Diplocirrus seisuiae, 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 seisuiae sp. nov.

(New Japanese name: Seisui-konbou-habouki) ( Figure 5 )

Type materials. Holotype: NSMT-Pol H-640, Kumano-nada, 339–362 m depth, collected by NJ, COI sequence DDBJ accession no. LC314566 . Paratypes: NSMT-Pol P-641, Kumano-nada, 339–362 m depth, collected by NJ, four specimens are incomplete (6–15 mm long, 0.8–1 mm wide, 14–25chaetigers); NSMT-Pol P-642, off Jyogashima, 230–398 m depth, collected by Dr. Masaatsu Tanaka, three incomplete specimens (6–10 mm long, 1– 2 mm wide, 12–23 chaetigers).

Description. Holotype incomplete, 23 mm long, 2 mm wide (in chaetiger 10), 20 chaetigers. Body with first 15 chaetigers swollen, thereafter cylindrical ( Fig. 5A ). Tunic whitish in ethanol with sediment particles on whole body wall (except cephalic hood) and papillae ( Fig. 5B ). Anterior part of body (chaetigers 1–3) with a rusty color. Digitate papillae abundant, longer than wide, short, in median chaetigers about 1/6 as long as notochaetae and 1/5 as long as lateral papillae in chaetal lobe, arranged in 7–8 transverse rows per segment. Cephalic hood transparent, without papillae. Gonopodial lobe and gonopores absent. Posterior region tapered; anal part lost in holotype.

Two types of branchiae present: dorsal branchiae, 1.0 mm long, thick, with one lobe in internal side, not lamellate ( Fig. 5C ); ventral branchiae, 1.6 mm long, thin, smooth, small lamellae on dorsal side of base ( Fig. 5D ). Palps 2.0 mm long, grooved. Upper and lateral lips well developed. Caruncle poorly projected, not separating dorsal branchiae ( Fig. 5E ). Eyes absent. Nephridial lobes present.

Parapodia poorly developed, chaetae emerging from body wall; notopodia with no lateral papillae on anterior side and 3–5 lateral papillae on posterior side; neuropodia with 1 lateral papilla on anterior side and 1 lateral papilla on posterior side. Cephalic cage developed (1 st notochaeta 2.0 mm long). Notochaetae 2–7 per bundle, multiarticulate ( Fig. 5F, G ) with 41–45 articles in chaetiger 20; tip tapered. Neurochaetae 5–6 per bundle, multiarticulate ( Fig. 5H ) with 17–21 articles in chaetiger 20, rounded projection poorly developed; subdistal article 2–3 times longer than wide; tip falcate.

Distribution. Western Pacific Ocean, Honshu (off Kanagawa prefecture to off Mie prefecture), Japan, 230– 398 m depth.

Etymology. The species is named after the R/V Seisui -maru. The type specimens from Kumano-nada were collected by the gear of the ship. The specific name is a noun in the genitive case.

Remarks. Diplocirrus seisuiae sp. nov. resembles D. incognitus Darbyshire & Mackie, 2009 in the following features: i) body papillae are short and abundant, ii) body is covered with sediment particles, iii) lateral papillae are long, iv) anterior chaetigers are swollen, and v) gonopores are absent. Morphologically, D. seisuiae sp. nov. differs from D. incognitus by the lateral papillae in the chaetal lobe. The lateral papillae in D. seisuiae sp. nov. are almost as long as notochaetae (5/6 as long as notochaetae), whereas they are shorter (1/3 as long as notochaetae) in D. incognitus . In D. seisuiae sp. nov., the anterior part of the body (chaetigers 1–3) is covered with rusty pigments, whereas it is whitish in D. incognitus .

Figures

FIGURE 5. Diplocirrus seisuiae sp. nov. Holotype (NSMT-Pol H- 640). A, anterior end, ventral view. B, body wall, ventral view. C, dorsal branchia. D, ventral branchia. E, prostomium. F, base of notochaetae, chaetiger 21. G, tip of notochaeta, chaetiger 21. H, neurochaetae, chaetiger 21 (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 – H, 100 µm; H (insert), 20 µm.