Bradabyssa mexicana, Salazar-Vallejo, 2017

Salazar-Vallejo, Sergio I., 2017, Revision of Brada Stimpson, 1853, and Bradabyssa Hartman, 1967 (Annelida, Flabelligeridae), Zootaxa 4343 (1), pp. 1-98 : 23

Bradabyssa mexicana n. sp.

Figure 9

Type material. Holotype ( LACM 7228 ), R.V. Velero IV, Sta. 7228 (27°37'17" N, 115°49'16" W → 27°30'35" N, 115°48'00" W), 62 km off Natividad Island Light , Menzies small dredge , 3726 m, 30 Dec. 1960, red and green clay, rock fragments and pebbles, ophiurans, crustaceans, echinoids. Two paratypes ( LACM 7249 ), R.V. Velero IV, Sta. 7249 (27°36'25" N, 115°56'25" W), 70 km off Natividad Island Light , Menzies small dredge , 3709 m, 4 Jan. 1961, red clay and rock.

Description. Holotype (LACM 7228) an anterior fragment, grayish, slightly depressed, previously dissected ventrally; 12 mm long, 2.5 mm wide, cephalic cage chaetae 4 mm long, mostly broken, 24 chaetigers. Body subcylindrical, tunic thick, papillated ( Fig. 9A ); body papillae digitate or capitate, mostly eroded ( Fig. 9B ), larger ones arranged into two irregular longitudinal series dorsally, four ventrally. Tunic covered with sediment particles and forminiferans dorsally, ventrally with smaller particles ( Fig. 9C ).

Cephalic hood not exposed, observed by dissection, short, smooth, margin smooth. Prostomium depressed, without eyes. Caruncle well developed, projecting posteriorly but not reaching the branchial plate posterior margin; median lobe low, lateral keels pale. Palps thick, corrugated, as long as branchiae; palp bases low, darker. Lips not projecting, distorted by dissection.

Branchiae arranged into two lateral groups, each with 4–5 concentric rows, with about 50 filaments per side ( Fig. 9D ); left group with dark pigment. Nephridial lobes not seen.

Cephalic cage notochaetae about twice as long as body width. Chaetiger 1 involved in cephalic cage, notochaetae arranged in short dorsolateral series, neurochaetae ventral; 3–4 notochaetae, 4–5 neurochaetae. Notochaetae and neurochaetae with short articles.

Anterior dorsal margin of first chaetiger conical, projecting ventrally, smooth. Anterior chaetigers without especially long papillae. Chaetigers 1–3 of similar length. Chaetal transition from cephalic cage to body chaetae abrupt; aristate anchylose neurospines start in chaetiger 4. Gonopodial lobes not seen.

Parapodia poorly developed, chaetae emerge from body wall. Parapodia lateral, median neuropodia lateral. Notopodia and neuropodia with two papillae per chaetal lobe, prechaetal ones longer, each digitate, sometimes expanded distally, longest about as long as ¼ the length of notochaetae.

Median notochaetae arranged in short oblique series, all multiarticulate capillaries with short articles basally, medium-sized medially, longer distally, 6–7 per bundle, about as long as body width. Neurochaetae multiarticulate capillaries in chaetigers 1–3, from chaetiger 4 aristate anchylose neurospines, 3–4 per bundle ( Fig. 9E ), arranged in transverse series.

Posterior end unknown.

Variation. Paratypes are anterior fragments, 2.5–10.5mm long, 0.8–2.0 mm wide, cephalic cage 1–3 mm long, 14–24 chaetigers.

Remarks. As indicated in the key above, B. mexicana n. sp. and B. indica n. sp. differ from other species in the group because both possess neurospines from chaetiger 4. They differ from each other in the relative size of cephalic cage chaetae; in B. mexicana they are only longer than body width, whereas in B. indica they are as long as the body.

Etymology. The specific name is derived from Mexico, the country in whose waters the species was found.

Distribution. Western Mexico, in mixed bottoms in water depths exceeding 3700 m.

Figures

FIGURE 9. Bradabyssa mexicana n. sp., holotype (LACM 7228). A. Dorsal view. B. Anterior end, dorsal view, bluish after methyl-green staining. C. Ventral view. D. Head, frontal view, cut open to show branchial scars, palps and branchiae removed, greenish after methyl-green staining (Br: branchial scars, PS: palp scar). E. Chaetiger 10, neurochaetae (inset: neurochaetal tips). Scale bars: A: 0.8 mm, B: 0.3 mm, C: 1.1 mm, D: 0.2 mm, E: 60 µm.