Diplocirrus asamushiensis, 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 asamushiensis sp. nov.

(New Japanese name: Asamushi-konbou-habouki) ( Figure 1 )

Type materials. Holotype: NSMT-Pol H-633, Asamushi, 2–5 m depth, collected by NJ, COI sequence DDBJ accession no. LC314563 . Paratypes: NSMT-Pol P-634, Asamushi, 2–5 m depth, collected by NJ, one complete specimen (28 mm long, 1.8 mm wide, 39 chaetigers) and two incomplete specimens (14–20 mm long, 1.6–1.7 mm wide, 15–27 chaetigers).

Description. Holotype incomplete, 18 mm long, 1.8 mm wide (in chaetiger 10), 24 chaetigers. Body with first 13 chaetigers swollen, thereafter cylindrical ( Fig. 1A ). Tunic whitish in ethanol with sediment particles on base of papillae only ( Fig. 1B ). Digitate papillae abundant, white to brown, longer than wide, short, in median chaetigers about 3/20 as long as notochaetae and as long as lateral papillae in chaetal lobe, arranged in 10–12 transverse rows per segment. Cephalic hood transparent, with papillae near 1 st chaetiger . Gonopodial lobes not seen. Gonopores in chaetigers 3–9, pale brown ( Fig. 1B ). Posterior region tapered, anal part lost in holotype (no anal cirri in paratypes).

Two types of branchiae present: dorsal branchiae 1.5 mm long, thick, with one lobe in internal side, not lamellate ( Fig. 1C ); ventral branchiae 2 mm long, thin, smooth, not lamellate ( Fig. 1D ). Palps 3 mm long, grooved. Upper and lateral lips well developed. Caruncle projected, not separating dorsal branchiae ( Fig. 1E ). Eyes absent. Nephridial lobes present.

Parapodia poorly developed, chaetae emerging from body wall; lateral papillae in chaetal lobes as long as other body papillae. Cephalic cage poorly developed (1 st notochaeta 0.2 mm in length). Notochaetae 4–7 per bundle, multiarticulate ( Fig. 1F ) with 34–37 articles in chaetiger 24; tip smooth. Neurochaetae 2–3 per bundle, multiarticulate ( Fig. 1G ) with 7–9 articles in chaetiger 24, rounded projection poorly developed; subdistal article 5–6 times longer than wide; tip falcate.

Distribution. Only known from the type locality (Asamushi); 2–5 m depth.

Etymology. This species is named after the type locality (Asamushi). The specific name is an adjective.

Remarks. Diplocirrus asamushiensis sp. nov. resembles D. nicolaji and D. mamoi sp. nov. in the following features: i) the body papillae are abundant and short, ii) sediment particles are attached only on the base of papillae, iii) the cephalic cage is poorly developed, and iv) the number of the neurochaetal articles is less than 22 in median chaetigers. These three species are discriminated by the three features: branchial forms, caruncle length, and number of neurochaetal articles. Both of the two types of branchiae in D. asamushiensis sp. nov. and D. mamoi sp. nov. are smooth, whereas they are lamellate in D. nicolaji . The dorsal branchiae of D. asamushiensis sp. nov. are shorter than the ventral ones, whereas they are as long as ventral ones in D. mamoi sp. nov. The number of the median neurochaetal articles in D. asamushiensis sp. nov. ranges from seven to nine, whereas it is 5–6 in D. mamoi sp. nov. Subdistal article of D. asamushiensis sp. nov. is 5–6 times longer than wide, whereas it in D. mamoi sp. nov. is 8–9 times longer than wide.

Figures

FIGURE 1. Diplocirrus asamushiensis sp. nov. Holotype (NSMT-Pol H- 633). A, anterior end, lateral view. B, body wall, ventral view; arrow indicates gonopore. C, dorsal branchia. D, ventral branchia. E, prostomium. F, notochaetae, chaetiger 25. G, neurochaetae, chaetiger 25. Abbreviations: BS, branchial scar; Ca, caruncle; LL, lateral lip; NL, nephridial lobe; PS, palp scar. Scale bars: A, 5 mm; B, 250 µm; C – E, 500 µm; F – G, 100 µm.