Ophryotrocha nunezi, sp. nov.

Ophryotrocha nunezi sp. nov.

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Fig. 10

Etymology

The species is named after Dr Jorge Nuñez, who described several of the currently known Ophryotrocha species and first examined the specimens from the Cantabrian Sea. Dr Nuñez has always been very helpful in our requests for assistance on these taxa.

Material examined

Holotype MOROCCO • complete spec. (formalin), 0.97 mm long, 0.14 mm wide, 16 chaetigers; GoC, Mercator MV; 35°17.916′ N, 06°38.709′ W; 354 m depth; 2 Mar. 2008; Stn 64PE284_12750W; wood substratum; NHMUK 2020.1514.

Paratypes MOROCCO • 2 specs (formalin); same collection data as for holotype; NHMUK 2020.1515 • 2 specs (slide preparation), 1 spec. (ethanol);same collection data as for holotype; DBUA0002294.02 (paragenophores).

Other material

MOROCCO • 3 specs (formalin); same locality as for holotype; 19 May 2009; Stn B09-14b_01W; wood substrata; DBUA0002295.01.

Additional material

SPAIN • 4 specs; Bay of Biscay, Cantabrian Sea; 43°22.18′ – 43°23.14′ N, 02°15.00′ – 02°15.21′ W; 93–101 m depth; 22 Jun. 1991; cruise Fauna II; Stn 150A; MNCN 16.9/13680.

Description

Relatively small specimens compared to most Ophryotrocha species, with proportionally long chaetae. Larger specimens measure from approximately 0.70 to 0.99 mm long and 0.12 mm wide, for 12 to 17 chaetigers (Fig. 3). Prostomium broadly rounded (Fig. 10A), without eyes. Antennae small, spherical, inserted dorsally in mid prostomium; palps bi-articulated with spherical palpophores and ovoid palpostyles, inserted laterally on the posterior part of prostomium (Fig. 10A). Peristomium achaetous, with two rings of similar length to the following segments; anterior ring apparently fused to prostomium. Jaw apparatus light brown, almost inconspicuous (Fig. 10A). Mandibles rod-like, weakly sclerotinized, with curved, serrated cutting edge (with 14 teeth) and large, wing-like apophyses confined to the anterior part of the mandibulae, giving a butterfly-like appearance (Fig. 10C). Maxillae with falcate forceps with a large subdistal tooth below the main fang and transversal ridges posteriorly, giving a wrinkled appearance (Fig. 10 D–E), basely fused to the maxillary carrier; approximately seven free denticles (D1–7) very weakly sclerotized and difficult to examine (Fig. 10D); D1 elongated and lightly serrated, parallel to forceps, D2–7 apparently small and compacted above the forceps (Fig. 10E); the small size of the specimen and the poor sclerotization makes it impossible to count the exact number of free denticles and to observe their morphology more thoroughly. Parapodia long, uniramous, with conical acicular lobes, inconspicuous pre-chaetal lamellae, long sub-acicular lobes and conical dorsal cirri inserted subdistally on the parapodia (Fig. 10H). Anterior parapodia (chaetigers 1–3 or 1–4) with a single compound chaeta (similar to the sub-acicular chaetae) protruding from the sub-acicular lobe (Fig. 10H); following parapodia with simple chaetae protruding from the sub-acicular lobe (Fig. 10I). Supra-acicular chaetae simple, slightly curved sub-distally, coarsely serrated, 2–3 per fascicle (Fig. 10G). Sub-acicular chaetae compound with lightly serrated blades, all of subequal length; shafts distally serrated (Fig. 10F), 3 per fascicle. Pygidium with terminal anus and two clavate anal cirri (Fig. 10 A–B).

Remarks

Ophryotrocha nunezi sp. nov. can be distinguished from all other species by the combination of four characteristics: bi-articulated palps, winged mandibulae, falcate maxillary forceps with internal tooth, and clavate anal cirri. According to the phylogenetic analysis (Fig. 2), six described species of Ophryotrocha and one of Exallopus are placed in the same clade as O. nunezi sp. nov.: O. longidentata Josefson, 1975, O. nauarchus Wiklund et al., 2012, O. magnadentata Wiklund et al., 2012, O. longicollaris Wiklund et al., 2012, O. globopalpata Blake & Hilbig, 1990, O. flabella Wiklund et al., 2012 and E. jumarsi Blake, 1985 (Josefson 1975; Blake 1985; Blake & Hilbig 1990; Wiklund et al. 2012). All these species of Ophryotrocha have bi-articulated palps, but, unlike the others, O. longicollaris does not have winged mandibulae. Furthermore, of all of them, only O. flabella has toothed K-type forceps and only O. magnadentata has clavate anal cirri. The latter species also has sub-acicular lobes sustained by a compound falciger similarly to O. nunezi sp. nov. However, all the other characteristics of both species are different. There are two more species of Ophryotrocha with bi-articulated palps and winged mandibulae (not included in the phylogenetic analysis), O. paragerlachi Brito & Nuñez, 2003 and O. platykephale Blake, 1985, but both these species have long cirriform anal cirri and different parapodial and chaetal morphology (Blake 1985; Brito & Nuñez 2003). Two other species, O. mammillata Ravara, Marçal, Wilund & Hilário, 2015 and O. wubaolingi Miura, 1997, have bi-articulated palps but different mandibulae and anal cirri as well as other morphological features (Miura 1997; Ravara et al. 2015). Ophryotrocha labidion Hilbig & Blake, 1991, from the US Atlantic coast, have bi-articulated palps, winged mandibulae and clavate anal cirri, but strongly differs in the maxillary, parapodial and chaetal morphology (Hilbig & Blake 1991). Another species from the West Atlantic coast, O. atlantica Hilbig & Blake, 1991, with winged mandibulae, falcate forceps with teeth and clavate anal cirri, have simple palps and different maxillary and chaetal morphology (Hilbig & Blake 1991). Paxton & Morineaux (2009) gave a brief description of an undetermined species (Ophryotrocha sp.) reported from the Mid-Atlantic Ridge (Menez Gwen vent field, 865 m depth), that although larger in size, had a similar appearance to this species but with simple palps and mandibulae with a smooth cutting edge. The genus Exallopus also includes species with bi-articulated palps, although this is not the case for the species E. jumarsi, which further differs from O. nunezi sp. nov. by having the antennae weakly annulated, the P-type maxillae and by the presence of strongly modified chaetae in the first chaetigerous segment. This latter characteristic is the main morphological difference between the genera Exallopus and Ophryotrocha. Nevertheless, based on the molecular analyses done to date, the two genera cannot be separated at the molecular level (Fig. 2; Wiklund et al. 2012). The lack of molecular data for the type species of the genus Exallopus (Exallopus cropion Jumars, 1974) has prevented concluding the synonymy of the two genera. Four other non-described species (Ophryotrocha ‘Seep 3, 4 and 5’ and Exallopus ‘seep’, Fig. 2) are placed in the same clade as O. nunezi sp. nov., but no morphological descriptions are available for comparison.

When examining the material of O. cantabrica deposited in the MNCN, Madrid, a vial with additional material was found under the collection number MNCN 16.9/13680 (see Nuñez et al 2014), containing four specimens of the new species described here. It was not possible to perform molecular analyses with this material. Nevertheless, all the morphological characteristics are the same as the specimens from the GoC.

Ecology and distribution

NE Atlantic: from the Cantabrian Sea (Bay of Biscay) to the Gulf of Cadiz (Moroccan Margin). Found in sandy sediments with shells and experimentally deployed wood substrata, at 93–354 m depth.