ( Abe et al. 2019c) as the morphology agrees with the descriptions of S. kudenovi by Imajima (1992) and Meißner and Götting (2015), 100% matched with that of the larvae of Scolelepis cf. kudenovi in 18S rRNA gene (1819/1819 bp) but largely differed in 16S rRNA gene (462/505 bp). Because the 16S rRNA gene of the adult individual was rather closer to S. daphoinos (430/455 bp) from China (GU362676, Zhou et al. 2010), it is referred to S. aff. daphoinos in the present study (Table 1 , Figs 2 , 3 ).

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 4. Light micrographs showing morphologies of living spionid larvae of Aonides, Laonice, Rhynchospio, Scolelepis, and Spiophanes A-C Aonides cf. oxycephala, dorsal view of early planktonic (A), 8 - chaetiger (B), and 18 - chaetiger larvae (C) D Laonice sp. 1, dorsal view of early planktonic larva E Laonice sp. 2, dorsal view of 12 - chaetiger larva F Poecilochaetus sp., dorsal view of 17 - chaetiger larva G, H Rhynchospio aff. asiatica, dorsal view of 6 - chaetiger (G) and 12 - chaetiger larvae (H) I Scolelepis cf. kudenovi, dorsal view of 7 - chaetiger larva J, K Scolelepis sp. 1, dorsal view of 17 - chaetiger (J) and 19 - chaetiger larvae (K) L Scolelepis sp. 2, dorsal view of 20 - chaetiger larva M, N Spiophanes uschakowi, dorsal (M) and lateral view (N) of 18 - chaetiger larvae O, P Spiophanes aff. uschakowi, dorsal view of 16 - chaetiger larva (O) and 27 - chaetiger juvenile (P). Scale bars: 300 μm.