Bathyfauvelia glacigena, 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 : 585-589

BATHYFAUVELIA GLACIGENA SP. NOV.

( FIG. 8A–L; TABLES 1–3)

Polychaeta sp. EBS26o-Po92 (GenBank KJ736543) Janssen et al. (2015);

Polychaeta sp. EBS47o-Po66 (GenBank KJ736542) Janssen et al. (2015);

Polychaeta sp. NB-Po145 (GenBank KJ736541) Janssen et al. (2015).

Type material: Holotype, MNHN-IA-TYPE 1817 ( IFR521-1 ), complete, length 5.43 mm, width 0.91 mm, 18 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 1, MNHN-IA-TYPE 1818 ( IFR302 ), complete, length 3.31 mm, width 0.61 mm, 16 segments (including tentacular segment), Equatorial Eastern Pacific Ocean , Clarion-Clipperton Fracture Zone, IOM license area, station 99, collected 4 April 2015, epibenthic sledge supra-net, start 11°2.296′N, 119°40.825′W, end 11°2.612′N, 119°39.512′W, 4398–4402 m depth, 2529 m trawling distance . Paratype 2, NHMUK 2018.25347 ( IFR529-2 - 1 ) , complete, length 2.70 mm, width 0.56 mm, 15 segments (including tentacular segment), Equatorial Eastern Pacific Ocean , Clarion- Clipperton Fracture Zone , GSR license area, station 117, collected 7 April 2015, epibenthic sledge epi-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 .

Additional material: Specimen 1, MNHN-IA-PNT 74 ( IFR520-7 ), incomplete, length 1.38 mm, width 0.30 mm, nine segments (including tentacular segment), Equatorial Eastern Pacific Ocean , Clarion- Clipperton Fracture Zone , GSR license area, station 117, collected 7 April 2015, epibenthic sledge supranet, 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. Specimen 2, MNHN-IA-PNT 75 ( IFR529-2 - 2 ), incomplete, length 1.13 mm, width 0.26 mm, eight segments (including tentacular segment), Equatorial Eastern Pacific Ocean, Clarion-Clipperton Fracture Zone, GSR license area, station 117, collected 7 April 2015, epibenthic sledge epi-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. Specimen 3, P.B. ’s collection ( IFR636-5 - 4 ), incomplete, length 1.10 mm, width 0.30 mm, eight segments (including tentacular segment), Equatorial Eastern Pacific Ocean, Clarion-Clipperton Fracture Zone, Ifremer license area, station 158, collected 15 April 2015, epibenthic sledge epi-net, start 14°3.411′N, 130°7.989′W, end 14°3.813′N, 130°6.481′W, 4946–4978 m depth, 3789 m trawling distance .

Description(basedonholotypeandparatypes): Holotype complete, 5.43 mm long and 0.91 mm wide for 18 segments (including tentacular segment), slightly dorsoventrally flattened, slightly tapering posteriorly; live specimen bluish, slightly translucent ( Fig. 8A); ethanol-preserved specimen pale white, prostomium transparent with two large white patches interiorly.

Prostomium bilobed, wider than long, lobes not so pronounced, anteriorly tapering to short pointed cephalic peaks ( Fig. 8B); 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 in holotype; in paratype (MNHN-IA-TYPE 1818) style papillated ( Fig. 8L), tapering into thin tips, short (reaching to segment 4). Palps smooth, tapering, short (reaching to segment 5–6; Fig. 8B). 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 ( Fig. 8B); styles missing in holotype; in paratype (MNHN-IA-TYPE 1818) dorsal tentacular style papillated, tapering into thin tips, long (reaching to segment 2), ventral tentacular cirri missing. Pharynx not everted in holotype; dissected in paratype (NHMUK 2018.25347), with nine pairs of distal equal-sized, subtriangular papillae; two pairs of jaws, each with main fang, outer margin with few (four to six) smaller teeth ( Fig. 8E). 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 (all elytra missing in holotype); in paratype (MNHN-IA-TYPE 1818), elytra still attached on segments 2 and 7, large, covering dorsum and parapodia, the largest overlapping about six segments, milky, translucent, kidney-shaped ( Fig. 8C); almost entire margin papillated, except on anterior and inner parts, papillae smooth, thin, short to long, rather well spaced ( Fig. 8D); surface densely and uniformly covered by microtubercles, except for overlapping parts; microtubercles rounded, covered by one to numerous button-like papillae, some microtubercles with distal long papillae, uniformly present on surface ( Fig. 8D).

Cirrigerous segments with distinct, cylindrical dorsal cirrophores ( Fig. 8F), inserted subdistally on notopodia; styles missing in holotype; in paratype (MNHN-IA-TYPE 1818) style papillated, tapering into thin tips, long (much longer than tip of neuroacicular lobe); dorsal tubercles forming lamelliform branchiallike processes ( Fig. 8F), small on segment 3, becoming longer from segment 6–8 (shorter, smaller than elytrophores).

