Flabegraviera fujiae, Jimi, Naoto, Tsujimoto, Megumu, Watanabe, Kentaro, Kakui, Keiichi & Kajihara, Hiroshi, 2017

Jimi, Naoto, Tsujimoto, Megumu, Watanabe, Kentaro, Kakui, Keiichi & Kajihara, Hiroshi, 2017, A new species and the shallowest record of Flabegraviera Salazar-Vallejo, 2012 (Annelida: Flabelligeridae) from Antarctica, Zootaxa 4221 (4), pp. 477-485 : 478-481

Flabegraviera fujiae sp. nov.

(New Japanese name: Fuji-kibukure-habouki) ( Figs 1–2 )

Type material. Holotype. NSMT-Pol-H-609. Complete (some chaetae broken, dissected), sex undetermined, nonreproductive-adult, Nishinoura (69°00.4´S, 39°34.5´E), 9 m depth, sandy mud, 16 Jan., 1981.

Description. Holotype (NSMT-Pol-H-609) 9.4 cm long, 1.8 cm wide. Body fusiform, covered by very thick tunic ( Fig. 1 A). Tunic transparent, gel-like, covering whole body except cephalic cage (partially eroded); sediment grains attached dorsally, ventrally, and laterally (size in long axis ~40 µm), not immersed in tunic. Body papillated; papillae long, clavate, forming sheath covering chaetae, mostly eroded. Lobe on dorsum of chaetiger 1 absent. Dorsal and ventral surface irregular.

Prostomium low cone. Branchiae 6–8 rows, about 110 filaments per side, 3–5 mm long, decreasing in size ventrally, black in ethanol. Branchial plate crescent-like, bisected by well-developed caruncle ( Fig. 1 B). Palps long (6 mm), cylindrical, pink in ethanol. Four black eyes present. Lateral and dorsal lips well developed; ventral lip reduced. Nephridial lobes present.

Chaetigers 33 in number; chaetiger 1 comprising cephalic cage. Cephalic cage 1.6 cm long, exposed whole, about 1/5 body length (9/10 body width), comprising 39 notochaetae and 24 neurochaetae per side. Chaetal transition from cephalic cage to body abrupt.

Parapodia well developed, completely covered by tunic, notopodia and neuropodia widely separated. Gonopodial lobe absent.

Chaetal bundles arranged into a straight series not like F. mundata . Notochaetae of two types: 1) multiarticulated, 1.2–3.4 cm long, 5–7 per fascicle ( Fig. 2 A); and 2) not multiarticulated, 3 mm long, 8–10 per fascicle ( Fig. 2 B). Neurochaetae multiarticulated capillaries in chaetiger 1. Neurohooks in chaetigers 2–33 ( Fig. 2 C, D), 3–5 per fascicle, anchylosed, 0.7–0.9 cm long, pale orange, covered by a cylindrical shaft; crest bending region anchylosed. Multiarticulated neurohooks absent.

Posterior end exposed, truncate; last two segments achaetous; pygidium simple; no anal cirri; anus without pigment ( Fig. 1 C).

Etymology. The species is named after the Japanese icebreaker Fuji, utilized for the research operation during which KW collected the holotype. The derivation is made after the vessel’s name taken as a feminine proper name. The new specific name is thus a noun in the genitive case. The Japanese name literally means ‘Fuji’s thickly dressed flabelligerid’, derived from kibukure (thick-dressed) and haboukigokai (flabelligerid polychaete).

Remarks. Morphologically, Flabegraviera fujiae sp. nov. resembles Flabegraviera profunda Salazar-Vallejo, 2012 because in both species the notochaetal arrangement follows a straight-line, the neurohooks are anchylosed, and the tunic carries sediment grains. However, F. fujiae can be discriminated from F. profunda by the relative size and exposure of the cephalic cage, which is exposed almost entirely in F. fujiae , whereas it is covered by the tunic in F. profunda . In addition, the cephalic cage is about 1/5 body length in F. fujiae , compared to about 1/ 10 in F. profunda . An additional difference is that F. fujiae has eyes. Our specimen was collected from a depth of 9 m, that is markedly shallower than the previous records for F. profunda , collected in sediments at 330–450 m water depth ( Salazar-Vallejo 2012).

Figures

FIGURE 1. Flabegraviera fujiae sp. nov., holotype, NSMT-Pol-H- 609. A, Entire body, body twisted, anterior region in lateral view, posterior region in ventral view; head upper side; B, Head, frontal view; left half of branchial plate has been partly removed; branchiae and palps have been removed (BP, branchial plate; Ca, caruncle; LL, lateral lip; PS, palp scar); C, Posterior end, ventral view; arrow indicates ventral anal margin. Scale bars = 10 mm (A); 1 mm (B, C).

FIGURE 2. Micrographs of chaetae in Flabegraviera fujiae sp. nov., holotype, NSMT-Pol-H- 609. A, Chaetiger 29, tip of notochaeta; B, Same, base of notochaeta; black arrows indicate type 2 notochaetae; C, Chaetiger 6, tip of smaller neurohook; D, Chaetiger 27, tip of neurohook. Scale bars = 50 µm (A); 200 µm (B); 100 µm (C, D).