Bathypolaria undetermined

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 : 592-593

BATHYPOLARIA SP. 173

( FIG. 10A, E; TABLES 1, 2)

Material examined: Specimen 1, MNHN-IA-PNT 63 ( IFR173 ), complete, length 3.45 mm, width 0.80 mm, probably 15 segments (including tentacular segment), Equatorial Eastern Pacific Ocean , Clarion-Clipperton Fracture Zone , BGR license area, station 20, collected 21 March2015,epibenthicsledgesupra-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. Specimen 2, MNHN- IA-PNT 64 ( IFR672 ), incomplete, length 1.80 mm, width 0.38 mm, nine 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. Specimen 3, MNHN- IA-PNT 65 ( IFR406 ), incomplete, length 3.54 mm, width 0.93 mm, 11 segments (including tentacular segment), originally complete with 15 segments, but the end was cut for molecular analysis; 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 .

Description (based on all specimens): Fragile worms, all damaged; parapodia, prostomial and parapodial appendages often missing. Body dorsoventrally cylindrical; live specimen with body surface translucent to milky, prostomium whitish, pharynx red; ethanol-preserved specimens with body surface pale white, prostomium white, pharynx internally red, longitudinal ventral whitish line ( Fig. 10A).

Prostomium bilobed, wider than long, lobes slightly pronounced, anteriorly rounded; frontal filaments absent; median notch between prostomial lobes moderately wide and deep ( Fig. 10A); eyes absent. Median antenna present, lateral antennae absent; ceratophore of median antenna small (not surpassing anterior end of prostomial lobes), inserted near median notch, style missing. Palps smooth, tapering, very long (reaching around segment 11). Facial tubercle bilobed.

Tentacular segment fused to prostomium, with a pair of short lobes, inserted laterally and slightly below prostomium; tentaculophores small; styles smooth, tapering; dorsal tentacular style very short (reaching segment 2); ventral tentacular style long (reaching around segment 4). Pharynx dissected, with seven pairs of distal subtriangular papillae; two pairs of jaws, each one with one main fang, outer margin with a secondary very small tooth (pointed or blunt). Lips of mouth in a bulbous projection when pharynx not everted.

Probably eight knob-like elytrophores present (all elytra missing).

Cirrigerous segments with distinct, cylindrical dorsal cirrophores; on segments 3 and 6 longer, anteriorly directed; styles missing; dorsal tubercles absent.

Ventral cirri smooth, tapering, present from segment 2 to last segment; inserted basally on neuropodia of segment 2, style short (much shorter than tip of neuroacicular lobe); missing in subsequent segments.

Parapodia subbiramous; notopodia shorter than neuropodia. Notopodia tapering into long acicular lobe, tip of notoacicula not penetrating epidermis. Neuropodia rectangular, tapering into long acicular lobe, tip of neuroacicula not penetrating epidermis.

Notochaetae flattened, short, few (two observed), with spines on convex side, smooth on straight side, with pointed tips ( Fig. 10E). Neurochaetae all missing.

Nephridial papillae not seen. Ventral keel present on last segments.

Remarks: The sampled specimens belong to Bathypolaria and share many characters with the single species described in this genus ( Bathypolaria carinata ): short body (15 segments), flattened notochaetae and ventral keel at the posterior end. However, the specimens are in poor condition and did not allow for thorough species differentiation or formal description. Based on genetic material, two MOTUs can be found in the area. Furthermore, the average K2P distance for interspecies variation was 23.4% for COI and 15.3% for 16S, confirming the presence of two species. However, Bathypolaria sp. 173 was widely distributed (BGR, IOM and GSR), whereas Bathypolaria sp. 608 was restricted to APEI#3 area.

Genetic data: DNA sequencing for this species was successful for COI (only one specimen), 16S and 18S. The specimens shared at least 99.5% and 99.9% of genetic material in 16S and 18S genes, respectively. The average K2P distance for intraspecific variation was 0.3% for 16S.

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