Terebellides ramili, Parapar & Martin & Moreira, 2020

Parapar, Julio, Martin, Daniel & Moreira, Juan, 2020, On the diversity of Terebellides (Annelida, Trichobranchidae) in West Africa, seven new species and the redescription of T. africana Augener, 1918 stat. prom., Zootaxa 4771 (1), pp. 1-61 : 43-45

Terebellides ramili sp. nov.

Figures 11D , 28B , 33 , 34 , 37 ; Tables 1, 2 urn:lsid:zoobank.org:act:97DCCE83-A2BC-48EF-B84A-BB20123827AF

Material examined. Type material. Four specimens: holotype ( MNCN16.01 /18615); three paratypes ( MNCN 16.01 /18613, 16.01/18614 and 16.01/18616). Non-type material. One specimen (NHMD-231438, Table 1) .

Diagnosis. Body small/medium sized (18.5 mm in length); TC1–5 ventrally whitish. Branchial anterior lobe absent; posterior ventral lobes thinner than dorsal ones, with terminal filament and directly emerging from branchial stem. TC1 notopodia and notochaetae as long as following ones. Thoracic neurochaetae with rostrum/capitium length about 1/1, and capitium with a first row of 5−6 small teeth followed by similar sized ones.

Description based on holotype

Measurements and general body features. Complete specimen, 18.5 mm long and 1.5 mm wide; female with oocytes in body cavity ( Fig. 28B , 33 A−B). Body tapering posteriorly with segments increasingly shorter and crowded towards pygidium. Prostomium compact; short tentacular membrane surrounding mouth, devoid of buccal tentacles. SGI as an expanded structure below tentacular membrane ( Fig. 33A ). Lateral lappets on SGIII–VII (TC1–5), larger in SGIII–IV ( Fig. 33B ).

Branchiae. Branchiae arising as single structure from SGIII, with a single stalked mid-dorsal branch ( Fig. 28B ) having one pair of dorsal (upper), non-fused lobes and one pair of shorter ventral (lower) lobes, neither fused together nor to dorsal ones, with terminal filament ( Fig. 28B , 33 A−B). Anterior projection of dorsal lobes (lobe 5) absent. Both sides of branchial lamellae with cilia; rows and/or tufts or papillae not seen.

Thorax. Eighteen pairs of notopodia (SGIII–XX), with those of TC1 as long as subsequent ones. Neuropodia as sessile pinnules, from TC6 (SGVIII) to pygidium, with uncini in single rows starting from TC7 (SGIX) throughout. First neuropodia (TC6) with 4–5 sharply bent, acute-tipped, geniculate chaetae ( Fig. 34A ) showing minute teeth forming a capitium. From TC7, neuropodia with up to 6–10 uncini per torus in one row, with long shafted denticulate hooks, rostrum about same length as capitium, with 8–10 small teeth above main fang, surmounted by two rows of several teeth of same size ( Fig. 34 B–D).

Abdomen. Thirty-one neuropodia as erect pinnules, with about 25−30 uncini per torus having four teeth above main fang surmounted by an upper crest of 4–5 teeth and a variable number of smaller teeth ( Fig. 34 E–F).

Other body features. Pairs of nephridial papillae both at TC1; dorsal paired nephridial openings in anterior thoracic notopodia not seen. Pygidium blunt, as funnel-like depression. Five anterior thoracic chaetigers (TC1−5) ventro-laterally whitish ( Fig. 33A ); last two (TC4–5) more pigmented.

Methyl green staining pattern. Anterior CH 1 to CH 3 solid; CH 4 to CH 12 striped; being CH 4 and CH 5 much more marked than previous ones, and CH 12 faded; J-shaped glandular region slightly marked lateral to CH 2 and CH 3; near pattern 5 of Schüller & Hutchings (2010) ( Fig. 37 ).

Variability. Body 6.0 mm long in the only complete (and probably immature) paratype (MNCN16.01/18613). Specimen NHMD-231438 ( Fig. 33C ), collected during the Galathea expedition and originally identified as T. stroemii by Kirkegaard (1959), has been identified here as T. af. ramili . It is a 22-mm long female with oocytes that was collected nearby the type location and at similar depths (Table 1). However, its identity cannot be fully confirmed as colouration of TC4–TC5 is different than others being more widely distributed in TC4 and much less in TC5 ( Fig. 33C ). Moreover, this specimen bears shorter branchial ventral lobes than in T. ramili sp. nov. and lacks terminal filament.

