Diplocirrus nicolaji (Buzhinskaja, 1994) Buzhinskaja, 1994

Salazar-Vallejo, Sergio I. & Buzhinskaja, Galina, 2011, Revision of Diplocirrus Haase, 1915, including Bradiella Rullier, 1965, and Diversibranchius Buzhinskaja, 1993 (Polychaeta, Flabelligeridae), ZooKeys 106, pp. 1-45 : 28-30

Diplocirrus nicolaji (Buzhinskaja, 1994) comb. n. Fig. 9

Diversibranchius nicolaji Buzhinskaya 1994:231, Figs. 2-7; Darbyshire and Mackie 2009:97, Table 1.

Flabelligeridae from Japan: Rouse and Pleijel 2001, Plate 11, Fig. f.

Type material.

Northwestern Sea of Japan. Holotype (ZIRAS-48504), Vostok Bay (42°30'N, 133°00'E), Peter the Great Bay, Russia, 7 m, muddy sand, 26 Oct. 1989, G. Buzhinskaja, coll. Several paratypes (ZIRAS-48506), five anterior fragments (four with anterior end exposed, variously damaged), and several median fragments, Vostok Bay (42°50'N, 132°45'E), Peter the Great Bay, Russia, 7 m, muddy sand, 26 Oct. 1989, sample 2, G. Buzhinskaja & S. Kiyashko, coll. (anterior fragments 5.5-12.0 mm long, 0.7-2.0 mm wide, 12-24 chaetigers, chaetiger 1 notochaetae 0.3-0.6 mm, 10-22 transversal rows of papillae, gonopodial pores in chaetigers 3 –7(– 8, 9, 14 one each). Five paratypes (ZIRAS-48507), Vostok Bay (42°50'N, 132°45'E), Peter the Great Bay, 3m, muddy sand, 21 Sep. 1989, G. Buzhinskaja, coll. (6-9 mm long, 0.6-1.0 mm wide, 10-18 chaetigers, chaetiger 1 notochaetae 0.4-0.5 mm, 12-20 transversal rows of papillae, gonopodial pores in chaetigers 3 –9(– 10 in 2 paratypes, -11 in one; gut sediment particles heterogeneous, up to 0.6 mm long).

Additional material.

Northwestern Pacific Ocean. Northwestern Sea of Japan, Peter the Great Bay, Russia. One specimen (ZIRAS-2/48505), Vostok Bay (42°50'N, 132°45'E), 7 m, muddy sand, 26 Oct. 1989, G. Buzhinskaja, coll. Five specimens (ZIRAS-3/48506), one beheaded, Vostok Bay (42°50'N, 132°45'E), 7m, muddy sand, 26 Oct.1989, G.Buzhinskaja & S.Kiyashko, coll. Five specimens (ZIRAS-4/48507), Vostok Bay (42°50'N, 132°45'E), 3m, muddy sand, 21 Sept.1989, G.Buzhinskaja, coll. One specimen (ZIRAS-5/48508), beheaded, Posyet Bay (42°30'N, 131°00'E), 3 m, muddy sand, among Zostera asiatica , diving, sample from 0.25 m2, 10 Mar. 1966, A.N. Golikov, coll. Three anterior fragments (ZIRAS-6/48509), beheaded, Tikhaya Bay, Posyet Bay (42°30'N, 131°00'E), 3m, muddy sand, among Patiria pectinifera and Chaetopterus , 3 Mar. 1966, diving, sample from 0.1 m2, A.N. Golikov, coll. One specimen (ZIRAS-7/48510), Tikhaya Bay, Posyet Bay (42°30'N, 131°00'E), 4-5 m, muddy sand, among Patiria pectinifera and Chaetopterus , 21 Apr. 1965, diving, sample from 0.3 m2, L. Chislenko, coll.

Description.

Holotype (ZISP-48504) orange yellow, slightly macerated, without posterior end. Body anteriorly swollen, posteriorly tapering; 19 mm long, 1.9 mm wide, no cephalic cage (chaetiger 1 notochaetae 0.3 mm), 30 chaetigers. Tunic densely covered by papillae (Fig. 9A, C, E); papillae short, most 8-shaped, others digitate, with fine sediment adhered to their base, about 12 rows per segment.

