Macellicephaloides moustachu, 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 : 608-611

MACELLICEPHALOIDES MOUSTACHU SP. NOV.

( FIG. 16A–J; TABLES 1, 2)

Type material: Holotype, MNHN-IA-TYPE 1832 ( IFR421 ), complete, length 2.69 mm, width 0.66 mm, 15 segments (including tentacular segment), Equatorial Eastern Pacific Ocean , Clarion-Clipperton Fracture Zone, IOM license area, station 99, collected 4 April 2015, epibenthic sledge epi-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 1, MNHN-IA-TYPE 1833 ( IFR520-1 ), complete, length 1.97 mm, width 0.52 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 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, MNHN-IA- TYPE 1834 ( IFR449 b), complete, length 1.41 mm, width 0.46 mm, 15 segments (including tentacular segment), Equatorial Eastern Pacific Ocean , Clarion- Clipperton Fracture Zone , Ifremer license area, station 158, collected 15 April 2015, epibenthic sledge supra-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. Paratype′ 3, MNHN-IA-TYPE 1835 ( IFR529-1 ), incomplete for SEM, length 1.24 mm, width 0.40 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 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 . Paratype 4, NHMUK 2018.25351 ( IFR208 ) , complete, length 2.19 mm, width 0.52 mm, 15 segments (including tentacular segment), Equatorial Eastern Pacific Ocean , Clarion-Clipperton Fracture Zone , BGR license area, station 20, collected 21 March 2015, epibenthic sledge epi-net, start 11°50.15′N, 117°58.49′W, end 11°50.18′N, 116°58.46′W, 4144– 4093 m depth, 2769 m trawling distance . Paratype 5, NHMUK 2018.25352 ( IFR538-3 ) , complete, length 2.13 mm, width 0.51 mm, 14 segments (including tentacular segment), Equatorial Eastern Pacific Ocean , Clarion-Clipperton Fracture Zone , GSR license area, station 133, collected 10 April 2015, epibenthic sledge supra-net, start 13°50.751′N, 123°15.649′W, end 13°51.126′N, 123°14.131′W, 4516– 4427 m depth, 2289 m trawling distance .

Additional material: Specimen 1, MNHN-IA- PNT 79 ( IFR422 ), complete, length 2.75 mm, width 0.62 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 epi-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. Specimen 2, MNHN-IA-PNT 80 ( IFR423 ), complete, length 1.84 mm, width 0.44 mm, 15 segments (including tentacular segment), Equatorial Eastern Pacific Ocean , Clarion-Clipperton Fracture Zone, IOM license area, station 99, collected 4 April 2015, epibenthic sledge epi-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. Specimen 3, MNHN-IA-PNT 81 ( IFR682 ), complete, length 1.11 mm, width 0.30 mm, 11 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. Specimen 4, P.B. ’s collection ( IFR460 b), incomplete, length 1.40 mm, width 0.42 mm, ten 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, 2.69 mm long and 0.66 mm wide for 15 segments (including tentacular segment), slightly dorsoventrally flattened, slightly tapering posteriorly; live specimen bluish; ethanol-preserved pale brown ( Fig. 16A), with brownish bands subbasally on palps and medially on dorsal cirri; prostomium whitish.

Prostomium bilobed but continuously fused, wider than long, lobes not pronounced anteriorly but extending to ventral side ( Fig. 16A–D); frontal filaments small, inserted anteriorly ( Fig. 16A–C); median notch between prostomial lobes absent; eyes absent. Median antenna present, lateral antennae absent; ceratophore of median antenna cylindrical, short (shorter than distance between ceratophore insertion and posterior margin of prostomium), inserted anteriormedially on prostomium; style missing in holotype; in paratype (MNHN-IA-TYPE 1833) style smooth, tapering into thin tips, long (reaching segment 5). Palps smooth, tapering, long (reaching segment 4–5), inserted ventrally, directed ventroposteriorly ( Fig. 16C, D). Pharynx not everted in holotype; dissected in paratype (MNHN-IA-TYPE 1834), with pharyngeal papillae not possible to count; two pairs of jaws, dorsal jaw fused, each dorsal jaw with two main blunt teeth, innermost one with a smaller, pointed secondary tooth, margin smooth ( Fig. 16E); each ventral jaw with one main blunt tooth, outer margin serrated (four to five small teeth), with two smaller secondary teeth, pointed on each side, margin smooth and short ( Fig. 16F). Bilobed facial tubercle, very small, located between palps and upper lip ( Fig. 16D). In most specimens, bilobed facial tubercle difficult to see but made visible using forceps to move palps apart.

