Hyalopomatus mironovi Kupriyanova, 1993

Kupriyanova, Elena K., Nishi, Eijiroh, Kawato, Masaru & Fujiwara, Yoshihiro, 2010, New records of Serpulidae (Annelida, Polychaeta) from hydrothermal vents of North Fiji, Pacific Ocean, Zootaxa 2389 (1), pp. 57-68 : 59-62

Hyalopomatus mironovi Kupriyanova, 1993

( Fig. 1 , 2 )

Hyalopomatus mironovi Kupriyanova 1993: 148–150 , fig 2a–h.

Hyalopomatus mironovi — Beaulieu 2001 (name only, material identified by Harry A. ten Hove) Hyalopomatus mironovi — Bastida-Zavala 2008: 21 , fig. 5I–J (drawing from Kupriyanova 1993)

Material studied. SAM E3728 , North Fiji Basin, “Jason-2” dive # 149, 16º59.48'S 173º54.89'W; 1991 m, 28 May 2005, 3 specimens ; SAM E3605 “Jason-2” dive # 150, 16º59’32.8”S 173º55’01”E, 1973 m, 29 May 2005, 2 specimens ; SAM E3729 “Jason-2” dive # 153, 173º54.88'W 16º59.43'S, 1985 m, 1 June 2005, 3 specimens (including one prepared for SEM).

Description (for terminology, see ten Hove & Kupriyanova 2009)

TUBE: white opaque, up to 1.6 mm wide with lumen up to 1.3 mm. Semicircular to circular in cross section without external hyaline layer, and without wide flaring peristomes, but with anterior collar-like rings. Medial keel absent. Hyaline granular layer absent.

BRANCHIAE: each lobe with 7–13 branchial radioles, arranged pectinate, not connected by branchial membrane. Branchial eyes absent. Stylodes absent.

PEDUNCLE: smooth circular, slightly thinner than radioles, inserted just below first and second radiole. Pair of lateral wings proximal to opercular bulb absent. Constriction present just below opercular bulb. Pseudoperculum absent.

OPERCULUM: transparent globular or pear-shaped without differentiated endplate. Length of the operculum about 1.2 mm ( Fig. 2A, C ).

COLLAR and thoracic membranes: collar high, completely covering branchial lobes, with entire margin; with ventral lobe wider and longer than the lateral ones ( Fig. 2B ). Collar continuous with thoracic membranes, ending between chaetigers 3 and 4 ( Fig. 2B ). Pairs of small, wart-like protuberances of collar chaetiger absent; tonguelets between ventral and lateral collar parts absent.

THORAX: with collar chaetiger, and 5 uncinigerous chaetigers ( Fig. 2B ). Collar chaetae of two types: fin-and-blade with fin well separated from the blade by gap ( Fig. 1A ) and simple limbate chaetae. Subsequent chaetae limbate, of two sizes; Apomatus -chaetae absent ( Fig. 1B ). Uncini along entire thorax rasp-shaped, with ca. 28 rows of teeth in profile view; row proximal to peg with 8 teeth; with 6–5 teeth in middle and posterior rows, peg divided into 4–5 rounded lobes ( Fig. 1E ). Prostomial eyes absent.

ABDOMEN: Uncini rasp-shaped with 6–8 teeth in horizontal row and ca. 26 teeth in profile view ( Fig. 1G ). Chaetae ending in long narrow tip with pointed teeth arranged in two rows at the base of the tip ( Fig. 1C, D ). Capillary chaetae present in posterior chaetigers. Posterior glandular pad absent.

SIZE: length up to 18 mm. Width of thorax up to 1.2 mm. Branchiae and operculum approximately one third of total length, length of the operculum about 1.2 mm ( Fig. 2A, C ).

COLOUR of live specimens: white ( Fig. 2 ).

Remarks. This species was originally described from the Kurile-Kamchatka Trench ( Kupriyanova 1993) from the depths of 5,202 – 5,110 m. Additional specimens were later collected on stalks of glass sponges Hyalonema 220 km off California by S. Beaulieu from the depth of 4,100 m and identified by H. A. ten Hove ( Bastida-Zavala 2008).

Hyalopomatus mironovi differs from all previously described Hyalopomatus species by the very prominent smooth gap between the fin and the blade of the collar chaetae ( Fig. 1A ). It resembles H. claparedii Marenzeller, 1878 and H. langerhansi Ehlers, 1887 in having a simple membranous vesicular operculum without any traces of an endplate. In addition to lacking special fin-and-blade collar chaetae, H. claparedii differs from H. mironovi in having only 2–3 lobes in pegs of abdominal uncini and tubes with smooth shiny surface. H. langerhansi is very poorly known, its most recent description in Zibrowius (1969) is a summary taken from Ehlers (1887) and the type material is badly damaged ( Hartman 1938), so no further details are available. Therefore, structure of the special collar chaetae remains the only reliable distinguishing character for H. langerhansi and H. mironovi .

Bastida-Zavala (2008) states that operculum in this species is “pear-shaped with distal convex plate”. However, he refers to the re-drawn illustration by Kupriyanova (1993) that clearly shows lack of any endplate on the vesicular operculum, which is also stated in the original description ( Kupriyanova 1993). If the Hyalopomatus material collected by Beaulieu (2001) does have opercula with differentiated endplates, it may not belong to H. mironovi .

The present record significantly extends the distribution range of Hyalopomatus mironovi adding the bathyal habitats in the vicinities of the hydrothermal vents of the Central Pacific (North Fiji) to the known abyssal non-hydrothermal locations of the North-Western (Kurile-Kamchatka Trench) and North-Eastern (off California) Pacific Ocean. Currently this extension is based on morphological data only because no comparative DNA sequence material exits for Hyalopomatus mironovi or any other widely-distributed bathyal or abyssal serpulid species. Future collecting and sequencing efforts may confirm the distribution or show presence of several regionally distributed species.

Figures

FIGURE 1. SEM micrographs of chaetae of Hyalopomatus mironovi from “Jason-2” submersible dive # 153. A— special fin-and-blade collar chaetae with fin well separated from blade by a gap, B—chaetae of the first thoracic uncinigerous segment, C—chaeta from the 38th abdominal segment, D—close-up view of the distal part of an abdominal chaeta, E - thoracic uncini of the 2nd uncinigerous segment, F—details of the peg of 2nd thoracic uncini, G—uncini of the 13th abdominal segment. Scale. A–C, E—10 µm, D & F—2 µm, G—5 µm.

FIGURE 2. Live photos of Hyalopomatus mironovi from “Jason-2” dive # 149. A—operculum of the animal inside the tube, B—anterior end of the worm removed from the tube, C—view of the thorax showing the development of the thoracic membranes. (photo G.W. Rouse). Scale. A–C—1 mm.