Bradabyssa abyssalis ( Fauchald, 1972 ) 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 : 40-41

Bradabyssa abyssalis ( Fauchald, 1972) n. comb.

Figure 19

Pherusa abyssalis Fauchald, 1972: 226 –228, Pl. 47, figs a–e.

Type material. Eastern Tropical Pacific. Holotype ( LACM 1028 ) and paratype ( LACM 1029 ) of Pherusa abyssalis , 30 km off Isla Cerralvo , Gulf of California, Mexico, R.V. Velero IV, Sta. 11776 (24°41'30" N, 109°56'20" W), 1089 m, 18 Nov. 1967 (paratype a median and a posterior fragment, probably from the same specimen than holotype) .

Additional material. Eastern Tropical Pacific. Two specimens ( UNAM 7897 ), R.V. El Puma, Cruise Talud VI, Sta. 18 (24°15' N, 108°16' W), modified Darling dredge, 920 m, 15 Mar. 2001 (19.0– 22.5 mm long, 2.0– 2.3 mm wide, cephalic cage 3 mm long, 35–43 chaetigers; gonopodial lobes in chaetiger 5).

Description. Holotype (LACM 1028) an anterior fragment, pale, damaged, anterior end exposed, several parapodia removed ( Fig. 19A ); 17 mm long, 2.5 mm wide, cephalic cage 4 mm long, 24 chaetigers. Tunic with fine sediment particles; body papillae rounded in two different sizes, in 5–6 transverse series, larger dorsally.

Anterior end exposed, markedly eroded. Prostomium small lobe. Caruncle well preserved, separating branchial plate, median keel and lateral ridges converging posteriorly ( Fig. 19C ). Palps missing, size relative to branchiae unknown.

Most branchiae missing, branchial scars on a branchial plate, arranged in two lateral groups, each with filaments in radiating series, about 100 scars per group. Lips distinct; upper lip rounded, small; lateral lips with an anterior projection. Ventral lip reduced; ventral pharyngeal organ partially exposed, with two rounded lateral lobes. Nephridial lobes not seen.

Cephalic cage chaetae about twice as long as body width. Chaetigers 1 and 2 larger, with longer chaetae than following chaetigers, 3–4 notochaetae, 2–3 neurochaetae per ramus ( Fig. 19B ). Following chaetigers with smaller notochaetae.

Anterior dorsal margin of first chaetiger rounded, smooth (papillae probably eroded). Anterior chaetigers without especially long papillae. Chaetigers 1–3 of similar length but chaetal lobes larger in chaetigers 1–2. Chaetal transition from cephalic cage to body chaetae abrupt; aristate neurospines present from chaetiger 2. Gonopodial lobes short, pale, digitate in chaetiger 5 ( Fig. 19C ).

Parapodia well developed, lateral ( Fig. 19D ). Median neuropodia ventrolateral. Notopodia and neuropodia close to each other. Notopodia short low rounded lobes, with 1–2 long papillae. Neuropodia larger rounded lobe, 4–6 marginal papillae (mostly eroded), each digitate, 2 prechaetal and 3–4 postchaetal papillae.

Median notochaetae arranged in short transverse series; all notochaetae multiarticulate capillaries, short articles basally, medium-sized medially, long distally; 6–8 per bundle, twice as long as body width. Chaetiger 1 neurochaetae multiarticulate, aristate neurospines from chaetiger 2, bent, with a median notch ( Fig. 19E ); 5–6 per bundle, arranged in È-shaped patterns; each neurospine with rings short, decreasing medially, not continued beyond median notch, tip hyaline, recurved.

Posterior end unknown; paratype with posterior region tapered into rounded lobe; pygidium with anus dorsoterminal, opening round; anal cirri absent.

Variation. Complete specimens 19.0– 22.5 mm long, 2.0– 2.3 mm wide, cephalic cage 3 mm long, 35–43 chaetigers; gonopodial lobes in chaetiger 5.

Remarks. Bradabyssa abyssalis ( Fauchald, 1972) n. comb. resembles B. irenaia ( Chamberlin, 1919) n. comb. by having about 5 transverse series of dorsal tubercles per segment. They differ because in B. abyssalis the integument is pale and neurochaetae are medially cleft, whereas in B. irenaia the integument is dark and neurochaetae are tapered. Furthermore, in B. abyssalis notochaetae have short articles basally only, whereas they are present basally and also medially in B. irenaia .

Distribution. Gulf of California, in 920–1089 m water depth.

Figures

FIGURE 19. Bradabyssa abyssalis (Fauchald, 1972) n. comb., holotype (LACM 1028). A. Oblique, right lateral view. B. Anterior end, left lateral view. C. Anterior end, ventral view (arrow points to left gonopodial lobe; Br: branchial scars). D. Chaetiger 17, right parapodium, posterior view. E. Same, neurochaetae (insets: medial regions with transverse notch). Scale bars: A: 1.3 mm, B, C: 0.8 mm, D: 170 µm, E: 130 µm.