Thelepus corsicanus Lavesque & Londoño-Mesa & Daffe & Hutchings 2020, n. sp.
Creators: name: Lavesque, Nicolas
name: Londoño-Mesa, Mario H.
name: Daffe, Guillemine
name: Hutchings, Pat
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Terebellida
Terebellidae
Thelepus
Thelepus corsicanus

description: Thelepus corsicanus n. sp.   
Figures 7–8  
urn:lsid:zoobank.org:act: AC447498-A085-4BF0-8DE4-49B0138E3930  
 Material examined: Holotype: MNHN-IA- type 2003, incomplete, Mediterranean Sea, Corsica Cape, CR 37, 42°44’47”N 9°28’06”E, 21 m depth, May 2019, some parapodia used for molecular analyses and some parapodia mounted for SEM. Paratypes: MNHN-IA- type 2004, complete, Mediterranean Sea, Corsica Cape, CB03, 42°43’00”N 9°15’54”E, 29 m depth, May 2019, parapodia used for molecular analyses, AM W.53068, incomplete, Mediterranean Sea, Corsica Cape, CS16, 42°46’12”N 9°20’00”E, 22 m depth, May 2019, mounted for SEM. AM W.53069, incomplete, Mediterranean Sea, Corsica Cape, CB03, 42°43’00”N 9°15’54”E, 29 m depth, May 2019, mounted for SEM. AM W.53070, complete, Mediterranean Sea, Corsica Cape, CS25, 42°44’42”N 9°28’00”E, 16 m depth, May 2019.   
 Additional material: SMA_COR_ Thele _05, incomplete, Mediterranean Sea, Corsica Cape, CS25, 42°44’42”N 9°28’00”E, 16 m depth, May 2019, parapodia used for molecular analyses. AM W.53071, incomplete, Mediterranean Sea, Corsica Cape, CS25, 42°44’42”N 9°28’00”E, 16 m depth, May 2019, mounted for SEM. SMA_COR_ Thele _09, incomplete, Mediterranean Sea, Corsica Cape, CS25, 42°44’42”N 9°28’00”E, 16 m depth, May 2019.   
 Description. Holotype incomplete (51 segments) 37 mm long, 1.8 mm wide, paratypes very small (4.1–9.3 mm long, 0.6–1.01 mm wide).   
Prostomium at base of upper lip; eyespots in thin and continuous discrete band (Fig. 7C); buccal tentacles very thick, deeply grooved, reaching ~SG16, leaving deep notches on prostomium (Figs 7 A–D; 8A–B). Upper lip distinctly wider than long, not convoluted, thick, hood-like (Figs 7 A–B, D; 8B); lower lip thick, surrounded by ventral crescent-shaped lobe originating from SG1 (Figs 7 A–B, D; 8B). SG1 short, more visible dorsally, except for ventral lobe, SG2 with antero-lateral crest.  
Two pairs of branchiae, on SG2–3, with 10 (2–3) filaments on SG2 and 6–7 (1) on SG3 (Figs 7A, C; 8A); filaments short, distally blunt, cylindrical, arising directly from body wall, with wide medial gap; branchial filaments arranged in two irregular rows (Fig. 8A).  
Ventral surface of anterior segments strongly glandular, corrugated on anteriormost segments, ventral shields absent (Fig. 8B, D); mid-ventral stripe beginning from about SG22, discrete. Notopodia of incomplete holotype from SG3 to SG51, from SG3 to SG40 for complete paratype MNHN-IA- type 2004 (n=65 segments); notopodia short, roughly rectangular, distally rounded (Figs 7A, 8C), progressively shorter and more rounded from mid-body; notochaetae emerging between lobes. Few falcate notochaetae in both rows, anterior row with 8–10 (4–5) twisted winged chaetae (Fig. 8 C–D), posterior row with about 7–8 (4–5) narrowly-winged notochaetae (Fig. 8C, E); wellmarked difference in length between rows (Fig. 8C).  
Neuropodia from SG5, as long fleshy ridges on anterior body, progressively shorter and more raised from midbody segments onwards. Uncini with terminal dorsal button, short prow, much shorter than button, base curved; uncini longer than high (Fig. 7 E–F). Crest of uncini with two rows of secondary teeth, basal row with 2–3 teeth, second row with irregularly sized teeth (Fig. 8F).  
Nephridial and genital papillae not seen. Pygidium slightly crenulated (paratypes).  
 Etymology. The species name refers to the type locality and geographical distribution of this species.   
 Habitat. 16–29 m depth, among rocks (collected by scuba divers).   
 Type locality. Corsica Cape, Mediterranean Sea.   
 Distribution. Known only from type locality.   
 Remarks. Molecular analyses (Figs 11; 12) allowed us to confirm that all specimens from Corsica belong to a single species. Indeed, K2P distances for 16S were equal to 1% between holotype (MNHN-IA- type 2003) and other small type material. The number of branchial filaments is clearly size-dependent with 10 filaments on SG2 and 6–7 on SG3 for holotype, and only 2–3 and one, respectively for other small specimens. As holotype is incomplete and paratypes are all small individuals, it is not possible to state where notopodia terminate along the body (at least 49 segments on holotype, and on 60% of the body length for small specimens).   
 Among the European species, T. corsicanus n. sp. is similar to T. davehalli Jirkov, 2018, described from off the Faroe Islands, in having two pairs of branchiae and the absence of uncini forming a loop after SG14. However, these two species can be easily differentiated by the presence of eyespots in T. corsicanus n. sp. (absent in T. davehalli), the number of branchial filaments on SG2 (~10 for T. corsicanus n. sp., ~20 for T. davehalli), the absence of a convoluted upper lip for T. corsicanus n. sp. (a priori present for T. davehalli, but not reported in the description of this species, see Fig. 4B in Jirkov 2018), the shape of uncini (crest with three rows of teeth for T. corsicanus n. sp., crest with a priori only one row of teeth for T. davehalli, see Fig. 4 G–H in Jirkov 2018) and the geographical distribution (Corsica, Mediterranean Sea for T. corsicanus n. sp., NE Atlantic shelf for T. davehalli).
description: Published as part of Lavesque, Nicolas, Londoño-Mesa, Mario H., Daffe, Guillemine & Hutchings, Pat, 2020, A revision of the French Telothelepodidae and Thelepodidae (Annelida Terebelliformia), with descriptions of three species and first European record of a non-indigenous species, pp. 305-327 in Zootaxa 4810 (2) on pages 317-318, DOI: 10.11646/zootaxa.4810.2.4, http://zenodo.org/record/3938264