Trichobranchus demontaudouini n. sp.

Figures 21–22

Type material: Holotype: MNHN-IA-TYPE 1894, one complete specimen, Northeast Atlantic Ocean, Bay of Biscay, P40, 43°33’26’’N, 1°41’37’’W, 112 m depth, May 2018 ; Paratypes: MNHN-IA-TYPE 1895, one incomplete specimen, Northeast Atlantic Ocean, Bay of Biscay, P40, 43°33’26’’N, 1°41’37’’W, 112 m depth, May 2018 , mounted for SEM; MNHN-IA-TYPE 1896, one incomplete specimen, Northeast Atlantic Ocean, Bay of Biscay, P37, 43°33’31”N, 1°43’49”W, 129 m depth, May 2018 .

Additional material: SMA _ Tricho _22, incomplete, Northeast Atlantic Ocean, Northern Bay of Biscay, APP D3, 47°28’21” N, 03°29’35” W, 72 m depth, May 2018 , mounted for SEM; AM W.52080, incomplete, Northeast Atlantic Ocean, Northern Bay of Biscay, APP D3, 47°28’21”N, 03°29’35”W, 72 m depth, May 2018 ; SMA _ Tricho _ 25, incomplete, Northeast Atlantic Ocean, Northern Bay of Biscay, APP D1, 47°28’48”N, 03°39’20”W, 72 m depth, May 2018 ;

Description. Medium size species, holotype with length of 30.4 mm and width of 1.8 mm (1.2–1.6 mm), thorax cylindrical, abdomen tapering (Fig. 21A).

Prostomium well developed, distal part extending transversely across base of upper lip, trilobed, with buccal tentacles originating laterally and mid-dorsally; long buccal tentacles of two types, thin and cylindrical, and thick and grooved (Fig. 22B); eyespots present as two groups forming two dorsolateral bands situated on prostomium above origin of buccal tentacles (Fig. 21 A–C). Peristomium with one pair of large ventrolateral flaring lobes (Fig. 21A), with ciliary ridges, midventrally fused to lower lip; lower lip short, upper lip hidden by buccal tentacles. Segment 1 dorsally inconspicuous, ventrally forming semicircular eversible process (Fig. 21D). SG 2–4 with ventral crests anteriorly raised, larger than following ones; following segments with short ventral crests (Fig. 21D). Dorsum smooth. Ventral groove absent. Two pairs of branchiae, on segments 2 and 3 (Figs 21 B–C & 22A–B), each pair with single long filament; filaments annulated, highly fragile (filament of second pair of holotype regenerating) (Fig. 21B), second pair originating slightly dorsally to first pair (Fig. 22B).

Notopodia starting from SG 6, extending for 15 segments, trapezoidal shaped; first three pairs shorter than subsequent ones, laterally aligned; narrowly-winged long bilimbate notochaetae, with narrow limbation on both margins. Neuropodia starting from SG 6, thoracic neuropodia with 15 to 25 uncini per torus arranged in one irregular row; uncini with strong, distally blunt main fang and many rows of secondary teeth, presence of a sheath below main fang (Fig. 22C). About 65 abdominal neuropodia as erect pinnules, paddle-shaped with distal margin provided with about 35 uncini; uncini with three rows of pointed secondary teeth above and laterally to main fang, surmounted by an upper crest of minute teeth (only visible with SEM) (Fig. 22D). Pygidium with two short bulbs (Fig. 21A).

Remarks. In European waters, Trichobranchus demontaudouini n. sp. can be easily differentiated from T. gla- cialis by the presence of two pairs of branchiae, instead of three pairs. In this character, T. demontaudouini n. sp. is similar to T. roseus . However, T. roseus is characterized by the absence of eyespots and many secondary teeth on abdominal uncini (Holthe 1986:167, fig.78d; Nogueira 2008).

Etymology. The species is named after Dr. Xavier de Montaudouin, for his friendship, his permanent support and for his many contributions to French benthic research.

Habitat. Mud to sandy mud, 110–130 m depth.

Type locality. Near Capbreton Canyon, Bay of Biscay, Northeast Atlantic Ocean, France .

Distribution. Bay of Biscay, near Capbreton Canyon to South Brittany (Fig. 1).