Metavermilia zibrowii Bailey-Brock & Magalhães, 2012, sp. nov.

Metavermilia zibrowii sp. nov.

Figures 1 (A– O), 2 (A and B) and 3 (A–F)

Material examined. Holotype: Cross Seamount, Hawaii, “Moana Wave” cruise leg 13, dredge haul 2, 18 °47.52’N 158°13.73’W, HURL, 12/16/1981, 2,013 m (USNM 1156950); Paratype: same location and date as holotype (1, BPBM R3557).

Description. TUBE: Rugged white tubes with broad lateral flanges and ascending mouth in one specimen (Figs 1 A; 2A), terminating with a thin flared lip. Four or five uneven longitudinal ridges present, not forming teeth, with narrow transverse ridges between them (Figs 1 B, C; 2A). Tubes measured about 25 mm in length and 2–3 mm in width. One specimen removed from the tube measures 13 mm in length, excluding branchial crown.

BRANCHIAE: Branchial crown with 12–13 radioles on either side; the second (modified) radiole on left or right side bearing the operculum.

PEDUNCLE: Opercular peduncle flat and wrinkled (Figs 1 D, E; 2B).

OPERCULUM: Operculum composed of a funnel-shaped ampulla with chitinous concave opercular plate, brown to yellow in color (Figs 1 E; 2B).

COLLAR and thoracic membranes: collar trilobed; thoracic membrane extending to between chaetigers 6 and 7; apron absent.

THORAX: with collar chaetiger and 6 uncinigerous chaetigers. Collar chaetae limbate and narrowly winged capillaries (Figs 1 F, G; 3A); thoracic chaetae limbate (Fig. 1 H), more numerous than collar chaetae, capillaries (Fig. 1 I) and Apomatus chaetae with a small limbate zone from chaetiger 3 (Fig. 3 A shows basal part of Apomatus chaeta in Fig. 1 J and Fig. 3 B showing distal part of same Apomatus chaeta). Thoracic uncini saw-shaped with up to 11 teeth including rounded anterior fang (Figs 1 K; 3C).

ABDOMEN: composed of about 80 chaetigers, with two kinds of chaetae and uncini. Abdominal chaetae with flat narrow geniculate blade (Fig. 1 L), 2 per fascicle, except for posterior-most chaetigers with long capillaries (Fig. 1 M; 3D, E). Abdominal uncini saw-shaped in most chaetigers with 8 or 9 teeth including a simple anterior tooth (Fig. 1 N) and rasp-shaped in posterior-most chaetigers (Fig. 1 O) with about 15 rows of teeth, 4–6 teeth per row and a rounded anterior fang. Glandular pad present on last abdominal segments and composed by several rounded structures with calcium carbonate crystals protruding from a shallow pit (Fig. 3 F).

Remarks. The two specimens agree with the generic characters given by Zibrowius (1971), Nishi et al. (2007) and ten Hove & Kupriyanova (2009), where a flat and ribbon-like opercular stalk is present. The new species resembles Metavermilia annobonensis (Augener, 1914) in most cases (e.g. tubes with 4–5 irregular longitudinal ridges and operculum with a concave distal plate), but differs in the number of teeth in the thoracic uncini, 7 according to Zibrowius (1971), 11 (but see Fig. 3 C) in the Hawaiian specimens; thoracic membrane extends to thoracic chaetigers 3–4 according to Zibrowius (1971) and Nishi et al. (2007) for M. annobonensis, but thoracic membrane extends to between chaetigers 6 and 7 in the Hawaiian material.

Other Metavermilia species with simple opercula include M. ogasawarensis Nishi, Kupriyanova & Tachikawa, 2007, M. arctica Kupriyanova, 1993, M. multicristata (Philippi, 1844), M. taenia Zibrowius, 1971, M. nanshaensis Sun, 1998, M. gravitesta Imajima, 1977, M. inflata Imajima, 1977 and M. ovata Imajima, 1978. Opercula of M. ogasawarensis, M. nanshensis and M. arctica are simple conical with flat plates and/or with conical tubercle in the center (Nishi et al., 2007). Metavermilia. inflata is distinct in having a soft globular operculum without distal plate while M. ovata has a distinct ovoid process terminating in two hooks over the thick distal plate. The globular opercula of M. multicristata and M. taenia have a simple horny convex distal cap, not concave as in M. zibrowii sp. nov. Finally, M. gravitesta differs from the new species described herein by the curved horny distal cap on the operculum.

Etymology. The species is named for Dr. Helmut Zibrowius who kindly examined my notes and illustrations (JB-B) of these Hawaiian specimens and offered advice on their diagnosis.

Distribution. Cross Seamount in the Hawaiian Chain, 2,013 m.