Bathyditrupa hovei Kupriyanova 1993

Bathyditrupa hovei Kupriyanova, 1993b

(Figs. 2 –3)

Bathyditrupa hovei Kupriyanova, 1993b: 22 –23, fig. 1; ten Hove & Kupriyanova 2009: 29, fig. 9.

Material examined. Type material. SIO: R/V “ Vityaz ” Stn. 5620, 44 °48’N, 156°33’E, 5070 m, 15 Jul 1966 (11 spec.); Stn. 5622, 45 °14’N, 155°15’E, 5110 m, 18 Aug 1966 (2 spec., including holotype); Stn. 5624, 45 °26’N, 154°12’E, 5020 m, 20 Aug 1966 (2 spec.).

Newly examined material. SIO: R/V “ Vityaz ” Stn. 4279, 19 º46.0’N, 120º17.4’W, 4140 m, trawl, 19 Jan 1959 (1 tube); Stn. 4281, 20 º01.3’N, 121º59.6’W, 4370 m, trawl, 21 Jan 1959 (4 spec.); Stn. 5074, 10 º28’N, 140º01’W, 4833 m, grab, 14 Sept 1961 (1 tube); Stn. 6015, 26 º51.5’N, 165º32.1’E, 5850 m, trawl, 24 Apr 1968 (1 spec.); Stn. 7391, 24 º08.3’N, 143º46.1’E, 6330 m, grab, 6 May 1975 (3 spec.).

ZMA: V.Pol. 5325, R/V “ Vityaz ” Stn. 4370, 26 °04.2’N, 153°49.3’W, 6050 m, grab, 3 Mar 1959 (1 spec.); V.Pol. 5326, Stn. 3151, 44 º09.4’N, 170º07.0’E, 5237 m, grab, 24 Sept 1954 (3 tubes).

Description. Tube: free slightly curved Scaphopoda-like, approximately 25 mm long, open at both ends; quadrangular in cross-section outer part, and circular internal opening. No outer hyaline layer, tube surface with traces of growth rings (Fig. 2 C–E).

Branchial crown: Four-six pairs of radioles not joined by inter-radiolar membrane. Branchial eyes not visible in preserved material. Stylodes absent.

Peduncle: inserted as 2nd dorsal radiole, about five times thicker than radioles, slightly flattened, with pinnules (Fig. 1 B). Pair of lateral wings proximal to opercular bulb and pseudoperculum absent.

Operculum: funnel-shaped, covered with concave brown chitinous endplate (Fig. 2 B, D); opercular bulb continuing smoothly into peduncle, constriction absent.

Collar and thoracic membranes: collar not subdivided into lobes (unlobed), slightly shorter laterally than dorsally. Medium-sized incision along the ventral mid-line may present. Thoracic membranes reaching up to 2nd chaetiger, about same width throughout.

Thorax: with five thoracic chaetigers, four of which uncinigerous (Fig. 2 A). Collar chaetae as few short capillaries (Fig. 3A); other thoracic notochaetae, with short limbate blades slightly bent distally, special collar chaetae absent. Apomatus chaetae absent (Fig. 3B). Thoracic uncini saw-to-rasp-shaped with numerous teeth in profile view (Fig. 3D); front view with several rows of teeth and laterally gouged blunt anterior peg.

Abdomen: abdominal uncini similar to thoracic ones, but 1.5 times smaller (Fig. 3E). Abdominal chaetae as short capillaries, slightly longer on posterior segments (Fig. 3C); each chaetiger with a single chaeta.

Size: up to 15 mm in total length, including branchial crown up to 3 mm.

Colour: unknown.

Remarks. This species characterised by its very distinct tubes was originally described from depths of 5050– 5620 m in the Kurile-Kamchatka Trench. The material described here was compared with the type material and other specimens collected by the R/V “ Vityaz ” (Stn. 3151 and Stn. 4370) from the Pacific Ocean already reported by ten Hove & Kupriyanova (2009). Three specimens from Stn. 7391 differ from the remaining specimens including the type material in the shape of the tubes which, unlike almost perfectly quadrangular tubes of B. hovei, are slightly twisted and have slightly rounded edges and distinct growth marks (Fig. 2 C, D). Whether the specimens show intra-specific variability or do belong to a different species needs to be examined further within a framework of a much needed revision.

Distribution. North and Central Pacific Ocean, abyssal, 4104–6330 m.