Tentacular segment very reduced, fused to prostomium, with very short lobe, inserted ventrolaterally to prostomium;withoutaciculaorchaetae;tentaculophores small but distinct, dorsal tentaculophores slightly smaller than ventral tentaculophores; styles missing in holotype; in paratype (MNHN-IA-TYPE 1833), styles smooth, tapering into thin tips, short; dorsal tentacular style shorter than ventral tentacular style (reaching segment 4). Second segment with elytrophores, subbiramous parapodia, with chaetae and ventral cirri. Segments 3 and 4 medioventrally inflated, forming a truncated structure ( Fig. 16C).

Eight pairs of knob-like elytrophores present on segments 2, 4, 5, 7, 9, 11, 13 and 15 (all elytra missing); on segment 2, elytrophores larger.

Cirrigerous segments with large, cylindrical, elongate dorsal cirrophores ( Fig. 16G); dorsodistal, pointed projection ( Fig. 16G) on cirrophores; styles smooth, tapering into long thin tips, long (much longer than tip of neuroacicular lobe), mostly directed posteriorly; dorsal tubercle absent.

Ventral cirri smooth, tapering, present from segment 2 to last segment; inserted basally on neuropodia of segment 2, style missing in holotype; in paratypes (MNHN-IA-TYPE 1833 and MNHN-IA-TYPE 1835), style short (shorter than tip of neuroacicular lobe); in subsequent segments inserted distally on neuropodia, styles short on segments 3 and 4 (shorter than tip of neuroacicular lobe) and long from segment 5 (longer than tip of neuroacicular lobe).

Parapodia subbiramous, notopodia very reduced, much shorter than neuropodia( Fig.16G).Notopodia with inconspicuous to very short acicular lobe, notoacicula slender, tip of notoacicula not penetrating epidermis. Neuropodia large, subtriangular, tapering into long acicular lobe, tip of neuroacicula not penetrating epidermis. Notochaetae absent. Neurochaetae moderate in number (nine to 22 observed), short to long, very narrow, distally with spines along both margins, with pointed tips ( Fig. 16H–J).

Nephridial papillae present on segments 7–14, small, bulbous. Pygidium rounded, with minute papilla ventrally; slightly enclosed by last segment; with terminal anus ( Fig. 16A). Anal cirri lost, scars not seen.

Morphological variation: The specimens vary in the number of segments from 11 (MNHN-IA-PNT 81) to 16 (MNHN-IA-PNT 79) but share many of the morphological characters described above except for the number of pairs of elytra and the presence of nephridial papillae. The specimen with 11 segments presents five pairs of elytrophores and no nephridial papillae; these characters are probably linked to growth.

Methyl Green staining pattern: The paratype (NHMUK 2018.25351) stains slightly but uniformly all along the body (not shown). Two densely stained spots are observed anteriorly on prostomium, located close to the median ceratophore.

Remarks: Among the eight species described in Macellicephaloides only one species, Macellicephaloides improvisa Levenstein, 1983 , shows notopodia shorter than neuropodia, with thin notoacicula ( Pettibone, 1989b). However, the new species Macellicephaloides moustachu sp. nov. differs from Macellicephaloides improvisa in having up to 16 segments and elongate cirrophores with a distal pointed projection, whereas Macellicephaloides improvisa has 18 segments and short cirrophores without a distal pointed projection. Macellicephaloides moustachu sp. nov. is a relatively common species in the CCFZ, with> 38 specimens sampled in four out of the five areas. Unfortunately, only the 18S gene could be sequenced; DNA amplification of the 16S and COI genes was unsuccessful. Consequently, identification of damaged specimens was challenging.

Etymology: The species name came from the French word ‘ moustachu ’ meaning ‘with a moustache’. It refers to the palps directed ventrally, giving the impression that the worm has a moustache.

Genetic data: DNA sequencing for this species was successful only for 18S but not for COI or 16S, sharing 100% of genetic material between the specimens.

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

Reproductive notes: Paratype MNHN-IA-TYPE 1833 seems to be brooding dorsally; two large interconnected pouches were observed linked to the body through an anterior small hole on the notopodia of segment 10. The sac directly connected to the body is surrounded by a membrane and has visible small ova inside; the second sac shows an agglomerate of small ova without a visible membrane.