Ophryotrocha cyclops Salvo, Wiklund, Dufour, Hamoutene, Pohle & Worsaae, 2014, sp. nov.

Ophryotrocha cyclops, sp. nov.

Figs 1, 2

Material examined. Type material: Holotype, Fortune Bay, Newfoundland, Canada, site A, 47˚38’40”N, 55˚14’15”W, beneath salmon cages, 55 m depth, net sampling, October 2012, collector F. Salvo, preserved in 95% ethanol, deposited at the Canadian Museum of Nature (CMN), accession number CMNA 2014-0002; three paratypes, same location and collector, October 2012, preserved in 95% EtOH (accession numbers: CMNA 2014- 0003– CMNA 2014-0005); four paratypes, Fortune Bay, Newfoundland, Canada, site B, 47°37’24”N, 55˚49’24”W, beneath salmon cages, 72 m depth, November 2012, collector F. Salvo, preserved in 95% EtOH (accession numbers: CMNA 2014-0006– CMNA 2014-0009); five DNA voucher specimens, same locations (2 from site A and 3 from site B), date and collector, preserved in 95% ethanol (accession numbers, site A: H1: CMNA 2014- 0 0 10, H4: CMNA 2014-0011; site B: H7: CMNA 2014-0012, H8: CMNA 2014-0013, H12: CMNA 2014- 0014; CMN); DNA voucher specimens, Malene Bay, Nuuk, Greenland, 64°9’25”N, 51°41’49”W, collected on whalebones, 123 m depth, October 2009, preserved in 95% ethanol (deposited at the Natural History Museum in London (NMH), UK) under accession numbers: H9: NMH2014.84, H10: NMH2014.85, H11: NMH2014.86) and Fortune Bay, Newfoundland, Canada, site C, 47º44’58”N, 55º 59’57”W, beneath trout cages, April 2010, collector D. Ings, preserved in 95% ethanol (accession numbers: H2: NMH2014.80, H3: NMH2014.81, H5: NMH2014.82; H6: NMH2014.83; NMH). Paratypes of O. cyclops sp. nov. have been also deposited at the Atlantic Reference Centre of the Huntsman Marine Science Centre under catalog numbers 77495, 77496, 79207 and 79208.

Description. The preserved specimens range from 1.4 to 12 mm in length; Fig. 1 B shows a specimen with 37 chaetigers, measuring 7.5 mm. Colour pale red or transparent (becoming opaque white in fixative) with large lateral subtriangular lobes, located dorsally and ventrally to parapodia (Fig. 1 A–C; 2A). Body shape elongated, uniformly wide from the anterior to the middle of the body, then tapering slightly at toward posterior end. Body dorsally rounded, with shallow central depression ventrally, the latter being more pronounced in fixed specimens. Prostomium with digitiform paired antennae inserted dorsally (Fig. 1 A). Palps biarticulated with large palpophores and small papilliform palpostyles, inserted laterally on prostomium (Fig. 1 C). A pair of light-reflecting eyes connected with a strand visible on live animals; reflecting incident light as single yellowish white spot (Fig. 1 C). Jaws of K– type and P– type, mandibles L–shaped with serration anteriorly consisting of 13–16 teeth, narrow medially and becoming basally broader toward the edges of the mandibles (Fig. 1 D–E). Maxillae with 7 free denticles (Fig. 1 D–F). K-type forceps smooth, denticles attached to forceps with ligament (Fig. 1 D). P-type forceps with two transverse ridges with alternating large and small teeth, and with a fang distally. (Fig. 1 E). Maxillae in both jaw types having alternating large and small teeth, and a fang distally (Fig. 1 D–F).

Two peristomial achaetous segments similar in size to chaetigerous segments. Parapodia uniramous with long dorsal and ventral cirri and cirriform acicular lobe, supra-acicular chaetae simple with fine serration; subacicular chaetae compound, with very finely serrated blades (Fig. 2 A–C). Retractable subacicular chaetal lobe with simple chaetae (Fig. 2 A, D). Pygidium with terminal anus and two short pygidial cirri, unpaired appendage absent.

