Terebellides europaea, Lavesque & Hutchings & Daffe & Nygren & Londoño-Mesa, 2019

Lavesque, Nicolas, Hutchings, Pat, Daffe, Gullemine, Nygren, Arne & Londoño-Mesa, Mario H., 2019, A revision of the French Trichobranchidae (Polychaeta), with descriptions of nine new species, Zootaxa 4664 (2), pp. 151-190 : 163-165

Terebellides europaea n. sp.

Figures 7–8 , Table 2

Type material: Holotype: MNHN-IA-TYPE 1866, complete, Northeast Atlantic Ocean, Brittany, Bay of Brest , ZC, 48°18’55”N, 4°21’54”W, 1.3 m depth, January 2016 . Paratypes: MNHN-IA-TYPE 1867, complete specimen (posterior part used for molecular analysis), Northeast Atlantic Ocean, Brittany, Bay of Brest , VC, 48°18’59”N, 4°23’28”W, 2.2 m depth, July 2017 ; MNHN-IA-TYPE 1868, complete (posterior part used for molecular analysis), Northeast Atlantic Ocean, Brittany, Bay of Brest , ZC, 48°18’55”N, 4°21’53”W, 5 m depth, May 2018 ; MNHN-IA- TYPE 1869, complete (posterior part used for molecular analysis), Northeast Atlantic Ocean, Brittany, Bay of Brest , BK, 48°21’28”N, 4°26’38”W, 7 m depth, May 2018 , mounted for SEM.

Additional material examined: SMA _BR_10, complete (posterior part used for molecular analysis), Northeast Atlantic Ocean, Brittany, Bay of Brest , VC, 48°18’59”N, 4°23’28”W, 2.2 m depth, July 2017 . SMA _SP_10, complete, (posterior part used for molecular analysis), Northeast Atlantic Ocean, Spain, Ria de Ferrol , 43°28’N, 8°14’W, 40 m depth, June 2017 .

Description. Small size species, with holotype 16.9 mm long (15.4 mm) and 2.1 mm (1.5–2.2 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 ( Figs 7 B–D & 8A). Buccal tentacles of two types, uniformly cylindrical and with expanded tips, spatulate ( Fig. 8A ). Lower lip forming an expanded structure below upper lip ( Figs 7 A–B & 8A). S1 and S2 short, only visible ventrally; following segments with lobes as ventral collars ( Fig. 7 A–B). Lateral lappets on SG 3–6, ( TC 1–5), continuing ven- trally in TC 1–6, largest on TC 1 and 2 and declining in size posteriorly. No conspicuous dorsal rounded projection on anterior chaetigers. Postero-lateral undulating glandular region on TC 3 ( Fig. 7D ).

Branchiae arising as a single structure from TC 1 and reaching TC 6 ( TC 4), consisting of a single elongate and annulated stalk situated mid-dorsally, made up of two pairs of lobes fused on 1/2 of length, lower pair thinner ( Fig. 7C ). Posterior region of upper terminal pointed projections and of lower lobes with long pointed projections ( Fig. 7 B–C). Upper lobes provided with about 50 well packed lamellae, lamellae of different width and size ( Figs 7 B–C & 8A–B). Both sides of branchial lamellae provided with well-marked parallel rows of cilia, no tufts of cilia on outer edge ( Fig. 8 A–B). Presence of rounded papillar projections over the edge of anterior branchial lamellae ( Figs 7 B–C & 8A–B). Anterior branchial projection (5 th lobe) present ( Figs 7 A–B, D & 8A).

Eighteen pairs of thoracic notopodia ( SG 3–20; TC 1–18). Notopodia present from TC 1 well–developed; notochaetae of TC 1 slightly longer in length than following notochaetae. All notochaetae simple capillaries, arranged in two rows. Neuropodia present as sessile pinnules from TC 6 ( SG 8) to pygidium, with uncini arranged in a single row from TC 7. First thoracic neuropodia ( TC 6) provided with four (3–5) sharply bent acute tipped to almost straight, geniculate chaetae. All subsequent thoracic neuropodia with about 10–17 uncini per torus arranged in one irregular row. Uncini as shafted denticulate hooks provided with long, thin and pointed main fang, straight terminally. Three or four teeth above the main fang, surmounted by a row of five to six short denticles and an upper crest of several minute denticles ( Fig. 8C ). Abdomen with 33 neuropodia as erect pinnules paddle—shaped with entire margin provided with about 30 uncini; each with four pointed teeth above main fang, surmounted by a row of three to five short pointed teeth and an upper crest of minute teeth ( Fig. 8D ).

