Bathyvermilia eliasoni Zibrowius 1970, n. comb.

Bathyvermilia eliasoni (Zibrowius, 1970) n. comb.

(Figs. 3 & 4)

Vermiliopsis langerhansi non Fauvel, 1909 sensu Southward 1963: 584 fide Zibrowius 1973: 431.

Vermiliopsis (gen?) eliasoni— Zibrowius, 1970: 121 –122; in ten Hove 1975: 55, 58; in Campoy 1979: 760; in Ariño 1987: 2.141 (Spain); Tyler & Zibrowius 1992: 220 (SW Ireland); in Lommerzheim 1979:154, 1981: 31 (a discussion of the operculum only); Barrier et al. 1989: 790 –791, Fig.2 (a table summarizing depth distribution from 200–2000 m) (Sicily); in Ben-Eliahu & Fiege 1996: 36; in Leahy et al. 2003: 48 (off Ireland); in ten Hove & Kupriyanova 2009: 91, 102.

Remarks. According to Zibrowius (1973) who examined material of Southward (1963), Vermiliopsis langerhansi reported in her paper should be attributed to V. eliasoni. An unpublished record (ten Hove, pers. comm) comes from Tydeman Selvagens-Canary Isl. Exp.1980 CANCAP-IV, Sta. 4.107: Selvagens Archipelago; 30°03'N 15°52'W; depth 2100–2500 m; 2.4 m Agassiz trawl; 26/ 27-V-1980. ZMA V.Pol. 4247, ex NNM 18289.

Material studied. FMHN 6185 (tube fragments), FMHN 6189 (2 specimens), FMHN 6205 (1 specimen), FMHN 6210 (1 specimen). For detailed collection data see Table 1.

Description. TUBES: white opaque, with smooth surface, more or less circular in internal cross-section, with 3 longitudinal denticulate keels, no peristomes (Fig. 3 B), attached to substratum throughout their length.

BRANCHIA: with 7–10 pairs of branchial radioles arranged into semicircles. No inter-branchial membrane, no stylodes, each radiole ends in a thick filamentous tip as long as pinnulae.

PEDUNCLE: more or less circular in cross-section, slightly thicker than normal radioles and clearly inserted as a second radiole. Deep constriction at junction of basal part of operculum and peduncle (Fig. 3 A).

OPERCULUM: inverted cone with white calcareous slightly depressed endplate (Fig. 3 A). Pseudoperculum absent.

COLLAR AND THORACIC MEMBRANES: penta-lobed, with 2 latero-dorsal lobes and ventral lobe divided into 3 lobes. Thoracic membranes short, continuing to thoracic chaetiger 3.

THORAX: Seven thoracic segments, 6 with uncini. Collar chaetae simple limbate of two sizes (Fig. 4A). Rest of chaetae simple limbate plus Apomatus- chaetae (Fig. 4B). Thoracic tori slightly shifted ventrally from mid-lateral line of thorax, but distinct triangular depression absent. Thoracic uncini saw-shaped with 5–6 teeth and pointed anterior fang (Fig. 4D).

ABDOMEN: Achaetous region between thorax and abdomen short. Anterior abdominal chaetae flat, narrow geniculate with blunt teeth (Fig. 4C), replaced by capillary chaetae on most posterior segments. Anterior abdominal uncini saw-shaped with 5–6 teeth and simple blunt pointed anterior tooth. Uncini of middle and posterior abdominal segments rasp-shaped, with 6 teeth in profile and 2–3 teeth per row (Fig. 4E).

COLOUR. No records.

Remarks. The attribution of Vermiliopsis (?) eliasoni to this genus has been questioned already by the author of the species (Zibrowius 1970) and later by ten Hove (1975: 58). According to the original description, the thoracic membranes of V. eliasoni end at thoracic segment 2, but they typically form an apron in Vermiliopsis. The operculum of V. eliasoni is covered by a white calcareous endplate, whereas in Vermiliopsis the opercular re-enforcement is a flat to conical chitinous endplate. The insertion of the peduncle in Vermiliopsis eliasoni was “not exactly known” in the material available to ten Hove (1975: 58). Zibrowius (1970) states “Premier filament dorsal àu gauche ou à droite transformée en pédoncule operculaire, sans barbules ni ailerons” (First dorsal filament to the left or right turned into opercular peduncle, without pinnules or fins). However, ten Hove & Kupriyanova (2009) outlined the controversy regarding which radiole is ontogenetically modified into the peduncle. They argue that the peduncle in serpulids with indirect opercular ontogeny (sensu ten Hove 1984) is actually the modified second dorsal-most radiole, but in large-bodied serpulids the peduncle migrates during development in such a way that it appears to be formed from the first radiole. Often the peduncle is located just below and between the first and second radiole, which easily can be interpreted as transformed first radiole.

Short thoracic membranes, chitinous endplates encrusted by calcareous deposits and cylindrical peduncles inserted as second dorsal filaments are typical for Bathyvermilia Zibrowius, 1973 (sensu ten Hove & Kupriyanova 2009). Because our material fits well the original description of V. (?) eliasoni (with the exception of the discrepancy in the position of the peduncle) and the structure of the tube with denticulate keels is very characteristic, we here attributed the serpulid to B. eliasoni and transferred this species to the genus Bathyvermilia Zibrowius, 1973.

Figure 3 A suggests the presence of very small distal wings on the opercular peduncle, which seems to be different from the original description. However, these “winglets” are a result of very deep opercular constriction and slightly flattened distal end of the peduncle. Zibrowius' original figures show the lateral side of the operculum and the peduncle thus obscuring the width extent of the peduncle.

FIGURE 4. SEM micrographs of chaetae in Bathyvermilia eliasoni n. comb. (FMNH 6189). A—bundle of simple limbate collar chaetae of two sizes, B— Apomatus chaetae of 3rd thoracic chaetiger, C –chaeta of 15th abdominal segment, D—uncini of 2nd thoracic segment, E –uncini of 10th abdominal segment. Scale. A–E—10 µm.