Diopatra mellea Paxton & Arias 2017, sp. nov.

Diopatra mellea sp. nov.

Figures 13–15; Table 1, 2

Material examined. Type material. Holotype: MNCN 16.01 /17821, La Laja beach, Gran Canaria, Canary Islands, 28°03’N – 15°25’W, intertidal, coll. A. Arias, 12 Aug 2012; paratype: AM W.49216 same data as holotype.

Type locality. Eastern North Atlantic, Canary Islands, Gran Canaria, Las Palmas, La Laja beach, 28°03’N – 15°25’W, intertidal.

Diagnosis. Prostomium anteriorly rounded with two subulate frontal lips; antennae to chaetiger 6–11 with 12– 13 ceratophoral rings, lateral projections absent; nuchal grooves crescentic to semicircular; peristomial cirri present. Anterior five to six pairs of parapodia with bidentate pseudocompound hooks with falcate hoods; double postchaetal lobes. Ventral parapodial lobes absent, ventral cirri on five chaetigers. Subacicular hooks from chaetiger 19–20; pectinate chaetae with 4–11 teeth; spiralled branchiae, first on chaetiger 5, last single filament on chaetiger 70.

Description. Both types incomplete, holotype 31 mm long for 95 chaetigers, 2.0 mm wide; paratype 28 mm for 70 chaetigers, 3.5 mm wide. Ethanol stored specimens overall very pale brown with some mottled darker brown pigmentation at anterior part of prostomium, ceratostyles, peristomial cirri, first pairs of parapodia, their lobes and cirri; also brown ceratophoral rings and a brown band on anterior edge of first ten segments (Fig. 13 A–C).

Prostomium anteriorly rounded with two closely spaced subulate frontal lips. Ventral upper lips oval with papilla-like median section between lips; lower lip with median section (Fig. 13 B). Palps reaching to chaetiger 4, lateral antennae to chaetiger 7–8 (11), median antenna to chaetiger 6 (10); ceratophores with 12 (11–12) proximal rings and a longer distal ring, ceratostyles tapering to distal end, with fine tips. Styles with about 20–22 irregular longitudinal rows of sensory buds (Fig. 14 A); buds slightly raised, forming semi- to almost full circles (Fig. 14 B, C). Nuchal grooves crescentic to semicircular. Peristomial cirri subulate, slightly longer than peristomium, inserted distally on peristomium, below lateral antennae (Fig. 13 A).

First six (five) pairs of parapodia modified, slightly prolonged and directed anteroventrally. Prechaetal lobe rounded; large subulate upper and shorter lower postchaetal lobes. Development of lower lobes variable, ranging from knob-like (Figs 14 D, 15A) to subulate (Fig. 15 B), even on parapodia of same chaetiger. Prechaetal lobe becoming reduced, absent from about chaetiger 20. Upper postchaetal lobe becoming smaller but remaining as little knob into posterior region; lower postchaetal lobe absent from chaetiger 6(5). Dorsal cirri subulate, becoming very slender posteriorly; ventral cirri subulate on anterior five chaetigers, thereafter replaced by ventral glandular pads (Fig. 13 B). Ventral lobe absent. Spiralled branchiae from chaetiger 5, best developed on chaetigers 6–8 (Fig. 13 A–C) with about 15 closely spaced whorls on thick trunk reaching to chaetiger 1 when anteriorly extended. Individual filaments slender, slightly longer than branchial stem wide, number of filaments decreasing gradually after chaetiger 10 (Fig. 14 E, F); single filaments from chaetiger 70, absent shortly thereafter.

Modified parapodia (chaetigers 1 to 6 or 1 to 5) with one to two slender upper simple limbate chaetae and pseudocompound bidentate hooks with falcate hoods and almost smooth shafts (Fig. 14 G). Each parapodium with one median robust hook (Fig. 15 C) and two to three more slender ones (Fig. 15 D) from main pocket, and two to three very slender hooks (Fig. 15 E) from lower position.

Unmodified parapodia (chaetigers 7 or 6 onwards) with pectinate and limbate chaetae (Fig. 14 E, F). Pectinate chaetae slightly oblique with 4–11 teeth (Figs 14 H, 15F, G), two to five in median body region. Limbate chaetae finely serrated by chaetiger 30–40; lower limbate chaetae replaced by bidentate subacicular hooks from chaetiger 19 (19–20).

Mandibular shafts short in relation to size of maxillae (Fig. 15 H), calcareous part of cutting plates dissolved. Maxillae (Fig. 15 I) slender, maxillary formula: Mx I = 1 + 1; Mx II = 9 + 8; Mx III = 7 + 0; Mx IV = 7 + 10; Mx V = 1 + 1. Tubes consisting of inner secreted layer, overlain by further mucous secretions to which small pebbles and shell pieces are attached (Fig. 13 D).

Etymology. The name is derived from mel (honey) in Latin and refers to the worm’s honey-coloured appearance.

Remarks. The affinities of D. mellea sp. nov. have been discussed above (see Remarks to D. mariae sp. nov.).

Distribution. Diopatra mellea sp. nov. is only known from Gran Canaria, Canary Islands.