Diplocirrus hirsutus (Hansen, 1878)

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 : 19-21

Diplocirrus hirsutus (Hansen, 1878) Fig. 4

Trophonia hirsuta Hansen 1878:9-10, Pl. 7, Figs. 1-4; Hansen 1882:38, Pl. 7, Figs. 5-8.

Stylarioides hirsutus : von Marenzeller 1889:129-130 (comb. n.); Ditlevsen 1911:426, Pl. 29, Fig. 11, Pl. 31, Figs. 23, 24.

Diplocirrus hirsutus : Haase 1915:198-200 (comb. n.); Støp-Bowitz 1948a:28-30, Fig. 7, Støp-Bowitz 1948b:37-38, map; Wesenberg-Lund 1950:35; Fauchald 1972:412; Jirkov and Philippova 2001:359, Figs. 1-7; Darbyshire and Mackie 2009:97, Table 1.

Type material.

Norway. Syntypes (ZMUB-2287), four anterior fragments and a dissected anterior end, two previously dissected, NMH Expedition, Stat. 18 (62°44'N, 01°48'E), and Stat. 31 (63°10'N, 05°00'E) (syntypes yellowish, incomplete, 4-5 n otochaetae in chaetiger 1; 8-9 notochaetae in median chaetigers; 10 transversal rows of papillae in chaetiger 10; gonopodial lobes not visible).

Additional material.

Norway. Two specimens (ZMUB-25216), Norkse Nordhavs. Expedition, Stat. 262 (no data) (two anterior fragments, dried out). Five specimens (ZMUB-27459), NMH (N. Nordhosk Expedition, Stat. 326 (no data), Hansen, coll. (complete 19-22 mm long, 2.5-2.7 mm wide, cephalic cage 2.0-2.5 mm long, 29-37 chaetigers; gonopodial lobes in chaetigers 5-6 in two specimens).

Description.

Larger syntype pale, soft, yellowish (Fig. 4A, B). Body club-shaped, swollen anteriorly, progressively narrowing to chaetiger 12, then cylindrical to the end of the fragment (and body; Fig. 4C)); 10 mm long, 3.5 mm wide, cephalic cage chaetae 2 mm long, 20 chaetigers. Tunic papillated, fine sediment particles on papillae basis only (other specimens with sediment cover towards the tip). Papillae long, abundant, capitate, with basal sediment making a rounded lobe (Fig 4B), about 10 transverse rows in chaetiger 10, much longer dorsally, longest about 2/3 as long as notochaetae.

Anterior end observed in a previously dissected specimen and in non-type specimen. Cephalic hood short, smooth, margin smooth. Prostomium low cone, grayish, eyes barely pigmented (Fig. 4E), difficult to be seen in syntype or non-types. Caruncle not observed in syntype, weakly defined in non-types. Palps thick, longer than the only available cirriform branchia; palp bases rounded, projected. Lateral lips projected, thick, well-developed, dorsal and ventral lips reduced. Branchiae mostly lost, scars remain; posterior row with thicker scars, anterior row with a single cirriform branchiae without basal blades (all cirriform, posterior ones slightly thicker, smooth). Nephridial lobes rounded, elevated, separating anterior and posterior branchial rows (taking methyl green stain deeply).

Cephalic cage chaetae shorter than body width. Chaetiger 1 involved in the cephalic cage, chaetae arranged in short dorsolateral lines, with 4-5 noto- and 9-10 neurochaetae per bundle. Anterior dorsal margin of first chaetiger papillated; anterior chaetigers with papillae longer than those present in following chaetigers. Chaetigers 1-3 progressively longer. No chaetal transition from cephalic cage chaetae to body chaetae; all neurochaetae multiarticulate falcigers but first chaetigers with shorter articles. Gonopodial lobes not seen in syntypes (oval, bare, pale areas in chaetigers 5-6 in non-types; Fig. 4D).

Parapodia lateral, poorly developed, chaetae emerge from the body wall; median neuropodia ventrolateral. Notopodia without conical lobes. Noto- and neuropodia distant to each other.

Median notochaetae arranged in a longitudinal, transverse, short line; all notochaetae multiarticulated capillaries (Fig. 4F), medium-sized articles basally, longer medial- and distally; 8-9 notochaetae per bundle in median chaetigers (up to 14 in non-types), about as long as body width. All neurochaetae multiarticulated hooks, markedly tapering subdistally (Fig. 4F); basal articles short, ill-defined, longer medial- and distally, but diminishing in size towards the tip, 5-6 per bundle.

Posterior end, observed in non-type specimens, truncate (Fig. 4C); pygidium with anus terminal, without anal cirri.

Remarks.

Diplocirrus hirsutus (Hansen, 1878) resembles Diplocirrus longisetosus (von Marenzeller, 1890) and Diplocirrus normani (McIntosh, 1908), comb. n. because they have bodies provided with long papillae but without sand particles. Their main difference lies in the relative length of notochaetae in median chaetigers, because the latter two species have notochaetae markedly longer than body width, whereas in Diplocirrus hirsutus they are about as long as body width.

Haase (1915:199) noticed the cinnamon-red color for specimens of this species. The available specimens show a concentration of the pigment towards the anterior end, making a thin crust surrounding papillae and chaetae. Thus, it is not the basic color of the organism but rather some adsorbed minerals on these structures and, whenever this pigmentation is present, chaetae are darker, which indicates that the minerals are either ingested and later used for chaetal formation, or adsorbed to chaetae as well as over the tunic. This pigmentation should rely on the minerals available in the sediments, and therefore should not be used as a diagnostic feature.

Distribution.

Originally described from Norway, it ranges in Arctic and Subarctic environments in shallow water. The Antarctic records by Hartmann-Schröder and Rosenfeldt (1989:71-72; 1991:74-75) are questionable.