Bradabyssa nuda Salazar-Vallejo 2017, n. comb.

Bradabyssa nuda (Annenkova-Chlopina, 1922) n. comb.

Figure 16

Brada nuda Annenkova-Chlopina, 1922: 40.— Ushakov 1955: 309 (1965: 287), Fig. 115M.— Levenstein 1966: 45.— Jirkov & Filippova 2001: 354.

Brada villosa.— Okuda 1937: 53 –54, Pl. 2, Fig. D.— Pettibone 1954: 290 –291.— Ushakov 1955: 311 (1965: 289), Fig. 115D–H.— Imajima & Hartman 1964: 302.— Imajima 2011: 193 (non Rathke, 1843).

Type material. Arctic Ocean, Chukchi Sea. Syntypes of Brada nuda Annenkova-Chlopina, 1922: four complete specimens and an anterior fragment (ZIRAS 26637), damaged, R.V. Vaigach, Sta. 125 (67°00' N, 168°40' W), 50 m, trawl, muddy sand, 15(28) Sep. 1910, É.E. Arngold, coll. (21–33 mm long, 4–6 mm wide, cephalic cage 1.0– 1.5 mm long, 35–40 chaetigers, gonopodial papillae in chaetiger 5; 10–14 series of papillae in chaetiger 10, slightly more abundant in larger specimens), and five complete specimens (ZIRAS 26638), herein used for description, Chukchi Sea, R.V. Vaigach, Sta. 155 (67°59' N, 169°17' W), 55 m, trawl, muddy sand, 7(20) Sep. 1911, É.E. Arngold, coll.

Additional material. Arctic Ocean, Beaufort Sea. One specimen (LACM 47), complete, Cruise WEBSEC 71, R.V. Glacier, unnumbered station (71º01.0' N, 148º22.7' W), 70 km N off Prudhoe Bay, Alaska, 47 m, 31 Aug. 1971 (24 mm long, 2.8 mm wide, cephalic cage 2 mm long, 37 chaetigers; gonopodial lobes in chaetiger 5). Two specimens (LACM 48), one without posterior region, Cruise WEBSEC 71, R.V. Glacier, unnumbered station (70º27' N, 143º34' W), 40 km N off Barter Island, Alaska, 48 m, 20 Aug. 1971 (complete 34 mm long, 4.5 mm wide, cephalic cage 1.5 mm long, 33 chaetigers; gonopodial lobes in chaetiger 5; incomplete 43 mm long, 5.5 mm wide, cephalic cage 2 mm long, 31 chaetigers; gonopodial lobes in chaetiger 5). Two specimens (LACM 57), complete, Cruise WEBSEC 71, R.V. Glacier, un-numbered station (70º44' N, 145º52' W), 60 km N off Flaxan Island, Alaska, 57 m, 22 Aug. 1971 (27–39 mm long, 4.0– 4.5 mm wide, cephalic cage 2 mm long, 37–39 chaetigers; gonopodial lobes in chaetiger 5). Canada. One specimen (USNM 1422404), Cambridge Bay, Wellington Bay, Victoria Island, Sta. 7015 (69º24.3' N, 106º19.5' W), 23 m, mud, 9 Aug. 1962, E.H. Grainger, coll. (24 mm long, 3 mm wide, cephalic cage 1 mm long, 35 chaetigers).

Description. Complete syntypes (ZIRAS 26638), pale, anteriorly blunt (Fig. 16A, C), tapered posteriorly; 32–39 mm long, 6 mm wide, cephalic cage 1.5–2.0 mm long, 37–40 chaetigers. Papillae mostly without sediment, but some sediment basally adhered. Papillae elongate, cylindrical, appearing fusiform, slightly capitate, not covering intersegmental areas, in 13–18 series in anterior chaetigers (chaetiger 10), not more abundant in larger specimens but in about 10–14 in smaller specimens.

Anterior end observed in another specimen (Fig. 16B). Cephalic hood short, margin smooth. Prostomium low, dark; eyes not seen. Caruncle short, reaching branchial plate margin, pale, lateral lobes pale, low, median keel darker, thin perhaps due to contraction. Palps pale, thick, as long as branchiae; palp keels projecting. Lateral lips well developed, ventral and dorsal lips reduced.

Branchiae pale, cirriform, sessile on branchial plate, arranged in concentric series with longest filaments as long as palps, decreasing in size laterally, about 60 filaments per group. Nephridial lobes dark, lobate, thicker than nearby branchial filaments, present on ventrolateral margin of branchial plate.

Cephalic cage present, chaetae as long as 1/19 body length or 1/3 body width. Only chaetiger 1 involved in the cephalic cage; chaetae arranged in short lateral series, each with 3–4 chaetae.

Anterior margin of first chaetiger papillated, papillae very long, abundant (eroded in other specimens). Anterior chaetigers without especially long papillae. Chaetigers 1–3 of similar length. Chaetal transition from cephalic cage to body chaetae abrupt; aristate neurospines present from chaetiger 2. Gonopodial lobes in chaetiger 5, digitate, wider basally, tapered into blunt tips (Fig. 16C).

Parapodia well developed, lateral. Median neuropodia ventrolateral. Notopodia and neuropodia close to each other. Notopodia with chaetal lobe rounded, with 2 inferior long papillae, about 1/4 as long as notochaetae; neuropodia with larger rounded lobe, with 4–5 inferior long papillae; notopodial lobes rounded, short.

Median notochaetae arranged in short transverse series, all notochaetae multiarticulate capillaries with articles short basally and medially, slightly longer distally, 5–6 chaetae per bundle (Fig. 16E), as long as 1/4 body width. Neurochaetae multiarticulate capillaries in chaetiger 1; following chaetigers with aristate neurospines, arranged in short transverse series to chaetiger 9, then in J-shaped pattern to chaetiger 18, following chaetigers with neurochaetae in horizontal-shaped patterns, 6–7 per bundle. Each neurospine with rings short basally and medially, distally smooth, hyaline, with long aristae (Fig. 16F).

Posterior end rounded, pygidium with anus terminal, anal cirri absent (Fig. 16D).

Variation. Complete specimens 21–39 mm long, 4–6 mm wide, cephalic cage 1–2 mm long, 33–40 chaetigers.

Remarks. Bradabyssa nuda (Annenkova-Chlopina, 1922) n. comb. resembles B. alaskensis n. sp. and B. strelzovi (Jirkov & Filippova in Jirkov, 2001) n. comb. by having a large, thick body and first parapodia of similar size to following ones. However, B. nuda differs from the other two species because its gonopodial lobes are midventrally displaced, as they are set at a greater distance from neuropodia than the corresponding gonopodial length. The records of B. villosa from the Northwestern Pacific Ocean could correspond to B. nuda.

Distribution. Arctic Ocean and Northwestern Pacific Ocean, in 50–55 m depth.