Bradabyssa kirkegaardi, 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 : 72-74

Bradabyssa kirkegaardi n. sp.

Figure 37

Ilyphagus bythincola .— Kirkegaard 1956: 70, Fig. 9 .—Levenstein 1961b: 138, map (non Chamberlin, 1919).

Type material. Eastern Indian Ocean. Holotype ( ZMUC 1781 ), off southern Java, Sunda Trench , R.V. Galathea, Sta. 462 (10°02' S, 107°52' E), 6730 m (depth follows the publication), 9 Mar. 1952 .

Additonal material. Central Western Pacific Ocean, off New Ireland ( Papua New Guinea). One specimen, poorly preserved ( SMF 15324), R.V. Sonne, cruise 133, Sta. 65-GKG, NE of Lihir (02°38.964' S, 153°01.926' E), 2040 m , 28 Jul. 1998 (4 mm long, 1 mm wide, cephalic cage 0.5 mm long (most broken off), 12 chaetigers; gonopodial lobes not seen). Tasman Sea, SW Pacific Ocean , off Southern New Zealand. One specimen ( SMF), R.V. Sonne, cruise 136, Sta. 62-EBS (53°19.04' S, 169°11.34' E), 628–632 m , 26 Oct. 1998 (6.8 mm long, 1.8 mm wide, cephalic cage 1.3 mm long, 22 chaetigers; gonopodial papillae not seen; 4–5 transverse series of papillae). One specimen and fragments ( SMF 15325), R.V. Sonne, cruise 136, Sta. 2-EBS (42°17.65' S, 169°56.05' E), 937–945 m , no date (4.5 mm long, 0.8 mm wide, cephalic cage chaetae 0.8 mm long, 22 chaetigers; gonopodial lobes not seen). One specimen, poorly preserved (SIORAS 4535), R.V. Vitjaz, Sta. 4535 (10°08' S, 107°55' E), Java Trough, 6850 m .

Description. Holotype (ZMUC 1781) complete, slightly damaged, soft, whitish ( Fig. 37A ), two parapodia previously removed, anterior end everted. Body slightly fusiform, 8 mm long, 2 mm wide, cephalic cage 1.5 mm long, 19 chaetigers. Tunic papillated, mostly free from sediment coverage; papillae sparse, cylindrical, very long, with sediment adhered, especially basally, more eroded ventrally ( Fig. 37B ). Posterior end papillae very long.

Cephalic hood tube thin, short; cephalic hood margin smooth (partialy eroded). Prostomium reduced, without eyes; caruncle not seen. Palps thick, rounded, pale (one left); palp keels reduced. Lips and branchiae not seen (two specimens SMF 15325, dissected; poorly preserved, 10 branchial filaments in single row, middorsal ones longer; other features unknown).

Cephalic cage chaetae as long as 1/6 body length, or slightly longer than body width. Chaetiger 1 involved in cephalic cage; chaetae arranged in short dorsoventral series; 4–5 notochaetae and 2–3 neurochaetae per fascicle; first neuropodia swollen, rounded.

Anterior dorsal margin of first chaetiger papillated, not projected anteriorly. Chaetigers 1–3 of similar length. Chaetal transition from cephalic cage to body chaetae abrupt; large aristate neurospines present from chaetiger 2. Ventral gonopodial lobes not seen ( Fig. 37C ).

Parapodia poorly developed, chaetae emerge from body wall ( Fig. 37D ). Parapodia lateral; median neuropodia ventrolateral. Notopodia and neuropodia close to each other; short low conical lobes, neuropodial ones larger.

Median notochaetae in tufts, one per fascicle, all multiarticulate capillaries, articles very long ( Fig. 37E ); chaetae (chaetiger 6) about as long as ½ body width. Neurochaetae multiarticulate capillaries in chaetiger 1; aristate neurospines from chaetiger 2, very large in chaetigers 2–4, decrease in size posteriorly, 3-5 neurospines in anterior chaetigers ( Fig. 38F ), only 1–2 in posterior ones. Neurospines with very short anchylose articles basally and medially, distally hyaline, curved, aristate.

Posterior end tapered into truncate cone; pygidium with anus terminal, provided with a long anal tube; anal cirri absent.

Variation. Additional specimens 4.0– 6.8 mm long, 1.0– 1.8 mm wide, cephalic cage 0.5–1.3 mm long, 12–22 chaetigers.

Remarks. Bradabyssa kirkegaardi n. sp. closely resembles B. monnioti n. sp. because both have whitish bodies with fine sediment particles adhering to papillae, mainly basally. However, they differ because in B. kirkegaardi the body wall is homogeneous, smooth, without any transverse ridges, and notochaetae all have long articles, whereas in B. monnioti the body is rugose, with about three transverse ridges per segment, and notochaetae have short articles. The specimens were found in quite different depths (6730–6850 m vs 632–2408 m) and this unusual bathymetric pattern may involve more than a single species, but better preserved specimens are needed to resolve this.

Etymology. This species is named after the late Dr. J. B. Kirkegaard, a well known specialist in abyssal polychaetes, in recognition of his many studies on polychaetes, and especially because he noticed some unusual features in this specimen, which is now named after him.

Distribution. Sunda Trench, Eastern Tropical Indian Ocean, in over 6700 m, and from the Tasman Sea in 600–960 m depth.

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.

FIGURE 37. Bradabyssa kirkegaardi n. sp., holotype (ZMUC 1781). A. Dorsal view. B. Ventral view. C. Anterior region, ventral view. Non-type specimen (SMF Sonne 136): D. Anterior chaetiger, right parapodium, anterior view. E. Same, lower notochaetae, basal and medial regions. F. Same, neurochaetal basal, medial and distal regions. Scale bars. A: 0.7 mm, B: 0.8 mm, C: 0.4 mm, D: 0.1 mm, E: 15 µm, F: 30 µm.

FIGURE 38. Bradabyssa mezianei n. sp., holotype (MNHN IA-Type 1793). A. Dorsal view. B. Ventral view. Paratype (MNHN IA-Type 1794): C. Midbody chaetiger, right parapodium, anterior view. D. Same, basal, medial and distal notochaetal regions. E. Same, basal, medial and distal neurochaetal regions. Scale bars. A – B: 0.4 mm, C: 0.2 mm, D – E: 20 µm.