Yodanoe 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 : 620-623

YODANOE SP. 659-3

( FIG. 22; TABLES 1, 2)

Material examined: MNHN-IA-PNT 73 ( IFR659-3 ), complete, length 3.27 mm, width 0.50 mm, 15 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 .

Description: Complete, 3.27 mm long and 0.50 mm wide for 15 segments (including tentacular segment), dorsoventrally flattened, tapering posteriorly; colour of live animal not known; ethanol-preserved specimen pale white, prostomium white; most of chaetae lost ( Fig. 22).

Prostomium bilobed, about as wide as long, lobes pronounced, anteriorly tapering to triangular peaks, located close to the notch; frontal filaments absent; median notch between prostomial lobes wide and moderately deep ( Fig. 22); eyes absent. Median antenna present, lateral antennae absent; ceratophore of median antenna large, cylindrical, as long as prostomium lobes), inserted anteromedially on prostomium, in the notch; style missing. Palps smooth, tapering, very long (reaching around segment 7; Fig. 22). Facial tubercle absent; upper lip with bilobed folds.

Tentacular segment with elongate acicular lobe, inserted laterally and slightly ventral to prostomium; with acicula not penetrating epidermis, without chaetae; tentaculophores distinct, large; dorsal tentacular style missing; ventral tentacular style thin, tapering into thin tip, smooth, long (reaching segment 5). Pharynx not everted, dissected with nine pairs of distal equal-sized, subtriangular papillae; two pairs of jaws, each with main fang with a small elevation as secondary tooth. Second segment with elytrophores, subbiramous parapodia, with chaetae and ventral cirri.

Probably eight pairs of bulbous to massive, cylindrical elytrophores, present on segments 2, 4, 5, 7, 9, 11, 13 and 15; elytra still attached on segment 2, translucent, rounded, almost entire margin papillated, microtubercles not seen. Dorsal ridges pronounced (V shape).

Cirrigerous segments with distinct, cylindrical dorsal cirrophores, inserted subdistally on notopodia; style missing; dorsal tubercles present, forming cirriform branchial-like processes, small on segment 3, becoming longer from segment 6 (as long as elytrophores; Fig. 22).

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

Parapodia subbiramous; notopodia shorter than neuropodia. Notopodia arising from dorsum as two thickened ridges; notopodia narrow, subtriangular, tapering into long acicular lobe, tip of notoacicula not penetrating epidermis. Neuropodia large, rectangular to subtriangular, tapering into long acicular lobe, tip of neuroacicula not penetrating epidermis. Notochaetae short to long, slender, slightly curved, with developed spinous rows on convex side, with blunt tips; notochaetae as stout as neurochaetae. Neurochaetae distally flattened to concave, serrated along both margins, with pointed tips.

Nephridial papillae absent. Pygidium rounded, not enclosed by last parapodia; with dorsal anys. Anal cirri lost, scars not seen.

Remarks: The present specimen is in too poor condition to be described as a new species, but it was used to describe the pharynx for this genus. See Remarks on Yodanoe desbruyeresi gen. nov., sp. nov. for more details.

Genetic data: DNA sequencing for this species was successful for COI and 16S but not for 18S.

Distribution: Only one specimen was sampled at a single station within the Clarion-Clipperton Fracture Zone in APEI#3 area.

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