Ophryotrocha cantabrica Nunez, Riera & Maggio 2014

Ophryotrocha cantabrica Nuñez, Riera & Maggio, 2014

Figs 4–5

Ophryotrocha cantabrica Nuñez, Riera & Maggio, 2014: 116, figs 1–3 (type locality: Gijón (Asturias), Bay of Biscay, Cantabrian Sea, NE Atlantic, 72–74 m depth).

Holotype SPAIN • Bay of Biscay, Cantabrian Sea; 43°37.71′ – 43°38.36′ N, 05°37.59′ – 05°39.78′ W; 72–74 m depth; 15 Jun. 1991; cruise Fauna II; Stn 114A; MNCN 16.0/14704.

Paratypes SPAIN • 38 specs; same collection data as for holotype; MNCN 16.01/13633.

Other material

MOROCCO • 27 specs (ethanol), 44 specs (formalin), 1 spec. (slide preparation); GoC, Mercator MV; 35°17.916′ N, 06°38.709′ W; 354 m depth; 2 Mar. 2008; Stn 64PE284_12750W; wood substrata; DBUA0002281.01 • 7 specs (ethanol), 2 specs (formalin); same collection data as for preceding; 19 May 2009; Stn B09-14b_01W; wood substrata; DBUA0002282.01 • 1 spec. (ethanol), 3 specs (formalin); GoC, Meknès MV; 34°59.091′ N, 07°04.424′ W; 698 m depth; 20 May 2009; Stn B09-14b_03W; wood substrata; DBUA0002282.02.

PORTUGAL • 135 specs (ethanol); WIM, Estremadura Spur; 39°17.295′ N, 10°01.045′ W; 327 m depth; 1 Jun. 2017; Stn PES-ROVL17D01_pick#3W; sunken wood; DBUA0002283.01 (2 hologenophores and 133 paragenophores).

Relatively large specimens in comparison to the majority of the species of Ophryotrocha (Fig. 3). Largest complete specimen 5.4 mm long and 0.8 mm wide for 35 chaetigers. Body compressed dorsoventrally, wider sub-anteriorly and tapering posteriorly (Fig. 4A). A transversal band of cilia present in the middle of each segment. Prostomium broadly rounded, without eyes. Antennae and palps digitiform, sometimes retracted and with a more globulous appearance, subequal in length. Peristomium achaetous, with two rings subequal in length to the following segments. Mouth opens ventrally on the first peristomial ring (Fig. 4B). Mandibles rod-like; cutting plates straight and toothed; apophyses triangular, extending laterally right beneath the tip of the mandibula (Fig. 4B, D). Maxillae of P-type with a pair of forceps and seven pairs of free denticles (D1–7) (Fig. 4E); forceps and D1 comb-like with 13 large teeth alternating with two small teeth; D2–3 shovel-like, with long distal fang and serrated edge; D4–6 with coarsely serrated edge (~11 teeth); D7 shovel-like, broader than the others and with smaller and more numerous teeth (~40). Parapodia uniramous, with broadly conical acicular lobes, long digitiform pre-chaetal lamellae (in median parapodia), conical sub-acicular lobes slightly shorter than pre-chaetal lamellae, conical ventral cirri shorter than sub-acicular lobes, and ovoid to piriform dorsal cirri as long as pre-chaetal lamellae in anterior parapodia and greatly increasing in size posteriorly (Fig. 4A). Protruding acicula of sub-acicular lobes very thin and short. Supra-acicular chaetae simple, serrated, tapering distally to a thin pointed hook (Fig. 4F). Sub-acicular chaetae compound with serrated bidentate blades; secondary tooth tiny and difficult to see (Fig. 4G). Pygidium with terminal anus, two cirriform anal cirri inserted laterally and one short median cirrus (Fig. 4C).

Ophryotrocha cantabrica was originally described from the Cantabrian Sea at 72–74 m depth (Nuñez et al. 2014. The holotype and paratypes were examined during this study and found to be similar in size (Fig. 3) and morphology to the material from GoC and WIM. Only the sub-acicular chaetae of the GoC and WIM specimens seem to have somewhat thicker and shorter blades (Fig. 5D) but this was not considered significant enough to establish a different species. Nuñez et al. (2014) described and illustrated the mandibulae of this species as being distally slightly bifid without serration on the anterior edge. However, a thorough examination of all the specimens (including type material) revealed that the mandibles are often broken at the tip (Fig. 5A), giving the appearance illustrated in the original description (Nuñez et al. 2014: fig. 3a). In fact, when not broken, the mandibles present a ridge of small teeth on its distal edge (Fig. 4D). Also in the forceps and denticle 1 of the maxillary apparatus, the large teeth were found to alternate with two small teeth (Figs 4E, 5B). The phylogenetic analysis segregates this species from the others within the tree (Fig. 2), but there are no DNA sequences from the type material to compare with. The two sequenced specimens were from WIM, the K2P value from the H3 alignment between the two specimens is 0.00 and the K2P value to the nearest species in the tree, O. batillus Wiklund et al., 2012, is 0.10. This study extends the geographic and bathymetric distribution of O. cantabrica to WIM and GoC, where it was the most abundant species, and to a depth of 698 m. It is noteworthy that all our specimens were associated with wood samples only and not with alfalfa grass.

NE Atlantic: from the Cantabrian Sea (Bay of Biscay) to the Gulf of Cadiz (Moroccan Margin). Found in muddy sand, 72–74 m depth, in the Cantabrian Sea (Nuñez et al. 2014), and in wood substrata, 327–698 m depth, at the West Iberian Margin and Gulf of Cadiz (present study).