Ophryotrocha rubra Paxton & Åkesson, 2010, sp. nov.

Ophryotrocha rubra sp. nov.

Figure 1 E; Table 1

Ophryotrocha rubra nom. nud. Pleijel & Eide, 1996; Heggøy et al. 2007; Wiklund et al. 2009.

Material examined. Type material: Holotype (AM W36881), complete female specimen, 2.6 mm long, 0.40 mm wide without parapodia (preserved) for 19 chaetigers; allotype (AM W36882) complete male specimen, 1.3 mm long, 0.25 mm wide without parapodia (preserved) for 14 chaetigers; 10 paratypes (AM W36883); 10 paratypes (SMNH T- 8033); cultured from specimens collected at Ceuta, Spain in 1978. Other material: Live cultures from same collection.

Description. Length of most live adults 2–3 mm (12–14 chaetigers), maximum length 4 mm (20 chaetigers). Live animals (Fig. 1 E) translucent, preserved opaque white. Pigmentation consisting of very small red spots on most chaetigers, when best developed in large animals, forming rows of spots on some segments (Fig. 1 E). Prostomium anteriorly rounded; with pair of short ovate antennae; palps absent; two distinct eyes, not medially connected. Two peristomial achaetous segment-like rings.

Parapodia uniramous, lacking dorsal and ventral cirri, with dorsal protrusion, with retractile ventral lobe; 2–3 supra-acicular simple chaetae, 2–4 subacicular heterogomph falcigers and inferiormost simple chaeta; distal part of simple chaetae and blades of falcigers coarsely serrated. Pair of pygidial cirri present, pygidial median stylus absent in adults. Rosette glands, one per segment, present mid-dorsally on posteriormost segments of mature animals, up to five to six in males and females.

Mandibles with elongate shafts and bifid cutting plates with 18–21 tiny pointed teeth at anterior edge. Maxillary apparatus of P- and K-type in both sexes, with falcate P1-forceps, bidentate P2-forceps, K-forceps right bidentate, left falcate.

Reproduction and development. Gonochoristic; chromosomes 2n = 10. diameter of eggs 165–170 µm; tubular egg masses; released larvae with two chaetigers, with short pygidial median stylus.

Etymology. The name of the new species refers to its numerous red spots.

Remarks. The new species was originally identified through crossbreeding experiments and has been confirmed by gene sequence studies (Heggøy et al. 2007; Wiklund et al. 2009). Ophryotrocha rubra is most closely related to O. robusta, the only other species in the O. labronica group with a diploid chromosome complement of 10. Both species have separate eyes but differ in their reproductive characteristics in that O. rubra has large eggs that develop into 2-chaetiger larvae before leaving the egg mass, while O. robusta has small eggs that leave as 0-chaetiger larvae.

Distribution. Mediterranean/Strait of Gibraltar: Tarifa, Ceuta, Spain.