Diplocirrus longisetosus (von Marenzeller, 1890)

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 : 24-26

Diplocirrus longisetosus (von Marenzeller, 1890) restricted Fig. 7

Stylarioides longisetosus von Marenzeller 1890:5 Fig. 3, von Marenzeller 1892:426-427.

Diplocirrus longisetosus : Haase 1915:200-202, Textfigs. 6-7 (partim); Ushakov 1955:307(1965:285), Fig. 114G, H; Darbyshire and Mackie 2009:97, Table 1.

Type material.

Gulf of Alaska. Neotype (CAS-27933), and paraneotypes (CAS), off Pitt Point, Alaska, Stat. 1546 (71°19.5'N, 152°58.0'W), 55 m, sandy silt, 11 Aug. 1977, R.E. Ruff, coll. and id. (paraneotypes 10-14 mm long, 1 mm wide, cephalic cage 2.5-3.0 mm long, 25-31 chaetigers).

Additional material.

Bering Sea. Two anterior fragments (ZIRAS-27133), Providence Bay, Stat. 74 (no specific data), 18 m, mud, P. Uschakov, coll. (10.0/10.5 mm long, 2.0/2.5 mm wide, cephalic cage chaetae 3.0/2.5 mm long, 18/16 chaetigers; gonopodial lobes in chaetiger 5).

Description.

Neotype complete (CAS-27933), pale yellowish. Body club-shaped, anteriorly swollen, progressively narrowing to chaetiger 13, then cylindrical, tapering to the posterior end (Fig. 7A); 12 mm long, 1.5 mm wide, cephalic cage 2.5 mm long, 33 chaetigers. Tunic papillated, detached in several portions, with fine sediment particles. Papillae pale, cirriform, sparse, about 5-6 transverse rows in median chaetigers, slightly longer dorsally; in median chaetigers about 1/5 as long as notochaetae.

Anterior end modifications observed in a paraneotype. Cephalic tube short, smooth, margin apparently smooth. Prostomium low, pale, eyes black, small. Caruncle not seen. Palps pale, thick, deeply furrowed, as long as branchiae; palp keels reduced. Lips damaged by dissection. Branchiae thick, cirriform, sessile on branchial plate; posterior branchiae thicker, anterior branchiae cirriform, two thinner filaments per lateral group. Nephridial lobes very thin, long, placed below the posterior row central filaments.

Cephalic cage chaetae 1/5 as long as body length, or 2/3 as long as body width. Chaetigers 1-2 involved in the cephalic cage; chaetae arranged in short, dorsolateral lines, 5(-8) noto- and 5 neurochaetae per bundle. Anterior dorsal margin of first chaetiger papillated; anterior chaetigers without especially long papillae. Chaetigers 1-3 progressively larger. Post-cephalic cage chaetigers not elongated. No chaetal transition from cephalic cage to body chaetae, all neurochaetae similar. Gonopodial lobes present in chaetiger 5, low, round, pale lobes, covered by small papillae, difficult to be seen even after methyl green staining (Fig. 7B).

Parapodia lateral, poorly-developed, chaetae emerge from the body wall (Fig. 7C); median neuropodia ventrolateral. Notopodia 1-2 with low, conical, chaetal lobes directed forward, remaining parapodia without conical lobes. Neuropodia 1-4 with low, conical chaetal lobes. Noto- and neuropodia distant to each other.

Median notochaetae arranged in a transverse horizontal C-shaped pattern; all notochaetae multiarticulated capillaries, short articles basally, medium-sized medially, long distally (Fig. 7D). About 11(-13) chaetae per bundle, twice as long as body width. All neurochaetae multiarticulated capillaries, very short articles basally, well-defined, medium-sized medially, long distally (Fig. 7E); tips straight; arranged in a transverse line, 8-9 per bundle.

Posterior end tapering to a rounded lobe; pygidium with anus terminal, without anal cirri.

Neotype locality.

Off Pitt Point, Alaska, 55 m, sandy silt.

Remarks.

As currently restricted, Diplocirrus longisetosus (von Marenzeller, 1890),closely resembles Diplocirrus micans Fauchald, 1972 and Diplocirrus normani (McIntosh, 1908), comb. n. These species have notochaetae longer than the body width, and long papillae with out sand particles, although Diplocirrus micans separates from the other two species by having neurochaetae with long articles, and because it lacks gonopodial lobes. Then, Diplocirrus longisetosus and Diplocirrus normani differ especially in the relative body color, papillae and gonopodial lobes, and on the relative resolution of neurochaetal basal articles. In Diplocirrus longisetosus , papillae and gonopodial lobes are pale, and basal neurochaetal articles are well-defined, whereas in Diplocirrus normani , the body is grayish, and papillae and gonopodial lobes are darker or blackish, whereas neurochaetal basal articles are poorly-defined.

Further, Diplocirrus longisetosus was described from Providence Bay, Russia, in the Bering Sea, with a single anterior fragment. Haase (1915:200) studied the supposed holotype (which is now lost), an additional specimen sent him by von Marenzeller, probably coming from Spitzbergen, Norway, and an additional broken specimen. This combination resulted in a mixture of morphological features and the species has been recorded from several localities in the Arctic Ocean as well as in the Northern Atlantic and Northern Pacific. Consequently, a redescription and proposal of a neotype is needed to clarify if there is more than one species. Støp-Bowitz (1948:32) noticed the nephridial lobes in the branchial plate, but he regarded them as accessory branchiae.

After the International Code of Zoological Nomenclature (1999, Art. 75), a neotype is being designated because there is no name-bearing type specimen, and because of the confusion between the above two species requires a designation to objectively define Diplocirrus longisetosus . Consequently, in order to satisfy the qualifying conditions (Art. 75.3), it must be stated that this designation will clarify the taxonomic status, a description and illustrations have been presented to ensure the recognition of the species. Further, collection managers in several German museums were contacted in order to find the type material for this species, but none exists. On the other hand, the neotype fits the characteristics originally noticed in the species, it was found in a locality with ecological conditions similar to the ones prevailing in the original type locality, and has been deposited in the California Academy of Sciences.

Distribution.

Originally described from Providence Bay (64°30'N, 173°30'W), Russia, these specimens come from Northern Alaska, about 1,200 km away, but despite the distance between them, these localities share the same environmental conditions, and the incomplete topotype specimens have most of the same morphological features.