Diplocirrus glaucus (Malmgren, 1867)

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 : 9-12

Diplocirrus glaucus (Malmgren, 1867) Fig. 1

Trophonia glauca Malmgren 1867:192, Pl. 14, Fig. 78; McIntosh 1915:96-98, Pl. 96, Fig. 2, Pl. 104, Fig. 9 (syn.; simult. Haase 1915; his references stop in 1914).

Diplocirrus glaucus : Haase 1915:195-197, Textfigs. 3-5 (comb. n.); Fauvel 1927:120-121, Figs. 43 a–d; Rioja-LoBianco 1931:98-100, Pl. 30; Støp-Bowitz 1948a:25-28, Fig. 6 a–c; Hartmann-Schröder 1971:374-376, Fig. 132; Hartmann-Schröder 1996:416-417, Fig. 202; Jirkov and Philippova 2001:358-359, Figs. 1-3; Darbyshire and Mackie 2009:97, Table 1.

Stylarioides flabellata : Fauvel 1946:401 (non Sars, 1871).

Type material.

Norway. Probably lost.

Additional material.

Norway. One specimen (MNHN-A183), broken in two, without posterior end, anterior end exposed, appendices lost, Solsvick, no further data. Many specimens, Hardangerfjorden (60°10'00"N, 06°00'00"E) separated as follows: 14 anterior fragments (LACM-AHF 2620), Stat. Z20, 7 Jun. 1957, 25-16 m (up to 36 chaetigers, all with multiarticulated neurohooks; in posterior chaetigers with over 10 long articles). Two posteriorly incomplete specimens (LACM-AHF 2622), Stat. Z21, 88-78 m, 7 Jun. 1957. A mature female and a posterior fragment (LACM-AHF 2624), Stat. Z35, 98-104 m, 22 Sep. 1958 (oocytes about 125 µm). Anterior fragment, Stat. Z67, 102 m, 18 Oct. 1958. Seven specimens (LACM-AHF 2683), apparently fixed in alcohol, Stat. Z71, 102-78 m, 20 Oct. 1958 (used for details of branchiae; up to 27 chaetigers, all with multiarticulated neurohooks with articles medium-sized). Two specimens (LACM-AHF 2627), Stat. 121, 66-87 m, 15 Nov. 1958 (used for description). Faroe Islands. One specimen (MNHN-A183), anterior fragment, dige stive system mostly expulsed from the body, most chaetae broken, RV Pourquoi-Pas? Expedition, off Klaksvik (62°13'26"N, 06°34'43"W), 8-15 m, 30 Jul. 1929. Sweden. Many specimens, Tjarno (58.52°N, 11.10°E) and surroundings, Apr. 2002, L. H. Harris, coll., including: One specimen (LACM-AHF 2684) complete, light dark (24 mm long, 2 mm wide, cephalic cage 1,8 mm long, 44 chaetigers; gonad lobes in chaetigers 5 and 6). One anterior fragment (LACM-AHF 2685) with anterior end exposed (used to describe the palp bases and lips). Russia. One specimen (ECOSUR), White Sea, 60 m, 28 Jun. 1998, A. Filippova, coll. (7 mm long, 0.8 mm wide, cephalic cage 2 mm long, 21 chaetigers; papillae short, capitate). Denmark. Four specimens (USNM-332), damaged, donated by C. Lütken, id. by M. Pettibone (Most chaetae broken; slide with median and posterior chaetiger, median one is only the chaetae. Zero to one chaetae in cephalic cage. Notochaetae very thin, neurochaetae thicker, tips falcate). Germany. Two specimens (USNM-175143), North Sea, German Bight, Senckenberg Stat. 24ku, 49.2 m, 12 Aug. 1990, M. Boggemann id.

Description.

