Terebellides parapari, 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 : 173-176

Terebellides parapari n. sp.

Figures 15–16 , Table 2

Type material: Holotype: MNHN-IA-TYPE 1884, complete specimen, gravid, Northeast Atlantic Ocean , Bay of Biscay, P40, 43°33’26’’N, 1°41’37’’W, 112 m depth, May 2018 ; Paratypes: MNHN-IA-TYPE 1885, one complete specimen, Northeast Atlantic Ocean , Bay of Biscay, P37, 43°33’31”N, 1°43’49”W, 129 m depth, May 2018 ; MNHN- IA-TYPE 1886, one complete specimen, Northeast Atlantic Ocean , Bay of Biscay, P31, 43°38’40”N, 1°35’05”W, 86 m depth, May 2018 ; MNHN-IA-TYPE 1887, one complete specimen, Northeast Atlantic Ocean , Bay of Biscay, P40, 43°33’26’’N, 1°41’37’’W, 112 m depth, May 2018 ; MNHN-IA-TYPE 1888, two complete specimen, Northeast Atlantic Ocean , Bay of Biscay, P40, 43°33’26’’N, 1°41’37’’W, 112 m depth, May 2018 , mounted for SEM; AM W.51403, 4 complete specimens (2 of them gravid), Northeast Atlantic Ocean , Bay of Biscay, P35, 43°36’35”N, 1°40’35”W, 120 m depth, May 2018 ; AM W.51404, 3 complete specimens (2 of them gravid), Northeast Atlantic Ocean , Bay of Biscay, P36, 43°35’0”N, 1°42’02”W, 125 m depth, May 2018 .

Description. Small species, holotype 13.4 mm long (6.2–14.1 mm) and 0.9 mm (0.6–0.9 mm). Body tapering posteriorly with segments becoming increasingly shorter and more compact towards pygidium.

Prostomium compact; eyespots absent; upper lip with single anteriorly elongated projecting lobe surrounding mouth with many buccal tentacles ( Figs 15C & 16A ). Buccal tentacles of two types, uniformly cylindrical and with expanded tips, spatulate ( Fig. 16B ). Lower lip forming an expanded structure below upper lip ( Fig. 15C ). SG 1 and 2 short, only visible ventrally; following segments with lobes as ventral collars ( Figs 15 A–C & 16B). Lateral lappets on SG 3–7 ( TC 1–5), continuing ventrally in TC 1–5 ( Figs 15C & 16B ), largest on TC 1–3 and declining in size posteriorly. No conspicuous dorsal rounded projection on anterior chaetigers. Small round glandular region on TC 3, situated latero-dorsally ( Fig. 15C ).

Branchiae arising as a single structure from TC 1, reaching TC 4 ( TC 5), consisting of a single elongate and annulated stalk placed mid-dorsally ( Figs 15 A–C & 16A, C), two pairs of lobes, not fused, lower pair thinner ( Figs 15B & 16A, C ). Upper lobes with about 20 widely spaced lamellae ( Figs 15C & 16A, C ). Branchial lamellae, with mid-dorsal pointed tip ( Fig. 16 C–D), with sparse tufts of cilia. Branchiae provided without any papillar projections pointing over margins of the branchial lamellae ( Fig. 16 C–D). Distal region of upper lobes with small terminal pointed projections, lower lobes with short filaments ( Figs 15 A–C & 16A–C). Anterior branchial projection (5 th lobe) absent ( Fig. 16A, C ).

Eighteen pairs of thoracic notopodia ( SG 3–20). First notopodium on TC 1 well-developed, same size than subsequent notopodia; TC 1 and TC 2 situated more dorsally; notochaetae from TC 1 longer than notochaetae from TC 2, notochaetae from TC 2 longer than following ones ( Figs 15C & 16B ). 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 three to four sharply bent acute tipped, geniculate chaetae.All subsequent thoracic neuropodia with about 10–12 uncini per torus arranged in one irregular row. Uncini as shafted denticulate hooks provided with long, thin and pointed main fang, straight terminally. Two to four teeth above the main fang, surmounted by a row of three to five short teeth and an upper crest of several minute denticles ( Fig. 16E ). About 30 abdominal neuropodia as erect pinnules paddle-shaped with entire margin provided with about 15 uncini; uncini with three or four pointed teeth above main fang, surmounted by a row of three short pointed teeth and an upper crest of minute teeth ( Fig. 16F ).

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

Methyl green staining pattern. First 4 TC stain solid; from TC 5 to about TC 11, stain stripped with space between stripes pale blue. Ventral part of TC 4 stain darker ( Fig. 15C ). Presence of transverse diagonal white lines on lateral part of first three chaetigers ( Fig. 15C ). Glandular region whitish.

Etymology. The species is named after Dr. Julio Parapar, for his many contributions to the taxonomy of the Terebellides genus, especially in European waters and for his friendship.

Habitat. Mud to sandy mud, around 120 m depth.

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

Distribution. Only known from type locality ( Fig. 1 ).

Remarks. Terebellides parapari n. sp. is similar to T. shetlandica in having a relatively small size ( T. shetlandica : 6–19 mm vs T. parapari n. sp.: 8–23 mm), lobes free from each other and filaments in each of lower lobes. Nevertheless, these filaments are much longer for T. shetlandica (about ½ of length of lower lobe for T. shetlandica , instead of less than ¼ of length for T. parapari n. sp.). These two species also differ by the presence of glandular region for T. parapari n. sp. (absent in T. shetlandica ), absence of dorsal papillae on each thoracic and abdominal chaetiger for T. parapari n. sp. (present in T. shetlandica ), by the size of notochaetae (longer on the first chaetiger for T. parapari n. sp., same length for T. shetlandica ), by the shape of branchial lamellae (rounded for T. shetlandica and pointed for T. parapari n. sp.) and absence of cilia on branchial lamellae for T. parapari n. sp. (instead of presence of rows and tufts of cilia in T. shetlandica ). Finally, these two species differ by the MG pattern (compact from CH 1–4 and striped from CH 5–11, with white latero-diagonal white lines on CH 1– CH 3 for T. parapari n. sp. vs compact from TC 1–6 and striped from CH 7–12 for T. shetlandica ) ( Table 2 ).

Figures

FIGURE 1. Schematic distribution of the different Trichobranchidae species along the French coasts. Text in italic represents type locality of new species. Abbreviation: WGMP, West Gironde Mud Patch.

FIGURE 15. Terebellides parapari n. sp. paratype MNHN-IA-TYPE 1885 (A), holotype MNHN-IA-TYPE 1884 (B) and paratype MNHN-IA-TYPE 1886 (C). A. Entire worm, lateral view; B. Entire worm, lateral view, methyl green staining; C. Anterior part, lateral view, methyl green staining. Abbreviation: glr, glandular lateral region. Scales: 0.5 mm.

FIGURE 16. Terebellides parapari n. sp. SEM paratype MNHN-IA-TYPE 1888 (2 individuals). A. Anterior part, dorsal view (indiv1); B. Anterior part, lateral view (indiv2); C. Branchial lobes, dorsal view (indiv1); D. Detail of branchial lamellae, dorsal view (indiv1); E. Uncini, thoracic chaetiger (indiv1); F. Uncini, abdominal chaetiger (indiv2). Arrow indicates notochaetae of TC1 Scales: A–B=400 µm, C=250 µm, D=50 µm, E=10 µm, F=15 µm.