Lumbrinerides yoshioi Miura 2017, sp. nov.

Lumbrinerides yoshioi sp. nov. (Figs 18, 19)

Material examined. Holotype: NSMT-Pol H-618, off Tomakomai, Hokkaido, 42°36.7′N 141°37.6′E, 10–20 m, fine muddy sand, June 1986; 10 paratypes: NSMT-Pol P-619, 10 immature, same site and date as holotype.

Non-type material. (TOMA) 19 juveniles, same site and date as holotype.

Description. The holotype (29.3 mm long by 0.86 mm wide) has 54 chaetigers (many posterior chaetigers lost).

Prostomium length 3.13 times width in holotype, greater than twice width in most adults (Fig. 18A). Peristomium comprising two apodous rings. Nine anterior parapodia reduced, subsequent postchaetal lobes becoming larger, fully developed parapodia on chaetiger 12 or more posteriorly (Fig. 18D). First nine or ten parapodia with two broadly limbate chaetae when intact (Fig. 19). Three limbate chaetae per parapodium on chaetigers 11–30 or somewhat posteriorly, sometimes four or five limbate chaetae on a single parapodium. One or two limbate chaetae on chaetiger 40 or more posteriorly. Simple bidentate hooded hooks begin on first parapodium, two per parapodium on the first nine to eleven parapodia, one on chaetigers 12–32, two or three on chaetigers 32 and posteriorly in holotype (Fig. 19). Mandibles with six concentric lines in holotype, four to nine in large paratypes (Fig. 18C). Maxillae I with two weakly projected accessory teeth with internal cavities on both forceps in all type specimens (Fig. 18B). Maxillae II with three blunt intermeshing teeth on both plates.

Biological notes. All of the specimens from Tomakomai lacked a considerable number of posterior chaetigers. Although maturation details are unknown, the presence of some posterior fragments with oocytes in the collection indicated a spawning season near early summer. The collection comprised two clearly defined size classes of specimens (Fig. 2). Eleven larger specimens (0.83–0.99 mm in body width) were thought to be adults, their mandibles having four to nine concentric lines on the cutting edges. The remaining 19 juvenile specimens (0.36–0.66 mm in body width) had two to four such concentric lines.

Variations. The number of anterior reduced parapodia varied from eight to ten in adult specimens and seven to nine in juveniles. The prostomial length to width proportion was slightly higher in larger specimens (1.99–3.42, average 2.39) compared 1.90–3.55 (average 2.34) in juveniles. The first hooded hooks always began on chaetiger 1. The number of accessory teeth on Maxillae I was two in most specimens except for one with three teeth on both forceps. Maxillae II always had three intermeshing teeth in each plate.

Remarks. This new species has a uniquely long prostomium among Japanese species. Although Lumbrinerides acutiformis from Nha Trang also has a very long prostomium, the proportion of length to width is 3.5–4.0, greater than that of adults of the new species (1.99–3.42).

Etymology. The new species epithet is named for Yoshio Miura, my late father, who had been in Tomakomai city and supported in part my stay in France for the lumbrinerid study.

Distribution. Off Tomakomai, Hokkaido (10–20 m), Pacific coast of Japan, known only from the type locality.