Bradabyssa hartmanae, 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 : 66-67

Bradabyssa hartmanae n. sp.

Figure 33

Type material. Southern Atlantic Ocean, South Sandwich Trench. Holotype (SIORAS 866), and 8 paratypes (SIORAS 866a, ECOSUR 185), R.V. Akademik Kurchatov, Sta. 866 (55°06' S, 26°43' W → 55°06' S, 26°40' W), 7694–7934 m, Sigsbee trawl, 27 Nov. 1971 (8 complete paratypes, 8–13 mm long, 1.5–2.0 mm wide, cephalic cage chaetae 0.8 mm long, 23–30 chaetigers; gonopodial lobes in chaetiger 5; 8–12 transverse series of dorsal papillae).

Additional material. Eastern Pacific Ocean. One specimen ( LACM 9557 ), median fragment, Peru Chile Trench Expedition, R.V. Anton Bruun, Cruise II, Sta. 95 (08°31' S, 81°40' W), 4332–4423 m, Menzies trawl and beam trawl, in tandem, 15 Oct. 1965 (14 chaetigers).

Description. Holotype (SIORAS 866) complete, slightly eroded, soft, pale, most chaetae broken ( Fig. 33A ). Body elongate, slightly fusiform, 10.5 mm long, 1.5 mm wide, cephalic cage 0.5 mm long, 28 chaetigers. Tunic papillated; papillae abundant, filiform, slightly capitate, with fine sediment loosely-adhered, forming irregular globular masses, more or less fused to surrounding ones ( Fig. 33B ), individual papillae arranged in 9–10 transverse series (after sediment removal from paratypes, papillae filiform, thicker basally, about 9–10 transverse series per chaetiger). Posterior end papillae not decreasing in size towards pygidium.

Anterior end features observed in other specimens (ECOSUR 185). Prostomium low cone, pale. Eyes not seen. Caruncle poorly developed, median keel and lateral ridges low, continued posteriorly, reaching posterior margin of branchial membrane. Palps thick, large, massive, very short after contraction, slightly darker dorsally; palp keels rounded, low. Lateral lips well developed; ventral and dorsal lips reduced.

Branchiae cirriform, sessile on branchial plate, arranged as a discontinuous marginal series with four filaments per side, largest filaments dorsalmost ( Fig. 33C ). Longest filaments about one-third as long as palps. Nephridial lobes in branchial plate not seen.

Cephalic cage chaetae as long as 1/20 body length, or about 1/3 body width. Chaetiger 1 involved in the cephalic cage; chaetae arranged in short dorsoventral series; 2 notochaetae and 3 neurochaetae per fascicle; first neuropodia not projected or swollen.

Anterior dorsal margin of first chaetiger papillated, rounded. Chaetal transition from cephalic cage to body chaetae abrupt; large aristate neurospines present from chaetiger 2. Ventral gonopodial lobes not seen in holotype ( Fig. 33D ); paratypes with gonopodial lobes in chaetiger 5, each short, rounded, slightly darker than surrounding areas.

Parapodia poorly developed, chaetae emerge from body wall ( Fig. 33E ). Parapodia lateral; median neuropodia ventrolateral. Notopodia and neuropodia close to each other; short, low conical lobes, neuropodia larger.

Median notochaetae in tufts, two (rarely three) per fascicle, all multiarticulate capillaries, articulated distally, articles medium-sized, longer distally, each internally with 8–9 transverse annulations ( Fig. 33E , No); chaetae about as long as 2/3 body width. Neurochaetae multiarticulate capillaries in chaetiger 1; small aristate neurospines from chaetiger 2, larger in median neuropodia, decrease in size posteriorly, mostly 4 neurospines throughout body. Neurospines with very short rings basally and medially, distally hyaline, aristate, curved in median chaetigers ( Fig. 33E , Ne).

Posterior end tapering into rounded cone; pygidium with anus terminal, pale muscular ring (dark in some paratypes); anal cirri absent.

Variation. Paratypes 8–13 mm long, 1.5–2.0 mm wide, cephalic cage chaetae 0.8 mm long, 23–30 chaetigers.

Remarks. Bradabyssa hartmanae n. sp. is very similar to B. jirkovi n. sp. These abyssal species are the only two species in the genus that possess multiarticulate notochaetae with articles restricted only to their distal half or third. In B. hartmanae the articles are medium-sized, becoming slightly longer distally, whereas in B. jirkovi the articles are much longer throughout the whole articulated region. Most other species have only a single superior notochaetae with long articles and all the rest of the notochaetae have shorter articles. Furthermore, B. hartmanae is unique in the genus by having only eight branchial filaments.

On the other hand, as indicated above, B. hartmanae resembles what was regarded as B. “ gangetica ” because both species have notochaetae with short to medium-sized basal articles, and 9–10 series of dorsal papillae per segment. The main difference is based on dorsal papillae density and gonopodial lobe pigmentation: in B. hartmanae papillae fuse laterally and the body wall is not visible, and gonopodial lobes are indistinct from the adjacent body wall, whereas in B. “ gangetica ” papillae are distinct individually and gonopodial lobes are darker.

A posterior fragment collected in the Peru-Chile trench is regarded, with some hesitation, as conspecific because it shows similar dorsal, globose sediment balls as the type material. The neurochaetae of this Pacific Ocean specimen are slightly longer than body width, which differs from the type specimens of B. hartmanae ; the lack of the anterior end and notochaetae means that it cannot be identified with confidence.

Etymology. This species is named after the late Dr. Olga Hartman in recognition of her many publications, and because she originally proposed the genus Bradabyssa . Her series on Antarctic polychaetes have been very useful for my research.

Distribution. Southwestern Atlantic Ocean, in over 7600 m depth.

Figures

FIGURE 33. Bradabyssa hartmanae n. sp.: A. Holotype (SIORAS 866), dorsal view. B. Same, anterior end, dorsal view. C. Paratype (ECOSUR 185), prostomium with branchiae and palps removed, frontal view (1 – 4: branchial scars, PS: palp scar). D. Holotype, anterior end, ventral view. E. Paratype (ECOSUR 185), chaetiger 6, left parapodium, anterior view (No: distal notochaetal region, Ne: neurochaetal tip). Scale bars: A: 1 mm, B: 0.25 mm, C: 0.1 mm, D: 0.27 mm, E: 150 µm.