Diplocirrus ohtsukai, Jimi & Fujiwara & Kajihara, 2017

Jimi, Naoto, Fujiwara, Yoshihiro & Kajihara, Hiroshi, 2017, Remarkable biodiversity of flabelligerids in Japan: seven new species of Diplocirrus (Annelida: Flabelligeridae) from Japanese waters, Zootaxa 4337 (3) : -

Diplocirrus ohtsukai sp. nov.

(New Japanese name: Ohtsuka-konbou-habouki) ( Figure 4 )

Type materials. Holotype: NSMT-Pol H-638, Hibiki-nada, 62 m depth, collected by NJ, COI sequence DDBJ accession no. LC314565 . Paratypes: NSMT-Pol P-639, Hibiki-nada, 62 m depth, six incomplete specimens (5–24 mm long, 1.5–2.0 mm wide, 10–21 chaetigers).

Description. Holotype incomplete, 16 mm long, 3 mm wide (in chaetiger 10), 19 chaetigers. Body with first 13 chaetigers swollen, cylindrical ( Fig. 4A ). Tunic whitish in ethanol with fine sediment particles on body wall and papillae ( Fig. 4B ); particles present on whole body wall except cephalic hood. Digitate papillae in whole body abundant, longer than wide, short, in median chaetigers about 1/25 as long as notochaetae and half as long as lateral papillae in chaetal lobe, arranged in 14–15 transverse rows per segment. Cephalic hood transparent, with papillae near 1 st chaetiger . Gonopodial lobes not seen. Gonopores present in chaetigers 3–12, white ( Fig. 4B ). Posterior region tapered; anal part lost in holotype.

Two types of branchiae present: dorsal branchiae 3 mm long, thick, with single lobe in internal side, not lamellate ( Fig. 4C ); ventral branchiae 7 mm long, thin, smooth, not lamellate ( Fig. 4D ). Palps 8 mm long, grooved. Upper and lateral lips well developed. Caruncle projected, not separating dorsal branchiae ( Fig. 4E ). Eyes absent. Nephridial lobes present.

Parapodia poorly developed, chaetae emerging from body wall; notopodia with 3–5 lateral papillae on anterior side and no lateral papillae on posterior side; neuropodia with 5–7 lateral papillae on anterior side and 2 lateral papillae on posterior side. Cephalic cage developed (1 st notochaeta 2.0 mm in length). Notochaetae 7–9 per bundle, multiarticulate ( Fig. 4F ) with 51–59 articles in chaetiger 20; tip tapered. Neurochaetae 4–5 per bundle, multiarticulate ( Fig. 4G ) with 8–13 articles in chaetiger 20, rounded projection poorly developed; subdistal article 3–4 times longer than wide; tip slightly falcate.

Distribution. Only known from type locality (Hibiki-nada, 62 m depth).

Etymology. This species is named after Prof. Susumu Ohtsuka who organized the research cruise of the R/V Toyoshio -maru at the type locality, Hibiki-nada. The specific name is a noun in the genitive case.

Remarks. Diplocirrus ohtsukai sp. nov. resembles D. salazarvallejoi Teixeira, Rizzo & Santos, 2015 (originally described from Brazil) in the following features: i) body papillae are short and abundant, ii) body is covered with sand particles, iii) lateral papillae are short, iv) anterior chaetigers are swollen, and v) gonopores are present. The two species can be discriminated by i) size of the cephalic cage and ii) position of the swollen area in the body. The cephalic cage of D. ohtsukai sp. nov. is well developed (2/3 of body width), whereas that of D. salazarvallejoi is not (1/4 of body width). The swollen area in D. ohtsukai sp. nov. is along first 12–13 chaetigers, whereas it is along 8 chaetigers in D. salazarvallejoi .

Figures

FIGURE 4. Diplocirrus ohtsukai sp. nov., Holotype (NSMT-Pol H- 638). A, whole body, ventrolateral view. B, body wall, ventral view; arrow indicates gonopore. C, dorsal branchia. D, ventral branchia. E, prostomium. F, notochaetae, chaetiger 20. G, neurochaetae, chaetiger 20 (insert: chaetal tip). Abbreviations: BS, branchial scar; Ca, caruncle; LL, lateral lip; NL, nephridial lobe; PS, palp scar. Scale bars: A, 5 mm; B – E, 500 µm; F – G, 100 µm.