Terebellides ceneresi Lavesque & Hutchings & Daffe & Nygren & Londoño-Mesa 2019, n. sp.

Terebellides ceneresi n. sp.

Figures 5–6, Table 2

Type material: Holotype: MNHN-IA-TYPE 1863, complete, Northeast Atlantic Ocean, Bay of Biscay, P34, 43°33’31’’N, 1°43’49’’W, 112 m depth, May 2018; Paratypes: MNHN-IA-TYPE 1864, one specimen, complete, Northeast Atlantic Ocean, Bay of Biscay, P36, 43°34’58’’N, 1°42’01’’W, 126 m depth, May 2018; AM W.51400, one specimen, complete, Northeast Atlantic Ocean, Bay of Biscay, P37, 43°33’31”N, 1°43’49”W, 129 m depth, May 2018; MNHN-IA-TYPE 1865, one specimen, complete, Northeast Atlantic Ocean, Bay of Biscay, P36, 43°35’0”N, 1°42’02”W, 125 m depth, May 2018.

Additional material examined: SMA _BAN_11, one specimen, complete (posterior part used for molecular analysis), Mediterranean Sea, Gulf of Lion, A90, 42°32’39”N, 3°16’03”E, 90 m depth, April 2018, mounted for SEM; SMA _BAN_20, one specimen, complete, Mediterranean Sea, Gulf of Lion, Ibis 183, 42°30’30”N, 3°09’06”E, 40 m depth, December 2018; SMA _BAN_03, one specimen, complete, gravid, Mediterranean Sea, Gulf of Lion, A90, 42°32’40”N, 3°16’05”E, 90 m depth, August 2010, mounted for SEM; SMA _BR_34, incomplete, Northeast Atlantic Ocean, Brittany, Bay of Brest, ZC, 48°18’55” N, 4°21’53” W, 5 m depth, May 2018; AM W.51401, one specimen, complete, gravid, Mediterranean Sea, Gulf of Lion, A90, 42°32’40”N, 3°16’05”E, 90 m depth, August 2010; AM W.51402, one specimen, incomplete, Mediterranean Sea, Gulf of Lion, A90, 42°32’39”N, 3°16’03”E, 90 m depth, April 2018.

Description. Small species, holotype 14.2 mm long (14.2–16.5 mm) and 1.1 mm (0.8–1.1 mm). Body tapering posteriorly with segments becoming increasingly shorter and more compacted towards pygidium.

Prostomium compact; eyespots absent; large upper lip surrounding mouth with many buccal tentacles (Fig. 5B, D). Buccal tentacles of 2 types, short cylindrical and very long tentacles, spatulate (Fig. 5D). Lower lip forming an expanded structure below upper lip. SG 1 and 2 short, only visible ventrally; following segments with lobes as ventral collars (Fig. 5D). Lateral lappets on SG 3–7 (TC 1–5), continuing ventrally, largest on TC 1–4 and declining in size posteriorly (Figs 5 A–C). No conspicuous dorsal rounded projection on anterior chaetigers. Glandular lateral region absent on TC 3 (Fig. 5C).

Branchiae arising as a single structure from TC 1, reaching TC 7 (TC 8), consisting of a single elongate and annulated stalk placed mid-dorsally (Figs 5 B–C & 6A), two pairs of lobes, not fused, lower pair narrower (Fig. 6A). Upper lobes with about 25 tightly packed lamellae (Figs 5A & 6A). Both sides of branchial lamellae provided with several parallel rows of cilia and tufts of cilia on outer edge (Fig. 6 A–B). Branchiae provided without any papillar projections pointing over the edge of the branchial lamellae (Fig. 6B). Distal region of lower lobes with short terminal pointed projections (Fig. 6A). Anterior branchial projection (5 th lobe) absent (Fig. 6A).

Eighteen pairs of thoracic notopodia (SG 3–20). First notopodium on TC 1 well-developed, same size as on subsequent notopodia, notopodia placed in a straight line; notochaetae from TC 1 much smaller (or absent) than following notochaetae (Figs 5 A–C & 6A). All notochaetae simple capillaries, arranged in two rows. Neuropodia present as sessile pinnules from TC 6 (SG 8) to pygidium; uncini arranged in single rows from TC 7. First thoracic neuropodium (TC 6) provided with about five to six sharply bent acute tipped, geniculate chaetae. All subsequent thoracic neuropodia with 7–10 uncini per torus arranged in one irregular row. Uncini as shafted denticulate hooks provided with long, thin and pointed main fang appearing bent terminally giving an ‘eagle head’ appearance (Fig. 6C). Three or four teeth above the main fang, surmounted by a row of four to five short denticles and an upper crest of several smaller denticles (Fig. 6C). About 30 abdominal neuropodia as erect pinnules paddle-shaped with entire margin provided with about 20 uncini; each with four to six pointed teeth above main fang, surmounted by a row of four or five short pointed teeth and an upper crest of minute teeth (Fig. 6D).

Nephridial papillae not seen. Pygidium blunt, as a funnel-like depression.

Methyl green staining pattern. First 10 TC stain solid, except TC 4 much lighter (Fig. 5D); TC 11 and TC 12, stain with distinct stripes, fading towards posterior thoracic region (without staining, first four chaetigers slightly lighter than following ones) (Fig. 5D).

Etymology. The species is named in honour of the CNRS (French National Center for Scientific Research) that celebrates, in 2019, 80 years since its foundation.

Habitat. Mud to sandy mud, from 90 to 140 m depth, coastal maerl (rhodolith) beds.

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

Distribution. Northeast Atlantic Ocean (Bay of Biscay), Western Mediterranean Sea (Gulf of Lion), France (Fig. 1).

Remarks. Terebellides ceneresi n. sp. is very similar to specimens of T. gracilis from the Adriatic Sea (Parapar et al. 2013), in being of small size, without rounded dorsal projection or glandular region in CH 3, the absence of notochaetae on first chaetiger in smaller specimens and short notochaetae on first chaetiger for larger ones and in having the same very distinctive MG staining pattern. The two species differ only by the presence of an ‘eagle head’ appearance of thoracic uncini of T. ceneresi. However, T. ceneresi n. sp. is clearly different from the holotype of T. gracilis (Parapar et al., 2011). Indeed, T. gracilis is a larger species (32 mm vs 16 mm for gravid specimens of T. ceneresi n. sp.), with a 5 th lobe present (absent in T. ceneresi n. sp.), with up to 22 uncini in thoracic chaetigers (instead of 8 in T. ceneresi n. sp.), with posterior region of lobes with pointed projections (instead of absence or very short projections in T. ceneresi n. sp.), with MG compact colouration from CH 1 to CH 10 (instead of whitish bands from CH 1 to CH 4, especially on CH 4 in T. ceneresi n. sp.) (Table 2).

Molecular results, based on material available for this study, show that T. ceneresi n. sp. appears to be absent from Northern waters (Fig. 23).