Terebellides ramili

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

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Terebellides ramili

sp. nov.

Terebellides ramili  sp. nov.

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

Material examined. Type material. Four specimens: holotype ( MNCN16.01View Materials /18615); three paratypes ( MNCN 16.01View Materials /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. 28BView FIGURE 28, 33View FIGURE 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. 33AView FIGURE 33). Lateral lappets on SGIII–VII (TC1–5), larger in SGIII–IV ( Fig. 33BView FIGURE 33).

Branchiae. Branchiae arising as single structure from SGIII, with a single stalked mid-dorsal branch ( Fig. 28BView FIGURE 28) 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. 28BView FIGURE 28, 33View FIGURE 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. 34AView FIGURE 34) 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. 34View FIGURE 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. 34View FIGURE 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. 33AView FIGURE 33); 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. 37View FIGURE 37).

Variability. Body 6.0 mm long in the only complete (and probably immature) paratype (MNCN16.01/18613). Specimen NHMD-231438 ( Fig. 33CView FIGURE 33), 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. 33CView FIGURE 33). 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. 11DView FIGURE 11; 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. 10CView FIGURE 10). 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).