Bradabyssa alaskensis, 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 : 29-30

Bradabyssa alaskensis n. sp.

Figure 12

Type material. Arctic Ocean, Northern Alaska . Holotype ( LACM 2598 ) and two paratypes ( LACM 2599 ), Aleutian Islands Cruise, Sta. 109 (71º34' N, 162º53' W), 140 km NNW off Icy Cape (250 km W off Point Barrow ), 42 m, silty clay sediment, 19 Aug. 1949.

Description. Body pale, cylindrical, blunt anteriorly and posteriorly, anterior end slightly everted ( Fig. 12A, B ); 36 mm long, 3 mm wide, cephalic cage 1.5 mm long, 29 chaetigers. Body papillae barely covered with fine sediment particles, forming triangular or tapered tiny lobes. Papillae short, longer than wide, tapered, slightly capitate, sometimes eroded in intersegmental areas, in 16–18 transverse series per segment in anterior chaetigers (chaetiger 10).

Anterior end observed by dissection of one paratype. Cephalic hood short, margin smooth. Prostomium low dark cone, eyes not seen. Caruncle reaching branchial plate margin, dark, lateral ridges darker, median keel pale. Palps thick, contracted, about as long as branchiae; palp lobes low, dark. Lateral lips darker, projected, dorsal and ventral lips reduced.

Branchiae cirriform, sessile on branchial plate, in two lateral groups, about 30 filaments per lateral group ( Fig. 12C ), slightly shorter than palps. Nephridial lobes not seen.

Cephalic cage chaetae as long as 1/24 body length or 1/2 body width. Only chaetiger 1 involved in cephalic cage; chaetae arranged in short lateral series, each with 2–3 chaetae.

Anterior margin of first chaetiger papillated, papillae short, abundant. Anterior chaetigers without especially long papillae. Chaetigers 1–3 becoming slightly longer. Chaetal transition from cephalic cage to body chaetae abrupt; aristate neurospines present from chaetiger 2. Gonopodial lobes in chaetiger 5, dark, cylindrical ( Fig. 12D, E ).

Parapodia well developed, lateral. Median neuropodia ventrolateral. Notopodia and neuropodia close to each other. Notopodia with chaetal lobe short, rounded, with two anterior and two posterior digitate papillae, about 1/3 as long as notochaetae; neuropodia surrounded by small, digitate papillae, most eroded, neuropodial lobes exposed ( Fig. 12F ), with 4–5 inferior elongate papillae.

Median notochaetae arranged in short transverse series, all notochaetae multiarticulate capillaries with short articles basally, medium-sized medially, longer but less defined distally ( Fig. 12G ), 4–5 chaetae per bundle, as long as 1/4 body width. Neurochaetae multiarticulate capillaries in chaetiger 1; posterior chaetigers with aristate neurospines, arranged in short transverse series, 4–5 per bundle; anterior neuropodia with rather straight neurospines ( Fig. 12H ), median and posterior chaetigers with slightly falcate neurospines ( Fig. 12I ).

Posterior end rounded, pygidium with anus terminal, anal cirri absent.

Variation. Paratypes 31–38 mm long, 3–4 mm wide, cephalic cage 1.5–2.0 mm long, 26–29 chaetigers; gonopodial lobes rounded in chaetiger 5.

Remarks. Bradabyssa alaskensis n. sp. resembles B. nuda ( Annenkova-Chlopina, 1922) n. comb. and B. strelzovi (Jirkov & Filippova in Jirkov, 2001) n. comb. by having a long, thick body and first parapodia of a similar size as the following ones. However, they differ in the relative number of chaetigers, even when of a similar size, and especially in the number of neurospines per ramus; B. alaskensis has fewer chaetigers (26–29), notochaetae (1–2), and neurospines per bundle (4–5) than the two other species. Furthermore, B. alaskensis differs from B. strelzovi in the relative size of neuropodia: in B. alaskensis they are barely projecting, whereas they are markedly projecting in B. strelzovi .

Etymology. The species name is derived from Alaska to indicate its type locality.

Distribution. Northern Alaska, Arctic Ocean, from muddy bottoms at about 50 m depth.

Figures

FIGURE 12. Bradabyssa alaskensis n. sp. A. Holotype (LACM 2598), right lateral view, tunic slightly eroded. B. Same, anterior end, lateral view (palp and branchiae slightly exposed). C. Paratype (LACM 2599), head, frontal view, palps and branchiae removed (Br: branchial scars, PS: palp scar). D. Holotype (LACM 2598), anterior end, ventral view (arrows point to everted gonopodial lobes). E. Same, close-up of left gonopodial lobe. F. Same, chaetiger 10, right parapodium, frontal view. G. Paratype (LACM 2599), chaetiger 5, right parapodium, notochaetae (insets: medial and distal regions). H. Same, neurochaetae. I. Same, chaetiger 23, right parapodium, neurochaetae. Scale bars: A: 2.5 mm, B: 0.9 mm, C: 0.6 mm, D: 1.2 mm, E: 0.3 mm, F: 0.5 mm, G: 50 µm, H: 100 µm, I: 90 µm.