Type locality. Off Congo; 190 m depth (Table 1) .

Distribution and bathymetry. Off Congo and Namibia; 190−537 m depth ( Fig. 11D ; Table 1).

Etymology. The species is named after Dr. Francisco Ramil (Universidade de Vigo, Spain), for his numerous contributions to the taxonomy of marine invertebrates, especially Cnidarians, in many world seas but specifically in the Iberian Peninsula, Antarctica and the Atlantic African littoral.

Remarks. The conspicuous white colouration of T. ramili sp. nov. resembles that of the boreal Terebellides gracilis Malm, 1874 , recently reported from Iceland by Parapar et al. (2011) and the Adriatic Sea by Parapar et al. (2013). The type material redescribed by Parapar et al. (2011) shows a homogeneous colour pattern between TC1 and TC4, while in T. ramili sp. nov. it appears from TC1 to TC5 being even more conspicuous in TC4 and TC5. Furthermore, TC1 notopodia and notochaetae in the Mediterranean specimens of T. gracilis are smaller than in other chaetigers (similar throughout or slightly larger in T. ramili sp. nov.) and the thoracic uncini show large anterior teeth in the capitium ( Parapar et al., 2011: Fig. 10C ). These teeth are closer to Type 1, as it happens in T. longiseta sp. nov. and T. kirkegaardi sp. nov., or Type 2, as in T. fauveli sp. nov., and different to the Type 4 present in T. ramili sp. nov. Moreover, T. ramili sp. nov. also differs from the three aforementioned species in the branchial shape, size of TC1 and ventral colour pattern (see above).

Figures

FIGURE 10. Terebellides augeneri sp. nov. SEM micrographs of the paratype MNCN 16.01/18578. (A) row of thoracic uncini, upper view; (B) two thoracic uncini, upper-lateral view; (C) TC6 geniculate chaeta, upper view; (D) the same, capitium, detail (framed in C); (E) abdominal uncini, upper view; (F) abdominal uncini, frontal view. Circles in (B) and (E) showing number of teeth on capitium. Abbreviations: cap—capitium; ros—rostrum.

FIGURE 11. Maps of Central and Southern Atlantic African coasts showing the stations where the species of Terebellides described in this work were found. (A) T. africana stat. prom., T. augeneri sp. nov. and T. congolana sp. nov.; (B) T. fauveli sp. nov. and T. kirkegaardi sp. nov.; (C) T. longiseta sp. nov. and T. nkossa sp. nov.; (D) Terebellides sp. 1, Terebellides sp. 2 and T. ramili sp. nov.

FIGURE 28. Terebellides nkossa sp. nov. (holotype, MNCN 16.01/18594): (A) anterior end, left lateral view and detail of branchiae. Terebellides ramili sp. nov. (holotype, MNCN 16.01/18615): (B) anterior end, left lateral view and detail of branchiae. Abbreviations: bldl—branchial left dorsal lobe; blvl—branchial left ventral lobe; brdl—branchial right dorsal lobe; brvl—branchial right ventral lobe; bvltf—branchial ventral lobe terminal filament; TC—thoracic chaetiger.

FIGURE 33. (A–B) Terebellides ramili sp. nov. Stereomicroscope images of holotype MNCN 16.01/186013. (A) full specimen, right lateral view; (B) anterior end, left lateral view. Terebellides af. ramili (NHMD-231438): (C) anterior end, right lateral view. Abbreviations: bldl—branchial left dorsal lobe; blvl—branchial left ventral lobe; brdl—branchial right dorsal lobe; brvl—branchial right ventral lobe; bvltf—branchial ventral lobe terminal filament; gc—geniculate chaetae; loli—lower lip; ooc—oocytes; SG—segment; TC—thoracic chaetiger; tm—tentacular membrane.

FIGURE 34. Terebellides ramili sp. nov. SEM micrographs of the paratype MNCN 16.01/18614. (A) TC6 geniculate chaetae; (B–D) thoracic uncini in latero-frontal, lateral and upper view; (E–F) abdominal uncini, fronto-lateral view. Circle in (D) showing number of teeth on capitium. Abbreviations: cap—capitium; ros—rostrum.

FIGURE 37. Body staining patterns—following Schüller & Hutchings (2010)—in ventral view of the species described in this work; chaetigers indicated in Arabic numbers.