Metavermilia ogasawaraensis, Nishi, Eijiroh, Kupriyanova, Elena & Tachikawa, Hiroyuki, 2007

Nishi, Eijiroh, Kupriyanova, Elena & Tachikawa, Hiroyuki, 2007, Metavermilia ogasawaraensis sp. nov. (Serpulidae: Sabellida: Polychaeta: Annelida) from deep-sea locations off Ogasawara Island, Japan with a literature overview of the genus, Zootaxa 1447, pp. 47-56 : 49-53

Metavermilia ogasawaraensis sp. nov.

( Figs. 1 – 3)

Material examined: East off Mukojima, Ogasawara Islands, attached to a pseudo-colony of Crispatotrochus sp., the deep sea scleractinian coral, KT-97-07 cruise of R/V “ Tansei Maru, Ocean Research Institute, University of Tokyo, Station MK-07, 3m beam trawl, 27° 46’ 55”N, 142° 28’ 77’’E, 1603 m to 27° 47’95”N, 149° 2907E, 1711 m, 7 June, 1997.

CMNH-ZW01700. Holotype with tube. Holotype and 3 paratypes. SAM-E3572. SMF 16603, some parapodia have been dissected for light and scanning electron microscopy examination observations. One copepod parasite attached to the abdomen. NHM-2006.2039, one incomplete specimen without tube.

Description. Holotype, complete, 11.5 mm in length with branchia, 6 mm without branchia, 1 mm width at thorax, 0.5 to 0.8 mm at abdomen; with anterior part of tube ( Fig. 1 A–C). Thorax with 7 chaetigers, of which 6 with uncini (Fig. 2B, C), abdomen with 54 chaetigers. Branchial crown and trunk lack coloration (probably) due to the alcohol preservation, in all specimens. Three paratypes, 2 complete (SAM-E3572 and NHM-2006.2039) and one incomplete (SMF 16603), are lacking posterior parts because dissected off for detailed examination and retained on SEM stab. The first chaetiger of the holotype, stained with methylene green, shows 2 eye-like spots ventrally (Fig. 2A–C); ventral pads deeply stained (Fig. 2B, C). Branchial crown with 15 to 20 radioles, in semi-circular arrangement; radioles not connected by branchial membrane. All radioles end distally in pinnule-free distal tip (Fig. 2D). Second radiole on right side transformed into large, flattened, opercular stalk that is thicker and wider in middle to distal part (Fig. 2J) and thinner and narrower in basal part (Fig. 2K), lacking distal wings (Fig. 2E, F). Operculum consists of proximal soft transparent, semi-spherical or globular part, and white, flat distal plate ( Fig. 1 A, B). Distal plate with small conical pointed tubercle in middle (Fig. 2E, F).

Collar large and divided into ventral semi-triangular lobe and latero- ventral lobes (Fig. 2A, B, C). Thoracic membranes poorly developed, narrow and ending at 4th thoracic chaetiger (Figs. 2A, B, 3A).

Collar chaetae fascicles with limbate chaetae only (Fig. 3B). Chaetae of second chaetiger onwards with capillaries, limbate, and "sickle" chaetae (= Apomatus chaetae) with denticulate blade and limbate proximal zone (Fig. 3C). Thoracic uncini saw-shaped, with 7–9 teeth in one row (Fig. 3D).

FIGURE 2. Metavermilia ogasawaraensis n. sp., holotype. A to C, Anterior part, dorsal (A), lateral (B), and ventral (C) views. D, tip of radiole. E and F, operculum (E, lateral, and F, upper view). G, posterior abdominal segments and anus, ventral view. H and I, tube, lateral view (I) and opening (H). Cross section of opercular stalk, middle part (J) and basal part (K). Scales are 0.5 mm (A–C), 0.25 mm (D–G, J, K), 1 mm (H, I).

FIGURE 3. Scanning electron micrographs of Metavermilia ogasawaraensis n. sp. A. Thorax and chaetae. B. Collar chaetae. C. 4th thoracic chaetae. D. Thoracic uncini. E–F. Abdominal uncini. G. Abdominal chaetigers. H. Abdominal chaeta. I. Abdominal serrated chaeta (distal part). Scales are 500µ m (A), 50µ m (B, C), 10µ m (D, H), 20 µ m (E, I), 5 µ m (F), 200µ m (G).

