Bradabyssa mezianei, 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 : 74-76

Bradabyssa mezianei n. sp.

Figure 38

Ilyphagus cf ilyvestis: Amoureux 1982: 191 , Fig. 2I .

Type material. Northeastern Atlantic Ocean. Holotype ( MNHN IA-Type 1793), R.V. Thalassa, Cruise 1973, Sta. 410 (47°50'07" N, 08°09'03" W) , 1180 m, sand and rocks, Oct. 1973. Two paratypes ( MNHN IA-Type 1794), one anterior and one median fragment, R.V. Thalassa, Cruise 1973, Sta. 410 (47°50'07" N, 08°09'03" W) , 1180 m, sand and rocks, Oct. 1973 (anterior fragment severely eroded dorsally, 3.8 mm long, 1.5 mm wide, cephalic cage 0.4 mm long, 11 chaetigers). Four paratypes ( MNHN IA- Type 1795), three anterior and one posterior fragments, R.V. Thalassa, Cruise 1973, Sta. 447 (48°47'03" N, 11°12'00" W → 48°47'04" N, 11°14'03" W) , 1430–1550 m, soft bottom, Oct. 1973 (2.3–3.5 mm long, 0.8–1.5 mm wide, cephalic cage 0.5–0.8 mm long, 8–11 chaetigers; chaetiger 7 with 3–4 notochaetae, 3 neurochaetae; one with most papillae eroded). Two paratypes ( MNHN IA-Type 1796), median and posterior fragments, R.V. Thalassa, Cruise 1973, Sta. 454 (48°37'01" N, 10°53'04" W → 48°39'00" N, 10°55'00" W) , 1700–1810 m, soft bottom with stones, Oct. 1973.

Additional material. Several fragments ( MNHN IA-PNT 39 ), four anterior ones; all with papillae completely eroded, R.V. Thalassa, Cruise 1973, Sta. 410 (47°50'07" N, 08°09'03" W), 1180 m, mud and rocks, Oct. 1973 . Four specimens ( MNHN IA-PNT 40 ), two anterior and two median fragments, R.V. Thalassa, Cruise 1973, Sta. 429 (48 28'00" N, 0 9 50'00" W), 1300 m, mud and calcareous rocks, Oct. 1973 . Three specimens ( MNHN IA-PNT 41 ), two anterior and one posterior fragments, R.V. Thalassa, Cruise 1973, Sta. 438 (48°33'07" N, 10°25'00" W), 1400 m, mud and compacted particles, Oct. 1973 . Two specimens ( MNHN IA-PNT 42 ), two median fragments, damaged, R.V. Thalassa, Cruise 1973, Sta. 447 (47°47'03" N, 11°12'00" W → 48°47'04" N, 11°14'03" W), 1200–1520 m, mud, Oct. 1973 . Five specimens ( MNHN IA-PNT 43 ), two anterior and three median fragments, R.V. Thalassa, Cruise 1973, Sta. 459 (48°37'03" N, 09°53'00" W), 1180 m, sandy mud with compact pieces, Oct. 1973 (anterior fragment dissected for anterior end details). One specimen ( MNHN IA-PNT 44 ), a median fragment, R.V. Thalassa, Cruise 1973, Sta. 451 (48°39'03" N, 10°36'05" W), 1400 m, fine sand with compact pieces, Oct. 1973 .

Description. Holotype (MNHN IA-Type 1793) an anterior fragment, yellowish, variously eroded; anterior end rounded, posteriorly incomplete ( Fig. 38A ). Body ovoid, with parallel sides; 3.5 mm long, 1.8 mm wide, cephalic cage 0.5 mm long, 10 chaetigers. Tunic densely papillated; papillae cirriform, basally swollen, tips rounded, slightly capitate, forming fusiform sediment tubercles, arranged in 10–12 transverse series of alternating papillae of similar size per segment, with sediment especially abundant medially; dorsal papillae as long as notochaetae, ventral ones slightly smaller ( Fig. 38B ).

Anterior end not exposed; details based on dissected additional specimens (MNHN IA-PNT 43). Prostomium low cone, pale. Eyes not seen (in non-type specimen, Sta. 429, frontal eyes black, posterior eyes not seen). Caruncle poorly developed, median keel and lateral ridges indistinct, continuing posteriorly, apparently reaching branchial plate posterior margin. Palps thick, about as long as branchiae, three times wider and slightly paler than branchiae; palp lobes rounded, low. Lateral lips well developed; ventral and dorsal lips reduced.

Branchiae cirriform, sessile on branchial plate, arranged as a discontinuous marginal row with four filaments per side; all filaments of similar size. Nephridial lobes in branchial plate not seen.

Cephalic cage chaetae as long as ¼ body width. Chaetiger 1 involved in cephalic cage, 2 notochaetae and 2 neurochaetae per side.

Anterior dorsal margin of first chaetiger papillate; papillae resembling those present dorsally. Chaetigers 1–3 becoming progressively longer. Chaetal transition from cephalic cage to body chaetae abrupt; aristate neurospines present from chaetiger 2. Gonopodial lobes not seen in holotype; some paratypes missing papillae have gonopodial lobes in chaetiger 5, lobes slightly wider than any nearby papillar base digitate, darker than surrounding body wall.

Parapodia poorly developed, lateral, covered by papillae ( Fig. 38C ). Median neuropodia ventrolateral. Notopodia and neuropodia close to each other.

Median notochaetae arranged in short transverse series, 5–6 per bundle (3–4 in smaller specimens), as long as 1/3 body width (some with notochaetae as long as body width), with medium-sized articles basally, alternating 2–3 short with 1 long article medially, becoming 3–4 short with 1 long distally ( Fig. 38D ). Neurochaetae multiarticulate capillaries in chaetiger 1; aristate neurospines present from chaetiger 2, arranged in oblique series, 4–6 per ramus; each aristate neurospine with slightly subdistal swell, with short rings basally, decreasing in size subdistally, tips hyaline, aristate ( Fig. 38E ).

Posterior end missing in holotype; one paratype (MNHN IA-Type 1796) with posterior end rounded, pygidium with anus ventro-terminal, anal cirri absent.

Remarks. Bradabyssa mezianei n. sp. closely resembles B. ilyvestis (Hartman, 1960) n. comb. as both species have very long papillae forming long, fusiform sediment tubercles. Study of the type material helped elucidate the enigmatic position of B. ilyvestis (see above). These two species differ in the relative number of chaetae and on the shape of neurochaetal tips: in B. mezianei there are 3–5 notochaetae per ramus and neurochaetal tips are slightly subdistally expanded, whereas in B. ilyvestis there are 8–9 notochaetae and neurochaetae are more expanded subdistally.

Etymology. This species is named after Tarik Meziane, curator of the Polychaete Collection in the Muséum National d’Histoire Naturelle, Paris, in recognition of his efforts for enhancing the study of this collection, and in recognition of his support for my research visits.

Distribution. Off Brest, France, in 1180–1810 m.

Figures

FIGURE 2. Brada granosa Stimpson, 1853. A. Neotype (USNM 1422407), lateral view, anterior end to the right (inset: small paratype, lower right in Fig. 3 A). B. Same, anterior end, ventral view (arrows point to gonopodial lobes). C. Non-type specimen (USNM 22851), head dissected, branchiae and palps removed (Br: branchial scar, PS: palp scar). Scale bars: A: 1.7 mm, B: 1.3 mm, C: 0.4 mm.

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.