Ophryotrocha geoffreadi, Ravara, Ascensão, Wiklund, Helena & Cunha, Marina R., 2021

Ravara, Ascensão, Wiklund, Helena & Cunha, Marina R., 2021, Four new species and further records of Dorvilleidae (Annelida, Polychaeta) from deep-sea organic substrata, NE Atlantic, European Journal of Taxonomy 736, pp. 44-81 : 56-59

Ophryotrocha geoffreadi sp. nov.

urn:lsid:zoobank.org:act:F5023AAF-791B-47A3-90A2-824D50CC4826

Fig. 7

Etymology

The species is named after Dr Geoffrey Read, the chief taxonomic editor of Polychaeta at the World Register of Marine species (WoRMS) and founder of the Annelida mailing list. His tireless work in both these initiatives is an immense and invaluable aid to all polychaetologists.

Material examined

Holotype MOROCCO • complete spec. (ethanol), 0.94 mm long, 0.17 mm wide, 16 chaetigers; GoC, Meknès MV; 34°59.091′ N, 07°04.424′ W; 698 m depth; 20 May 2009; Stn B09-14b_03W; wood substrata; NHMUK 2020.1512 .

Paratypes MOROCCO • 31 specs (formalin); same collection data as for holotype; NHMUK 2020.1513 • 1 spec. (ethanol), 2 specs (slide preparation); same collection data as for holotype; DBUA0002286.02 .

Other material

MOROCCO • 5 specs (ethanol); same locality as for holotype; 20 May 2009; Stn B09-14b_03A; alfalfa substrata; DBUA0002286.03 (1 hologenophore, 4 paragenophores) • 2 specs (ethanol), 13 specs (formalin); GoC Darwin MV; 35°23.523′ N, 07°11.513′ W; 1100 m depth; 19 May 2009; Stn B09- 14b_02A; alfalfa substrata; DBUA0002286.04 • 9 specs (ethanol), 1 spec. (slide preparation), 5 specs (formalin); same collection data as for preceding; 19 May 2009; Stn B09-14b_02W; wood substrata; DBUA0002286.05 .

Description

Relatively small specimens compared to most species of Ophryotrocha . Most of the larger specimens are damaged or incomplete and were not measured. Measured specimens 0.73 to 1.46 mm long and 0.19 mm wide, for 17 to 25 chaetigers ( Fig. 3 ). Body dorso-ventrally flattened, wider anteriorly and tapering posteriorly. Prostomium broadly rounded ( Fig. 7A ), without eyes. Antennae and palps short, cirriform; antennae inserted mid-dorsally on the prostomium; palps inserted laterally. Peristomium achaetous, with two rings of length similar to the following segments. Jaw apparatus brown, well visible through the specimen body. Mandibles rod-like, with straight, serrated cutting edge (with around 8 teeth in smaller specimens, Fig. 7B ) and weakly sclerotized apophyses, shorter than cutting edges. In larger specimens, the cutting edge teeth are usually worn and the apohyses are enlarged longitudinally ( Fig. 7E ). Maxillae of P-type (also after moulting) with asymmetric forceps; left forceps narrow and finely toothed (up to 35? teeth), right forceps wider and coarsely toothed (~15 teeth) ( Fig. 7F ); seven free denticles (D1–7; Fig. 7C, F ), D1 comb-like coarsely toothed, similar to right forceps, D2 shovellike with an outer larger tooth and coarse teeth, D4–6 shovel-like with smaller teeth slightly increasing in number anteriorly, D7 shovel-like, much broader than the others; carrier-like structure with a toothed ridge on each side at the base of the bifurcation ( Fig. 7F ) and a posteriorly fimbriate handle ( Fig. 7C ). Parapodia uniramous, with conical acicular lobes, inconspicuous pre-chaetal lamellae, long sub-acicular lobes and conical dorsal cirri inserted sub-distally on the parapodia ( Fig. 7D ); ventral cirri absent. Subacicular lobes with a short needle-like protruding acicula ( Fig. 7H ). Chaetae relatively short and stiff; supra-acicular chaetae simple, tapering distally, smooth or very finely serrated, up to 7 per fascicle ( Fig. 7I ); sub-acicular chaetae compound with sub-distally serrated shafts and falcate, lightly serrated blades ( Fig. 7G ), up to 7 per fascicle. Pygidium with terminal anus, a pair of short cirriform anal cirri (spherical and almost inconspicuous in smaller specimens) and a median papilla.