Two pairs of elongated nephridial papillae, located latero-posteriorly to base of each notopodium of TC 4 and TC 5. Pygidium blunt.

Methyl green staining pattern. Solid from TC 1 to TC 9, with distinct stripes from TC 10 to about TC 12, distinct white antero-ventral lines from TC 5 to TC 9; white glandular region on TC 3, with central line more intensive stained and lateral deep ridges ( Fig. 7D ).

Etymology. Species name refers to the wide distribution of the species in Europe from the south of the Bay of Biscay ( Spain) to North of Norway.

Habitat. Coastal maerl (rhodolith) beds, 2–11 m depth (this study), from mud to gravels, 8–102 m depth ( Nygren et al 2018).

Type locality. Bay of Brest , Brittany, France .

Distribution. Bay of Biscay (Bay of Brest, Trévignon, Ria of Ferrol) (this study), Kattegat, Skagerrak, North Sea, Irish Sea, Celtic Sea and Norwegian coast and shelf ( Nygren et al. 2018)

Remarks. Except T. stroemii from Adriatic Sea ( Parapar et al. 2013) (see T. lilasae n. sp. Remarks), T erebellides europaea n. sp. differs from other previously known European species by the presence of papillar projections pointing over the edge of the branchial lamellae. In this character, T. europaea n. sp. is also similar to T. bonifi n. sp., T. gentili n. sp., T. lilasae n. sp. and T. resomari n. sp. Among these species, only T. gentili n. sp., shares the same undulating glandular region on TC 3. However, these two species differ in the shape of papillar projection (widely spaced, small and elongated for T. gentili n. sp., rounded and only present on anterior lamellae for T. europaea n. sp.), by the size (<16 mm for T. europaea n. sp.,> 30 mm for T. gentili n. sp.) and the presence of terminal filaments on the lower lobes for T. europaea n. sp., (pointed projections only for T. gentili n. sp.) ( Table 2 ).

Based on 16S and COI sequences, T. europaea n. sp. is identical to clade 6 from Nygren et al. (2018, Fig. 10 ). In this study, authors suggested that this clade could be T. stroemii . However, based on our observations, we are now confident that T. europaea n. sp. is different from T. stroemii which should not be associated with clade 6. Indeed, T. europaea n. sp. differs from T. stroemii by the presence of papillar projections over the edge of anterior branchial lamellae (absence for T. stroemii ), the shape of glandular region on TC 3 (undulating with lateral ridges for T. europaea n. sp., oval for T. stroemii ), the absence of both “eagle-shaped’ thoracic uncini and rounded dorsal projection on TC 1–5 (presence for T. stroemii ) ( Table 2 ). Next step will be to define which clade corresponds to the true T. stroemii . This is complicated by the fact that Sars did not designate a holotype and the exact locality is fairly vague and we know from Nygren et al. (2018) that more than one species can occur in the same location.

Figures

FIGURE 7. Terebellides europaea n. sp. holotype MNHN-IA-TYPE 1866 (A–C), paratype MNHN-IA-TYPE 1867 (D). A. Entire worm, ventro-lateral view; B. Anterior part, lateral view; C. Anterior part, dorsal view; D. Anterior part, lateral view, methyl green staining. Abbreviation: glr, glandular lateral region. Scales: A=2 mm, B–D =1 mm.

FIGURE 8. Terebellides europaea n. sp. SEM paratype MNHN-IA-TYPE 1869A. Anterior part, lateral view; B. Papillar projections on edge of anterior branchial lamellae, lateral view; C. Uncini, thoracic chaetiger; D. Uncini, abdominal chaetiger. Scales: A=500 µm, B=250 µm, C=15 µm, D=9 µm.

FIGURE 10. Terebellides gentili n. sp. SEM paratype MNHN-IA-TYPE 1873 A. Anterior part, lateral view; B. Papillar projections on edge of branchial lamellae, lateral view; C. Uncini, thoracic chaetiger; D. Uncini, abdominal chaetiger. Scales: A=400 µm, B=90 µm, C=25 µm, D=15 µm.