Abdominal chaetae long, 0.5 mm to 0.8 mm, up to 1.0 mm, longer than abdomen width (0.4 to 0.6 mm, Fig. 3G); not geniculate, with long blade and with denticulate edge in distal part (Fig. 3H, I). Abdominal uncini semi-triangular, rasp-shaped, with 3 – 4 rows, 9 – 10 teeth in lateral view, and with projecting undivided peg (Fig. 3 E, F).

Tube white, lustreless, semi-circular in cross section, with many flaring peristomes, edge irregular, encircling tube ( Figs. 1 C, 2H, I). Tube attached to coral skeleton at base and anterior most parts are raised from the coral substrate.

Remarks. Metavermilia ogasawaraensis n. sp., is characterized by its operculum, chaetae and tube morphology (summarized in Table 1). The simple operculum of M. ogasawaraensis n. sp., is also typical for some species of the genus such as M. annobonensis , M. arctica , M. multicristata , M. taenia , M. nanshaensis , M. gravitesta , M. inflata , and M. ovata ( Fig. 4 ). Out of those species, Metavermilia inflata stands out because of its soft globular operculum without any sign of distal plate ( Fig. 4 N, O), while the operculum of M. ovata is unusual in carrying a distinctive ovoid process terminating with two hooks on thick concave distal plate ( Fig. 4 P, Q). Remaining species of the genus ( M. nates , M. acanthophora , M. spicata , and M. yamazotoi ) have easily recognizable complex multi-tiered opercula ( Fig. 4 ). The conical operculum of M. ogasawaraensis n. sp., with flat distal plate resembles the similar conical opercula of M. annobonensis , M. arctica , and especially M. nanshaensis that also has a conical tubercle in the centre.

Metavermilia ogasawaraensis n. sp., is characterized by poorly developed thoracic membranes that reach to the thoracic chaetiger 4 (Figs. 2A, 3A) as in Metavermilia annobonensis , M. arctica , and M. nanshaensis . Thoracic membranes extend to thoracic chaetiger 7 in M. acanthophora , M. multicristata , M. nates and M. taenia , and chaetigers 5–6 in the other six species (Table 1).

Nine species of the genus Metavermilia ( M. acanthophora , M. gravitesta , M. nates , M. ovata , M. truncata , M. yamazotoi , M. spicata , M. acanthophora , M. inflata ) have been reported from Japan. Two of those species, M. inflata Imajima, 1977 and M. spicata Imajima, 1977 were described from off the Ogasawara Island, near the type locality of M. ogasawaraensis n. sp., but from shallow reef locations. However, morphologically M. ogasawaraensis n. sp., appears to be most similar to the Chinese Metavermilia nanshaensis , as both have simple conical opercular covered with flat distal plate and thoracic membranes to chaetiger 4. The two species differ in morphology of their tubes, with without longitudinal ridges but with flaring peristomes in M. ogasawaraensis n. sp., lacking longitudinal ridges but with flaring peristomes and without peristomes but with three longitudinal ridges in M. nanshaensis with tubes lacking peristomes but with three longitudinal ridges in. A further difference between these two species lies in number of teeth of thoracic uncini, being 7–9 in the new species versus 13–14 teeth in M. nanshaensis (Table 1).

Another species morphologically very similar to the new species is M. annobonensis which has having a simple conical operculum with concave distal plate lacking a central tubercle and short thoracic membranes. This species, previously known only from Annobon, West Africa, had been recently reported by Wu et al. (1980) and Sun & Yang (2001) from waters off China. Unlike M. ogasawaraensis n. sp., M. annobonensis has tubes with 4–6 longitudinal keels and 7 teeth in thoracic uncini.

Etymology. The species name is derived from its type locality Ogasawara Islands.

Figures

FIGURE 1. Metavermilia ogasawaraensis n. sp. A, holotype crown and trunk. B, operculum of paratype NHM- 2006.2039. C, anterior part of tube of holotype. Scales are 1 mm (A, C), 0.5 mm (B).

FIGURE 4. Operculum of Metavermilia species. A— multicristata. B, C— taenia. D, E— annobonensis. F— nates. G— arctica. H, I— acanthophora. J— yamazatoi. K— gravitesta. L— spicata. M— truncata. N, O— inflata. P, Qovata. R, S— ogasawaraensis n. sp. T, U, V— nanshaensis. Figures are drawn from the figures of paper, traced using black ink on the transparent sheet. A to F after Zibrowius (1971), G from Kupriyanova (1993), H to Q after Imajima (1996), R and S are original, T—V after Sun (1998).