Bathyfauvelia ignigena, Bonifácio & Menot, 2019

Bonifácio, Paulo & Menot, Lénaïck, 2019, New genera and species from the Equatorial Pacific provide phylogenetic insights into deep-sea Polynoidae (Annelida), Zoological Journal of the Linnean Society 185, pp. 555-635 : 589-591

BATHYFAUVELIA IGNIGENA SP. NOV.

( FIG. 9A–R; TABLES 1–3)

Polychaeta sp. NB-Po595 (GenBank KJ736540) Janssen et al. (2015).

Type material: Holotype, MNHN-IA-TYPE 1819 ( IFR674-2 ), complete, length 5.65 mm, width 0.80 mm, 19 segments (including tentacular segment), Equatorial Eastern Pacific Ocean , Clarion-Clipperton Fracture Zone, IOM license area, station 81, collected 1 April 2015, epibenthic sledge supra-net, start 11°3.900′N, 119°37.812′W, end 11°4.171′N, 119°36.661′W, 4365– 4346 m depth, 2739 m trawling distance . Paratype 1, MNHN-IA-TYPE 1820 ( IFR521-3 ), complete, length 5.80 mm, width 1.08 mm, 19 segments (including tentacular segment), Equatorial Eastern Pacific Ocean , Clarion-Clipperton Fracture Zone, GSR license area, station 117, collected 7 April 2015, epibenthic sledge supra-net, start 13°52.317′N, 123°15.442′W, end 13°52.622′N, 123°14.263′W, 4498–4521 m depth, 3129 m trawling distance . Paratype 2, NHMUK 2018.25348 ( IFR655-1 - 1 ) for SEM, complete, length 5.67 mm, width 0.91 mm, 19 segments (including tentacular segment), Equatorial Eastern Pacific Ocean , Clarion-Clipperton Fracture Zone , APEI#3 , station 192, collected 21 April 2015, epibenthic sledge epi-net, start 18°44.807′N, 128°21.874′W, end 18°45.338′N, 128°20.418′W, 4821– 4820 m depth, 2799 m trawling distance.

Additional material: Specimen 1, MNHN-IA-PNT 76 ( IFR665 ), incomplete, length 4.89 mm, width 0.0. 88 mm, 13 segments (including tentacular segment), Equatorial Eastern Pacific Ocean , Clarion- Clipperton Fracture Zone, APEI#3 , station 197, collected 22 April 2015, epibenthic sledge epi-net, start 18°48.659′N, 128°22.753′W, end 18°49.088′N, 128°21.289′W, 4805–4823 m depth, 2529 m trawling distance. Specimen 2, P.B. ’s collection ( IFR694 ), complete juvenile specimen, length 1.27 mm, width 0.28 mm, 12 segments (including tentacular segment), Equatorial Eastern Pacific Ocean, Clarion-Clipperton Fracture Zone, APEI#3 , station 197, collected 22 April 2015, epibenthic sledge epi-net, start 18°48.659′N, 128°22.753′W, end 18°49.088′N, 128°21.289′W, 4805– 4823 m depth, 2529 m trawling distance .

Description(basedonholotypeandparatypes): Holotype complete, 5.65 mm long and 0.80 mm wide for 19 segments (including tentacular segment), dorsoventrally flattened, slightly tapering posteriorly; colour of live animal not known; ethanol-preserved specimen pale white, prostomium transparent with two large white patches interiorly ( Fig. 9A).

Prostomium bilobed, wider than long, lobes not so pronounced, anteriorly tapering to short rounded cephalic peaks ( Fig. 9B, H); frontal filaments absent; median notch between prostomial lobes wide and moderately deep; eyes absent; a pair of internal white ganglia visible through translucent epidermis. Median antenna present, lateral antennae absent; ceratophore of median antenna bulbous, small, short (shorter than anterior margin of prostomial lobes), inserted medially on prostomium, near median notch; style missing. Palps smooth, distally tapering abruptly, short (reaching around segment 4; Fig. 9H). Facial tubercle absent. Upper lip with few folds.

Tentacular segment with elongate acicular lobe, inserted laterally and slightly ventral to prostomium; with acicula not penetrating epidermis, with chaetae; tentaculophores distinct, small, equal sized, inserted subdistally; dorsal tentacular style missing; ventral tentacular style papillated, tapering into thin tip, long (reaching segment 5), thin ( Fig. 9H). Pharynx not everted on holotype; dissected in paratype (NHMUK 2018.25348), with nine pairs of distal equal-sized, subtriangular papillae; two pairs of jaws, each with main fang, margin serrated with few (four or five) smaller teeth ( Fig. 9K). Second segment with elytrophores, subbiramous parapodia, chaetae and ventral cirri.