Distribution. Known from rocky bottom and on the top layer of flocculent matter beneath fish farms at 30–73 m depth on the south coast of Newfoundland and on whalebones at 123 m depth in Malene Bay, Nuuk, Greenland.

Etymology. Ophryotrocha cyclops in reference to the appearance of a single dorsal eye.

Remarks. This species is similar to Ophryotrocha craigsmithi Wiklund et al., 2012, O. lipovskyae (Paxton, 2009), O. lobifera Oug, 1978, O. orensanzi Taboada et al., 2013, O. platykephale Blake, 1985, O. shieldsi Paxton & Davey, 2010, and O. wubaolingi Miura, 1997 in having lobe-like structures both dorsally and ventrally, biarticulated palps, and L-shaped mandibles. It differs from O. platykephale in the form of the prostomium and parapodia, and from O. orensanzi and O. wubaolingi in the shape of the parapodia. It differs from O. shieldsi, O. craigsmithi and O. lipovskyae in the form of the dorsal lobes, which are triangular in the new species, but ovate in O. shieldsi and rounded in the other two. It is morphologically most similar to O. lobifera which occurs further east in the north Atlantic, along the coasts of Norway and Sweden. In the description of O. lobifera, the denticles are described as having only small dorsal teeth (Oug 1978), while the new species have alternating large and small teeth. Furthermore, the mandibles in O. lobifera are reported to have large medial teeth in combination with 14–18 smaller teeth anteriorly, while the new species has medial teeth no larger than the other teeth anteriorly on the mandibles. Due to this and the genetic differences (see ‘Phylogenetic analysis’ below) we describe the sampled worms as a new species from the northwest Atlantic, and propose that jaw morphology and geographic location, preferably combined with genetic information, be used to separate the two species.

Laboratory observations. Specimens from sites A and B in Newfoundland were kept in the dark at 4°C for several months without adding any food. When observed under the dissecting microscope, a few individuals released yellow eggs (size not measured) from different regions along the length of their body, before they died (perhaps due to heat stress). Only two specimens were observed under SEM and no rosette glands were observed.

The worms observed alive on the whalebone from Greenland moved in and out of the porous surface and seemed to feed directly on the flocculent, decomposed bone and the bacterial mats that covered them.

Phylogenetic analysis. The combined dataset consists of 1513 characters, with 539 contributed by the 16S alignment, 629 by COI, and 345 by H3. According to both the Bayesian tree model combining three genes (Fig. 3) and the haplotype network (Fig. 4), the Greenland and Newfoundland specimens form a single species of the dorvilleid genus Ophryotrocha. There is strong support for O. cyclops falling within the 'lobifera' clade (Fig. 3). Within that clade, it is most closely related to O. craigsmithi (probability of 64%), followed by O. lobifera and O. shieldsi, with strong support for clustering of those four species (up to 95%) (Fig. 3). All sequences obtained are deposited in GenBank (Table 2).

The haplotype network analysis using COI included twelve haplotypes of the new species together with sequences from Ophryotrocha craigsmithi and O. lobifera to investigate the relationships between the morphologically similar species, as well as the distribution pattern of the new species from the three different localities. Each of the haplotypes 1, 10 and 11 consists of two individuals, while the other haplotypes consist of a single individual. The results show that haplotypes from Newfoundland (sites A, B and C) are close to each other (within 3 steps difference), with the exception of one haplotype from site B that is more closely related to haplotypes from Greenland than to other haplotypes from the same collection site (Fig. 4). The former group is separated in the haplotype network from the Newfoundland group by about 10 steps, whereas they differed from O. craigsmithi by up to 101 steps, and from O. lobifera by 89 steps. Uncorrected 'p' distances in COI show a maximum distance of 0.025 within the new species, and the minimum distance to O. lobifera is 0.149, while the minimum distance to O. craigsmithi is 0.17. The distance between O. lobifera and O. craigsmithi is 0.18. Uncorrected 'p' distance between the new species and O. lobifera is 0.059 in 16S and 0.079 in H3, and between the new species and O. craigsmithi it is 0.053 in 16S and 0.062 in H3.