Bathyedithia retierei, 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 : 580-581

BATHYEDITHIA RETIEREI SP. NOV.

( FIG. 6A–G; TABLES 1, 2)

Type material: Holotype, MNHN-IA-TYPE 1814 ( IFR451 b), complete, length 3.81 mm, width 0.71 mm, 20 segments (including tentacular segment), Equatorial Eastern Pacific Ocean , Clarion-Clipperton Fracture Zone, Ifremer license area, station 158, collected 15 April 2015, epibenthic sledge supranet, 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 (based on holotype): Holotype complete, 3.81 mm long and 0.71 mm wide for 20 segments (including tentacular segment), dorsoventrally flattened, posteriorly tapering; live specimen bluish, transparent ( Fig. 6A); ethanol-preserved specimen pale white.

Prostomium bilobed, wider than long, anteriorly rounded, lobes not developed; frontal filaments absent; median notch between prostomial lobes narrow and shallow ( Fig. 6A, B); eyes absent. Median and lateral antennae absent. Palps smooth, tapering into thin tips, short (reaching to segment 2–3), inserted on rounded palpophores ( Fig. 6B). Facial tubercle absent.

Tentacular segment fused to prostomium, with a pair of short lobes, inserted laterally and slightly ventral to prostomium; without acicula or chaetae; tentaculophores distinct, bulbous, equal sized; styles smooth, tapering into thin tips, short (reaching to segment 4), dorsal and ventral tentacular cirri of similar length ( Fig. 6B). Pharynx dissected, with seven pairs of subtriangular distal papillae of similar size; two pairs of jaws with main fang, serrated margin (one pair of jaws with nine to 11 teeth and the other pair with 13 teeth; Fig. 6C). Second segment with elytrophores, subbiramous parapodia, chaetae and ventral cirri.

Ten pairs of distinct, knob-like elytrophores present on segments 2, 4, 5, 7, 9, 11, 13, 15, 17 and 19 (elytron still attached on segment 7); elytra very small (approaching the margins of preceding and subsequent segments, covering notopodia), smooth margin; surface with sparse, rounded microtubercles.

Cirrigerous segments with distinct, small dorsal cirrophores ( Fig. 6D), inserted subdistally on notopodia; styles of dorsal cirri smooth, tapering into thin tips, short (as long as tip of neuroacicular lobe); dorsal tubercles absent.

Segment 6–8 without any structures.

Ventral cirri smooth, tapering into thin tips, 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, style short (shorter than tip of neuroacicular lobe).

Parapodia subbiramous; notopodia reduced, much shorter than neuropodia ( Fig. 6D). Notopodia narrow, subtriangular, tapering into short acicular lobe, tip of notoacicula not penetrating epidermis. Neuropodia large, lanceolate, tapering into long acicular lobe, tip of neuroacicula not penetrating epidermis. Notochaetae very few (one or two observed), short, slender, slightly curved with distinct, faint spinous rows on convex side, with blunt tips preceded by smooth margin ( Fig. 6E); notochaetae more slender than neurochaeta. Neurochaetae of two types: (1) variable in number (three to 20 observed), long, distally flattened to concave, serrated along both margins, with abrupt pointed tips ( Fig. 6F); and (2) middle group mostly in anterior segments, few (five observed), slightly stouter, long, distally flattened to concave, coarsely serrated along both margins, with blunt tips ( Fig. 6G). The neurochaetae present a central rib that is more or less evident.

Nephridial papillae present on segments 10 and 11, small, digitiform. Pygidium rounded, not enclosed by last segment; with terminal anus ( Fig. 6A). Anal cirri lost, scars not seen.

Remarks: The new species is very close to Polaruschakov species having seven pairs of pharyngeal papillae, but even closer to Bathyedithia in having serrated jaws and rounded palpophores. Bathyedithia retierei sp. nov. differs from the two other species of Bathyedithia in having seven pairs of pharyngeal papillae and lanceolate neuropodia. Furthermore, in Bathyedithia retierei sp. nov. the nephridial papillae are present on segments 10 and 11, whereas in Bathyedithia tuberculata they are present from segment 7 to the end of the body, and they are absent in Bathyedithia berkeleyi .

Etymology: This species is dedicated to Professor Christian Retière (Muséum National d’Histoire Naturelle, Dinard, France) for his many contributions to French benthic research.

Genetic data: DNA sequencing for this species was successful for 16S and 18S (only 720 bp) but not for COI.

Distribution: Only one specimen was sampled at a single station within the Clarion-Clipperton Fracture Zone in Ifremer license area (type locality).