Ophryotrocha chemecoli, 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 : 54-56

Ophryotrocha chemecoli sp. nov.

urn:lsid:zoobank.org:act:4D7F8D13-207F-4E6F-A364-7F470A042F3D

Fig. 6

Etymology

The species name is an allusion to the colonization devices (CHEMECOLI) deployed in the GoC within the scope of the project CHEMECO (“Monitoring colonization processes in chemosynthetic ecosystems”). This species occurred in five of those devices containing wood and alfalfa, at all three mud volcanoes where the experiment was carried out. CHEMECOLI stands for “CHEMosynthetic Ecosystem COlonization by Larval Invertebrates”.

Material examined

Holotype MOROCCO • complete spec. (ethanol), 1.25 mm long, 0.24 mm wide, 18 chaetigers; GoC, Mercator MV; 35°17.916′ N, 06°38.709′ W; 354 m depth; 2 Mar. 2008; Stn 64PE284_12750W; wood substratum; NHMUK 2020.1510 .

Paratypes MOROCCO • 6 specs (ethanol); same collection data as for holotype; NHMUK 2020.1511 • 12 specs (ethanol), 38 specs (plus 3 cf.) (formalin), 2 specs (slide preparation); same collection data as for holotype; DBUA0002290.01 .

Other material

MOROCCO • 1spec. (formalin); same locality as for holotype; 3Mar. 2008;Stn 64PE284_12752A; alfalfa substrata; DBUA0002290.02 • 1 spec. (formalin); same locality as for holotype; 19 May 2009; Stn B09- 14b_01W; wood substrata; DBUA0002291.01 • 1 spec. (ethanol); GoC, Meknès MV; 34°59.091′ N, 07°04.424′ W; 698 m depth; 20 May 2009; Stn B09-14b_03W; wood substrata; DBUA0002291.02 • 1 spec. (ethanol), voucher DNA, exhausted; GoC, Darwin MV; 35°23.523′ N, 07°11.513′ W; 1100 m depth; 19 May 2009; Stn B09-14b_02A; alfalfa substrata; DBUA0002291.03 .

PORTUGAL • 6 specs (ethanol), 1 spec. (slide preparation); WIM, Estremadura Spur; 39°17.295′ N, 10°01.045′ W; 327 m depth; 1 Jun. 2017; Stn PES-ROVL17D01_pick#3W; wood substrata; DBUA0002289.01 (hologenophore) .

Description

Relatively small specimens, 0.64–1.49 mm long and 0.16–0.26 mm wide for 10–19 chaetigers ( Fig. 3 ). Body dorso-ventrally flattened, with the same width in the anterior half, gradually tapering posteriorly ( Fig. 6A ). Prostomium short and broadly rounded with a flattened anterior rim, without eyes ( Fig. 6A ). Antennae and palps long, digitiform; antennae inserted mid-dorsally on the prostomium; palps inserted laterally. Peristomium achaetous, with two short rings. Jaw apparatus heavily sclerotized, well visible through the specimen body ( Fig. 6 A–B). Mandibles rod-like, with straight and clearly dentate anterior edge; apophyse long, slightly surpassing the cutting edge, narrow and curved laterally ( Fig. 6C ). Maxillae of P-type ( Fig. 6D ); forceps falcate, comb-like with about 13 teeth, wider with thicker teeth on the right side and narrower with thinner teeth on the left side; eleven pairs of free denticles (D1–11), D1 similar to forceps with thick teeth on both sides, D2 and D3 broad, shovel-like, D4 to D11 shovel-like, narrower, usually directed inwards giving a rhomboid appearance to the maxillae; carrier-like structure with a toothed ridge on each side near the forceps, posterior end with a fimbriate handle. Parapodia uniramous ( Fig. 6E ); pre-chaetal lamellae of the median parapodia long, conical; dorsal and ventral cirri conical (dorsal longer than ventral); sub-acicular lobes conical, similar in size to pre-chaetal lamellae, with a short, needle-like acicula protruding. Chaetae long and stiff; supra-acicular chaetae simple, slightly flattening and tapering distally to a fine tip, very lightly serrated ( Fig. 6F ); sub-acicular chaetae compound, with bifurcate, sub-distally serrated shafts and falcate, very lightly serrated blades ( Fig. 6G ). Pygidium with terminal anus, a pair of cirriform anal cirri and a very short, rounded median stylet.

Remarks

Ophryotrocha chemecoli sp. nov. is very close at molecular ( Fig. 2 ) and morphological levels to the species O. scutellus Wiklund, Glover & Dahlgren, 2009 , O. lusa Ravara, Marçal, Wiklund & Hilário, 2015 and O. batillus Wiklund et al., 2012 . Ophryotrocha scutellus and O. lusa are known to occur in the NE Atlantic ( Wiklund et al. 2009; Ravara et al. 2015), whereas O. batillus occurs in the NE Pacific ( Wiklund et al. 2012). Like O. chemecoli sp. nov., all of those species have a dorso-ventrally flattened body, a long parapodial pre-chaetal lobe and roughly rhombus-shaped maxillae. Also the chaetae of O. scutellus and O. batillus are very similar to those of the new species. However, O. scutellus differs from O. chemecoli sp. nov. by the larger body size, the flatter prostomium, the much longer pre-chaetal lobe and the mandibular morphology of the adult specimens; whereas O. batillus differs in the very large size of the parapodia and chaetae, the flatter and wider prostomium and, to some extent, also the mandibular shape. As in O. chemecoli sp. nov., O. lusa has eleven pairs of maxillary free denticles, while the other Ophryotrocha species usually have only eight or less ( Paxton 2004, 2009; Ravara et al. 2015). Furthermore, the size of the specimens of the new species, as well as the neurochaetae and the mandibulae shape, are similar to those of younger specimens of O. lusa , making it difficult to distinguish between the two species. The adult specimens of O. lusa , however, have very different neurochaetae and mandibular morphology (see Ravara et al. 2015). Such variation in the mandibular morphology was not observed in the specimens of O. chemecoli sp. nov., although globular masses, indicating reproductive maturity, were detected at the base of median parapodia of some larger specimens. In the phylogenetic analysis, O. cantabrica also groups in the same clade as O. chemecoli sp. nov. ( Fig. 2 ). At the morphological level, these species are very different, having only the morphology of the chaetae in common.

Ecology and distribution

NE Atlantic: from the Estremadura Spur (West Iberian Margin) to the Gulf of Cadiz (Moroccan Margin). Found in wood and alfalfa substrata at 327–1100 m depth.

Figures

Fig. 6. Ophryotrocha chemecoli sp. nov. Stereo (A–B) and compound (C–G) microscope images. A–B: NHMUK 2020.1510; C–D, F–G: DBUA0002290.01; E: DBUA0002289.01.V01 (hologenophore). A. Holotype, entire specimen, dorsal view.B. Holotype, anterior end, ventral view.C. Mandibulae, ventral view. D. Maxillae, dorsal view. E. Mid-body parapodium, posterior view. F. Supra-acicular chaeta, midbody parapodium. G. Sub-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.