Largest specimens (LACM-AHF 2627) pale (some specimens Stat. Z71 with rusty pigmentation in chaetigers 1-3), posteriorly incomplete. Body soft, whitish (Fig. 1A, C), cylindrical, anteriorly swollen, posteriorly tapered; 17-20 mm long, 2-3 mm wide, cephalic cage 2 mm long, 23-27 chaetigers. Tunic with a thin layer of fine sediment grains, papillated. Papillae short, capitate or club-shaped, arranged in 10-12 irregular rows per segment, longer in chaetal lobes, even longer in posterior chaetigers.

Cephalic hood exposed in one specimen (Fig. 1C, LACM-AHF, Stat. 221), almost transparent, smooth. Prostomium low cone (LACM-AHF LH2-514); eyes not seen. Caruncle poorly developed, not reaching the posterior margin of branchial plate, lateral ridges low, median keel not projected (Fig 1E). Palps long, thick; palp keels rounded, reduced. Lateral lips larger, thick, dorsal lip smaller, rhomboid, ventral lip reduced, rounded. Branchiae (LACM-AHF, Stat. Z71) of two different types; posterior branchiae thicker, prismatic, laterally fused to adjacent filaments (Fig. 1B), arranged in a continuous line; anterior branchiae cirriform, slightly longer than posterior branchiae, arranged as two lateral pairs, some with a basal thickening or reinforcement, occupying about 1/6-1/7 of branchial length (Fig. 1D). Palps longer than anterior branchiae. Nephridial lobes, two pairs, placed between posterior and anterior branchiae, each short, rounded (taking methyl-green stain).

Cephalic cage chaetae as long as, or slightly longer than body width. Only notochaetae of chaetiger 1 involved in the cephalic cage, chaetae directed dorsally. Chaetae arranged in a short transverse line; 2-3 notochaetae per ramus. Anterior dorsal margin of first chaetiger papillated, papillae similar to those along the body. Chaetiger 1 short, chaetigers 2-3 longer. Post-cephalic cage chaetigers not elongated, progressively widening to chaetigers 7-8, and then tapering posteriorly. Neurohooks start in chaetiger 1. Gonopodial lobes not seen (other specimens with low, blackish, rounded spots in chaetigers 5-6).

Parapodia reduced, chaetae emerge from the body wall. Parapodia lateral; median neuropodia ventrolateral. Notopodia (Fig. 1F) and neuropodia with slightly elongated papillae in chaetal lobes. Median notochaetae arranged in a short transverse line, as long as about 1/3 body width, 7-8 per bundle; all notochaetae multiarticulated capillaries, articles medium-sized basally, slightly long medially and distally. All neurochaetae multiarticulated hooks with short articles basally, becoming longer medially, tip falcate, smooth (Fig. 1G); median neurochaetae arranged in a transverse line, 4-5 per bundle.

Posterior end tapering, blunt (LACM-AHF-LH-2-522); pygidium with anus dorsoterminal, without anal cirri. A mature female with oocytes, each about 125 µm.

Remarks.

Diplocirrus glaucus (Malmgren, 1867) is closely allied to Diplocirrus incognitus Darbyshire & Mackie, 2009 because both have swollen anterior chaetigers and some sediment particles scattered over the body. They differ in the relative size of lateral papillae and notochaetal articulation; thus, Diplocirrus glaucus has smaller papillae (up to one-fifth notochaetal length), and poorly defined basal articles in notochaetae, whereas Diplocirrus incognitus has longer papillae (up to one-third notochaetal length) and medium-sized basal articles in notochaetae.

The original description ( Malmgren 1867) indicated that the color was variable from bluish-gray to greenish or pale, but the number of chaetae in chaetiger 1 was stated as about 3, which has been used to separate it from similar species. The species was originally described from Bahusiae ( Malmgren 1867:192), corresponding with the current Bohuslan (58.88° N, 10.51° E), where the Tjarno Marine Biological Station is, and where some of the specimens used for this description were collected.

Distribution.

Northeastern Atlantic Ocean, Russian Northwestern Antarctic seas, in shallow water.