Cephalic hood exposed, as long as the following 4 chaetigers, with small, sparse papillae, cephalic hood margin smooth. Prostomium low, eyes not seen. Palps thick, slightly longer than branchiae; palp lobes reduced, rounded. Other features from paratypes. Caruncle projected dorsally to the base of posterior branchiae, tapering, lateral lobes elevated, posteriorly fused. Dorsal lip projected, lateral lips thicker, ventral lip reduced. Nephridial lobes in branchial plate not seen (Fig. 9B).

Branchiae of two different types (Fig. 9A, B). Posterior row with four prismatic, thicker, lamellate branchiae, lamella reaching the tips; lateral branchiae of the same size, with dorsal keel rounded, reduced, with longitudinal bands and laterally expanded dorsal surface, with a thin axis, branchial lateral margins with two rounded, sucker-like sockets; median branchiae with dorsal keel as those present in lateral branchiae, not foliose, corrugated. All posterior branchiae with a series of successive transverse blades on their ventral side; in median branchiae, all laterally fused making a single convoluted blade; in lateral branchiae the transverse blades laterally free. Anterior row with four thin, cirriform branchiae, shorter than palps, arranged in two lateral pairs, each filament with a convoluted lamella along its basal third, and successive ciliary bands medial- and distally. Interbranchial lobes small, between median and lateral branchiae (dorsal), and outside the lateral ones (lateral); dorsal lobes small, rounded, lateral lobes rounded, slightly larger).

First chaetiger displaced dorsally, notochaetae slightly longer than following ones. Notochaetae arranged in a short, oblique line with 2 multiarticulated hooks. Anterior dorsal margin of first chaetiger papillated, as following segments; no other modification. Anterior chaetigers without longer papillae, chaetiger 1 shorter than following ones, chaetal lobes lateral, very close to each other. Chaetigers 5-10 swollen, without marked segmentation between them; therafter segments better defined. Gonopores orange-red, in chaetigers 2-12 (Fig. 9C, D).

Parapodia poorly developed; chaetae emerge from the body wall (Fig. 9F). Notopodia and neuropodia with papillae as long as the others. Noto- and neuropodia close to each other. Notochaetae multiarticulated capillaries, all articles long (Fig. 9G). Median notochaetae arranged in a longitudinal line, with 4 per bundle in holotype (11 per bundle in larger; 6-7 in smaller specimens), longest about as long as one-third body width. Median neuropodia lateral, very close to notopodia. Neurochaetae multiarticulated hooks from chaetiger 1 (Fig. 9G), arranged in a short longitudinal line (J-pattern in other specimens), 3-4 per bundle (6-8 in other specimens), each with long articles of about the same length, distal article falcate, finely transversely divided, not articulated, with a hood-like membrane.

Posterior end missing in holotype (probably invaginated); a posterior fragment (ZISP-48507, Fig. 9E) tapering to a rounded lobe; pygidium with anus dorsoterminal, dark, muscular, without anal cirri.

Variation.

Living specimens dark-orange, gills green. The paratypes were orange-yellow to orange-brown, with 29-31 chaetigers.

Remarks.

Diplocirrus nicolaji (Buzhinskaja, 1994), comb.n. is closely allied to Diplocirrus branchiatus (Rullier, 1965) because the bodies of these species lack sediment particles, have ventrolateral gonopores in some anterior chaetigers, reduced chaetae in the first chaetiger, and their caruncles taper posteriorly. Their main differences rely on the relative neurochaetal development in median chaetigers, and on the area covered by lamellae in the cirriform branchiae; thus, Diplocirrus nicolaji has barely tapering neurochaetae, with some 10 articles of about the same length, tips markedly falcate, and their cirriform branchiae has a lamellate region extending up to one-third of the branchial length, whereas in Diplocirrus branchiatus , the neurochaetae are tapering, provided with about 23 articles, decreasing in size distally, tips delicately falcate, and the lamellate region along cirriform branchiae might reach one-fifth of the branchial length.

Distribution.

Originally described from Vostok Bay, Peter the Great Bays, Northwestern Sea of Japan, in shallow water soft bottoms (3-7 m).