Daylithos sugashimaensis, Jimi & Fujita & Woo, 2023

Jimi, Naoto, Fujita, Toshihiko & Woo, Sau Pinn, 2023, Four new species of coral- and rock-boring polychaetes Daylithos (Annelida, Flabelligeridae) from the Pacific Ocean, Zoosystematics and Evolution 99 (1), pp. 149-159 : 149

Daylithos sugashimaensis sp. nov.

Fig. 4

Type material.

Holotype (NSMT-Pol H-909): complete, off Sugashima Island (34.4951°N, 136.9112°E), 20 m depth, collected by gillnet, Naoto Jimi, 21 Apr 2022. Paratypes (NSMT-Pol P-910): two specimens, complete, collected with holotype, 21 Apr 2022. Paratypes (NSMT-Pol P-911): three specimens, complete, off Sugashima Island (34.4946°N, 136.9161°E), 75 m depth, collected by gillnet, Naoto Jimi, 27 Apr 2022. Paratypes (NSMT-Pol P-912): one broken specimen (identified with DNA sequence), Hikottoland Marine Beach, Yamaguchi (33.9451°N, 130.8974°E), intertidal, collected by hand, Teppei Kushimoto, 27 Apr 2022.

Description

(based on holotype). Body 30 mm in total length (14-60 mm in paratypes), 3 mm in width (1-4 mm in paratypes), 84 chaetigers (70-106 chaetigers in paratypes), greyish, cylindrical, tapering posteriorly into flat cauda (Fig. 4A ). Tunic thin, without sediment particles, pale. Dorsal shield flat, without depression or projection (Fig. 4B ). Body papillae minute, distally rounded, arranged in two rows per segment, papillae of anterior row similar size to posterior row. Gonopodial lobes not seen. Neuropodial base of chaetiger 5 slightly swollen.

Prostomium oval. Eyes present, blackish. Caruncle slightly exceeding the branchial plate margin. Dorsal and lateral lips present (Fig. 4C, D ); ventral lip smaller than dorsal and lateral lips. Palps thicker than branchiae. Branchiae in two lateral groups, each with 25 filaments. Longest branchiae in inner rows, about 2/3 as long as palps, decreasing in length towards lateral margins. Nephridial lobes not seen. Large branchiae two times wider than smaller branchiae.

Cephalic cage chaetae about 1/3 body length, four times as long as body width (Fig. 4A, B ). Chaetiger 1-2 comprising cephalic cage; chaetiger 1 with 10 notochaetae and 10 neurochaetae per side; chaetiger 2 with 8 notochaetae and 8 neurochaetae per side. Chaetiger 1 1.5 times longer than chaetiger 2. Chaetae of chaetiger 3 four times longer than the following ones, not contributing to the cephalic cage. Chaetal transition from cephalic cage to body chaetae abrupt.

Notopodia poorly developed, lateral; neuropodia ventrolateral in median body. Notopodia and neuropodia widely separated. Parapodial lobes absent. Notochaetae multi-articulated capillaries, transparent, 1/4 maximum body width, 2-4 per bundle, with about 90 articles (Fig. 4E ); articles medium-sized distally (30 times as long as wide), short medially and basally (1/2 times as long as wide) (Fig. 4F ). Neurochaetae multi-articulated aristate capillaries in chaetigers 1 to 8, 2-5 per bundle. Neurohooks present in chaetiger 9, arranged in short transverse rows, golden (Fig. 4G, H ), 1-2 large barely falcate anchylosed hooks with very small anchylosed 2-3 hooks per ramus in anterior chaetigers, 2-4 in posterior chaetigers, curved. 30-40 anchylosed articles in larger hooks, 40-50 anchylosed articles in smaller hooks.

Posterior end depressed; pygidium with anus terminal, anal cirri absent.

Oocytes inside middle part of body, blackish in ethanol.

Etymology.

this species is named after the type locality (Sugashima Island).

Distribution.

intertidal to subtidal area of South Japan; 0-75 m depth; inside of rocks (mudstone).

Remarks.

Daylithos sugashimaensis sp. nov. resembles D. amorae Salazar-Vallejo, 2012 and D. nudas (Caullery, 1944) in having the greyish body in fixed material and 2-4 neurohooks in posterior chaetigers. However, D. sugashimaensis can be discriminated from the two other species by having two rows of body papillae as opposed to one row, neurohooks present from chaetiger 9 and dorsal shield without posterior projection. While neurohooks of D. sugashimaensis are present from chaetiger 9, those of D. amorae are from chaetiger 7; and in D. nudus , are from chaetiger 6. Body papillae of D. sugashimaensis and D. nudus are two rows, but of D. amorae are one row. While the dorsal shields of D. nudus and D. amorae are with posterior projections, D. sugashimaensis is without posterior projection.

Figures

Figure 4. Daylithos sugashimaensis sp. nov. Holotype (NSMT-Pol H- 909). A. Whole body, lateral view; B. Anterior end, lateral view; C. Prostomium, frontal view; D. Prostomium, lateral view; E. Notochaetae, chaetiger 12; F. Basal part of notochaetae; G. Neurohook, chaetiger 12; H. Middle part of neurohook. Scale bars: 5 mm (A, B); 2 mm (C); 1 mm (D); 200 μm (D); 100 μm (E); 200 μm (F); 100 μm (G). Abbreviations: cc, cephalic cage; ca, caruncle; p, palp; dl, dorsal lip; ll, lateral lip; vl, ventral lip.