Remarks

According to the phylogenetic analysis ( Fig. 2 ), O. geoffreadi sp. nov. is close to the species O. langstrumpae Wiklund et al., 2012 , O. sadina Ravara, Marçal, Wiklund & Hilário, 2015 , O. cantabrica Nuñez, Riera & Maggio, 2014 , O. scutellus Wiklund, Glover & Dahlgren, 2009 , O. lusa Ravara, Marçal, Wiklund & Hilário, 2015 , O. batillus Wiklund et al., 2012 and O. chemecoli sp. nov. ( Wiklund et al. 2009, 2012; Nuñez et al. 2014; Ravara et al. 2015). However, unlike O. geoffreadi sp. nov., all those species have well-developed parapodial lobes and cirri, and only two of them ( O. langstrumpae and O. cantabrica ) have mandibulae with a straight cutting edge but without membranous apophyses. Three other species that are not included in the phylogenetic analysis have mandibulae with a straight, serrated cutting edge: O. pachysoma Hilbig & Blake, 1991 from the W Atlantic (604–2065 m depth), O. natans Pfannenstiel, 1975 from the Red Sea (intertidal) and O. kagoshimaensis Miura, 1997 from the W Pacific (197 m depth) ( Pfannenstiel 1975; Hilbig & Blake 1991; Miura 1997). Nevertheless, the presence of a membranous apophyse below the cutting edge is not clear for the two latter species, and the cutting edge of the mandibulae of O. pachysoma is much wider and also serrated on its internal border. Furthermore, the maxillary, parapodial and chaetal morphology of all these species is different from that of O. geoffreadi sp. nov.

Ecology and distribution

NE Atlantic: Gulf of Cadiz (Moroccan Margin). Found in experimentally deployed wood and alfalfa substrata, at 698–1100 m depth (this study).

Figures

Fig. 7. Ophryotrocha geoffreadi sp. nov. Stereo (A) and compound (B–I) microscope images. A–D: DBUA0002286.02; E–I: DBUA0002286.05. A. Anterior region, ventral view. B. Mandibulae of a smaller specimen, ventral view. C. Maxillae of the same specimen with moulting pieces, ventral view. D. Median parapodia, anterior view. E. Mandibulae of a larger specimen, ventral view. F. Maxillae of the same specimen, dorsal view. G. Sub-acicular chaetae of mid-body parapodia. H. Simple chaeta protruding from the sub-acicular lobe of a mid-body parapodium. I. Supra-acicular chaetae, mid-body parapodium. Numbers refer to free denticles.

Fig. 3. Relationships between the number of segments, body length and body width.

Fig. 2 (next page). Majority rule consensus tree from the Bayesian analyses of a combined dataset with two genes (16S and H3). Posterior probability values near nodes result from the analyses in MrBayes. Taxon names highlighted in bold are new species or new sequences for already described species. Habitat specialization indicated by the text ‘VENT’ for hydrothermal vents, ‘SEEP’ for cold seeps, ‘BONE’ for whale/mammal-falls, ‘WOOD’ and ‘ALFALFA’ for wood- and alfalfa-falls, and ‘FISHFARM’ for the organically-enriched sediments beneath fish farms. Brown bars at the base of a clade indicate a specialization to a chemosynthesis-based ecosystem. Green and blue dots indicate depth distributions shallower and deeper than 200 m, respectively.