Nine pairs of massive, large elytrophores present on segments 2, 4, 5, 7, 9, 11, 13, 15 and 17 (on holotype elytra present on segments 2 and 4); eytra large (covering dorsum and parapodia, the largest overlapping about four to five segments), milky, translucent, kidney shaped ( Fig. 9I); almost entire margin papillated, except on anterior and inner parts, papillae smooth, thin, long, rather well spaced ( Fig. 9J); surface densely and uniformly covered by microtubercles, except overlapping parts; microtubercles rounded, few covered distally with one to few button-like papillae, few papillae present on surface ( Fig. 9J).

Cirrigerous segments with distinct, cylindrical dorsal cirrophores ( Fig. 9L), inserted subdistally on notopodia; styles missing; dorsal tubercles forming lamelliform branchial-like processes ( Fig. 9C, L), small on segment 3, becoming longer from segment 6 (approaching cirrophore; Fig. 9C).

Ventral cirri smooth, tapering, present from segment 2 to last segment; inserted basally on neuropodia of segment 2, style long (longer than tip of neuroacicular lobe); in subsequent segments inserted medially on neuropodia but basally on neuropodia of posterior segments ( Fig. 9L), styles very short (shorter than tip of neuroacicular lobe); last ventral cirri longer than neuropodial lobe of same segment.

Parapodia subbiramous; notopodia shorter than neuropodia ( Fig. 9L). Notopodia subtriangular, tapering into long acicular lobe, tip of notoacicula not penetrating epidermis. Neuropodia large, subtriangular, tapering into long acicular lobe, tip of neuroacicula not penetrating epidermis. Notochaetae of two types: (1) few (six to eight observed), short to long, stout, slightly curved with distinct spinous rows on curved side, with blunt tips ( Fig. 9D, M); and (2) moderate in number (13 observed), long to very long, slender, slightly curved with distinct, well-developed spinous rows, with blunt tips ( Fig. 9E, N); notochaetae stouter than neurochaetae. Neurochaetae of two types: (1) upper group, moderate in number (~12 observed), long to very long, distally flattened to concave, serrated along both margins, with pointed tips ( Fig. 9F, O); and (2) middle and lower group, moderate in number (25 observed), long to short, stouter, distally concave to folded, with spines (two to 19 observed) along both margins, with gently curved pointed tips ( Fig. 9G, P–R); the lower neurochaetae in fascicle much shorter ( Fig. 9Q, R), with fewer lateral spines (two or three observed), not present on segments 2–4; in last segment neurochaetae can be very thin.

Nephridial papillae on segments 12 and 13, globular. Pygidium rounded, slightly enclosed by last segment; with dorsal anus ( Fig. 9A). Anal cirri lost, scars not seen.

Morphological variation: Most of the specimens have an adult size with 19 segments, with few morphological variations. Only one adult specimen presents a very short palp (MNHN-IA-PNT 76, reaching segment 2), which might be regenerating. The only juvenile specimen, with 12 segments, already has the two types of both notochaetae and neurochaetae present in adults but less numerous. However, the prostomial lobes (slightly wider), the prostomial peaks (poorly developed) and the dorsal tubercles (poorly developed) differ from the adults.

Remarks: Bathyfauvelia ignigena sp. nov. differs from Bathyfauvelia glacigena sp. nov. in having 19 segments, rounded cephalic peaks, slightly shorter palps (reaching to segment 3–4) and slightly longer ventral cirri than neuropodial lobes on the last parapodia. See Remarks on Bathyfauvelia glacigena sp. nov. and Table 3 for more details.

Etymology: Species named from the ‘ ignĭgĕna ’, a poetical epithet of Bacchus meaning ‘fire-born’, which is composed by borrowing from the Latin word ‘ ignis ’ meaning ‘fire’ and the Greek word ‘gennó, γεννώ’ meaning ‘born’.

Genetic data: DNA sequencing for this species was successful for COI, 16S and 18S (only one specimen). The specimens shared ≥ 99.3% for COI and 100% and for 16S. The average K2P distance for intraspecific variation was 0.4% for COI and 0.0% for 16S.

Distribution: Based on the material examined (five specimens), this species has a wide distribution within the Clarion-Clipperton Fracture Zone, being sampled in IOM (type locality), GSR, Ifremer ( Janssen et al., 2015) and APEI#3 areas.