Streblosoma cabiochi Lavesque & Londoño-Mesa & Daffe & Hutchings 2020, n. sp.

Streblosoma cabiochi n. sp.

Figures 4–5

urn:lsid:zoobank.org:act: 51245F7C-1561-4528-84E9-60E9CCA68E3F

Material examined: Holotype: MNHN-IA- type 2000, one specimen, incomplete, English Channel, Brittany, Morlaix Bay, Pierre Noire, 48°42’30”N 3°51’58”W, 17 m depth, March 2019. Paratypes: AM W.53066, one specimen, incomplete, English Channel, Brittany, Morlaix Bay, Pierre Noire, 48°42’30”N 3°51’58”W, 17 m depth, October 2014, mounted for SEM; MNHN-IA- type 2001, one specimen, incomplete, English Channel, Brittany, Morlaix Bay, Pierre Noire, 48°42’30”N 3°51’58”W, 17 m depth, March 2019; MNHN-IA- type 2002, one specimen, incomplete, English Channel, Brittany, Morlaix Bay, Pierre Noire, 48°42’30”N 3°51’58”W, 17 m depth, March 2019; AM W.53067, one specimen, incomplete, English Channel, Brittany, Morlaix Bay, Pierre Noire, 48°42’30”N 3°51’58”W, 17 m depth, March 2019.

Additional material. SMA_ROS-Streblo-06, one specimen, incomplete, English Channel, Brittany, Morlaix Bay, Pierre Noire, 48°42’30”N 3°51’58”W, 17 m depth, October 2014. SMA_BR-Streblo-02, one specimen, incomplete, Northern Bay of Biscay, B3_APP1, 47°31’27”N 3°27’02”W, 52 m depth, May 2018.

Description. Large species, holotype incomplete (33 segments), 34.0 mm long (24.3–49.6), 1.3 mm wide (1.2– 2.0).

Transverse prostomium attached to dorsal surface of upper lip; basal part with eyespots irregularly arranged in two separated lateral areas (Fig. 4C), distal part of prostomium strongly shelf-like. Short and thick grooved buccal tentacles (Fig. 4C). Peristomium forming lips; upper lip hood-like, slightly convoluted, broader than high (Figs 4 B–C; 5A–B); lower lip short, hidden by expanded lobe derived from SG1, lobe broader than high (Figs 4 B–C; 5A–C). SG1 short, visible dorsally and ventrally. Presence of a short lateral crest on SG2, covering SG1 laterally (Figs 4C; 5A).

Three pairs of branchiae, on SG2–4, SG2 with 5–8 filaments on either side, SG3 with 5–8 filaments on either side and SG4 with 5–7 filaments on either side (Figs 4A, C; 5C); branchial filaments thin, originating from body wall, dorsally to notopodia, not from cushion-like structure, with wide medial gap (Figs 4A; 5C); longest filaments about as long as body width at corresponding segment (Fig. 5C). Anterior ventral surface strongly glandular from SG2 to about SG12 (Fig. 4B), ventral shields absent, mid-ventral groove visible from about SG13 to end of specimen (Fig. 4B).

Notopodia from SG2 and extending until end of incomplete specimens (SG62 for paratype MNHN-IA- type 2002); first pair of notopodia shorter than following ones; first notopodia oriented dorsally (from CH 1 to about CH 8), moving progressively to lateral position (Figs 4C; 5A); notopodia large, roughly rectangular, distally rounded (Figs 4A; 5C), bilobed with notochaetae arising between lobes. Notochaetae in two rows, increasing in length from ventral to dorsal position. Notochaetae narrowly-winged, wings only present at tips, those of anterior row much shorter than those of posterior row (about 1/5 of the length) (Fig. 5 D–E).

Neuropodia from SG5, first ones as fleshy ridges, progressively raised from surface of body. Uncini in straight rows until end of specimens (incomplete). Uncini with two rows of secondary teeth above the main fang, basal row with 2 teeth, second row with irregularly sized teeth, dorsal button relatively close to anterior margin, conspicuous prow, conspicuous heel, base strongly curved; uncini as long as high (Figs 4D & 5F).

Nephridial and genital papillae not visible. Pygidium unknown. Tubes made of coarse sand.

Etymology. The species is named after Dr. Louis Cabioch, for his many contributions to the benthic ecology and the exploration of the seabed of the English Channel. This species name was chosen in agreement with Céline Houbin and Eric Thiébaut, from the Station Biologique de Roscoff, who sent us the type material.

Habitat. Fine sands, 17 m depth; coastal maerl (rhodolith) beds, 1–5 m depth.

Type locality. Morlaix Bay, English Channel, France.

Distribution. Bay of Biscay (Bay of Brest), English Channel (Morlaix Bay).

Remarks. This new species is characterized by the presence of three pairs of branchiae and the absence of uncini in C-shaped loops from mid thorax. S. cabiochi n. sp. is similar to two European species: S. bairdi (Malmgren, 1866) and S. intestinale M. Sars in G.O Sars, 1872. However, S. cabiochi n. sp. differs from S. intestinale by the numbers of branchial filaments with 5–8 filaments on SG2, 5–8 on SG3 and 5–7 on SG4 (instead 3–5, 2–3 and 0–3 respectively for S. intestinale). Streblosoma cabiochi n. sp. also differs from S. bairdi by the shape of lateral crest on SG2 (small for S. cabiochi n. sp., protruding for S. bairdi), the absence of glandular pads where branchial filaments are inserted (present on S. bairdi) and the shape of uncini as long as high, with a strongly curved base and two rows of secondary teeth in S. cabiochi n. sp., longer than high, with slightly curved base and three well defined rows of secondary teeth in S. bairdi.