Ventral cirri smooth, tapering into thin tips, present from segment 2 to last segment; inserted basally on neuropodia of segment 2, style missing on holotype, in paratype (MNHN-IA-TYPE 1818) long (slightly longer than tip of neuroacicular lobe); in subsequent segments ( Fig. 8F) inserted medially on neuropodia of mid-body and basally on neuropodia of anteroposterior body, styles very short (shorter than tip of neuroacicular lobe); last ventral cirri about as long as neuropodial lobe of same segment.

Parapodia subbiramous; notopodia shorter than neuropodia ( Fig. 8F). 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 (five or six observed), short to long, stout, slightly curved with distinct spinous rows on convex side, with blunt tips ( Fig. 8G); and (2) moderate in number (five to 13 observed), long to very long, slender, slightly curved with distinct, well-developed spinous rows, with blunt tips ( Fig. 8H); notochaetae stouter than neurochaetae. Neurochaetae of two types: (1) upper group, few (five observed), long to very long, distally flattened to concave, serrated along both margins, with pointed tips ( Fig. 8I); and (2) middle and lower group, moderate in number (20 observed), long to short, stouter, distally concave to folded, with spines (three to 19 observed) along both margins, with gently curved pointed tips ( Fig. 8J); the lower neurochaetae in fascicle much shorter, with fewer lateral spines (about three observed; Fig. 8K), not present on segments 2–4; in last segment, neurochaetae can be very thin.

Nephridial papillae present on segments 12 and 13, globular. Pygidium rounded, enclosed by last segment; with dorsal anus ( Fig. 8A). Anal cirri lost, scars not seen.

Morphological variation: Only one specimen shows an adult size, confirmed by the presence of nephridial papillae. All the other specimens appear to be juveniles sharing many similarities with the adult: long palps (reaching to segment 4–5) and form of notochaetae and neurochaetae. However, the prostomium in juveniles shows a wider notch, and peaks are poorly developed.

Remarks: Currently, only two species belonging to Bathyfauvelia are valid: Bathyfauvelia affinis and Bathyfauvelia grandelytris ( Levenstein, 1975) . Both species share the presence of pointed cephalic peaks (anterior end), presence of cirriform dorsal tubercle and only one type of neurochaetae, whereas the new species described here presents a similar prostomium shape and dorsal tubercle but has two types of neurochaeta present ( Table 3). Bathyfauvelia glacigena sp. nov. is very similar to Bathyfauvelia ignigena sp. nov., and the two species can be easily confused ( Table 3), but evidence from DNA shows that they are distinct species ( Fig. 2). This was confirmed by the average K2P distance between them (14.0% for COI and 7.8% for 16S). Adult specimens of Bathyfauvelia glacigena sp. nov. have 18 segments, prostomial lobes anteriorly tapering to pointed cephalic peaks, palps slightly longer (reaching to segment 5–6) and the last ventral cirri about as long as the neuropodial lobe. In contrast, Bathyfauvelia ignigena sp. nov. has 19 segments, prostomial lobes anteriorly tapering to rounded cephalic peaks, palps slightly shorter (reaching to segment 3–4) and the last ventral cirri slightly longer than the neuropodial lobe. Only one adult specimen of Bathyfauvelia glacigena sp. nov. with 18 segments has been observed, and it is unclear whether this is the maximal number of segments for the species. More specimens are needed to confirm this character. It should be noted that prostomial lobes anteriorly tapering to blunt cephalic peaks were also observed in a few juvenile specimens of Bathyfauvelia glacigena sp. nov., suggesting that this character is ontogenetic and should be used only to differentiate adult specimens. The length of palps and ventral cirri on the last segment appear to be more consistent characters for separating these two species. Both species have overlapping distributions in the IOM and GSR license areas. In addition, Bathyfauvelia glacigena sp. nov. was also sampled in the Ifremer license area, and Bathyfauvelia ignigena sp. nov. was also sampled in APEI#3.

Etymology: The species name glacigena means ‘iceborn’, which is composed by borrowing from the Latin word ‘ glăc ĭ ēs ’ meaning ‘ice’ and the Greek word ‘gennó, γεννώ’ meaning ‘born’. It refers to white ganglia like ice.

Genetic data: DNA sequencing for this species was successful for COI, 16S and 18S, respectively sharing at least 98.6, 99.5 and 100% of genetic material between the specimens. The average K2P distance for intraspecific variation was 1.6% for COI and 0.2% for 16S.

Distribution: Based on the material examined (six specimens), this species has a wide distribution within the Clarion-Clipperton Fracture Zone, being sampled in the IOM, GSR (type locality) and Ifremer license areas.

References for species are provided in Table 2. ‘?’ indicates uncertain information.