Odostomia striolata Forbes & Hanley, 1850

Høisaeter, Tore, 2014, The Pyramidellidae (Gastropoda, Heterobranchia) of Norway and adjacent waters. A taxonomic review, Fauna norvegica 34, pp. 7-78 : 35-37

Odostomia striolata Forbes & Hanley, 1850 -51

Figures 52 -55

Odostomia striolata, Alder - Forbes & Hanley 1850 -51:267 Odostomia striolata Forbes & Hanley - van Aartsen et al. 1984; van Aartsen 1987; Seaward 1990; Smith & Heppel 1991; Peñas et al. 1996; Høisaeter 2009

Odostomia turrita var. striolata (Alder) - Jeffreys 1867; Marshall 1900

Odostomia monterosatoi Bucquoy, Dautzenberg, & Dollfus, 1883:167

Odostomia eulimoides Hanley - Høisaeter 1986 (in part)

Brachystomia eulimoides (Hanley) - Høisaeter 1989

Ptychostomon turritum var. striolatum - Kobelt 1903

Type material: HMAC (Hancock Museum, Alder coll.) (see van Aartsen 1987:27)

Type locality: Northumberland, Great Britain .

Material seen: Norway - Skagerrak, 8 spms; Hordaland, 16 580 spms; Møre og Romsdal 3 spms, 1 sh.

Diagnosis: Shell: Max size 3.3 mm. Convex whorls with dense microscopical striation. Protoconch angle 130°- 140° (type B), ‘nucleus’ almost completely concealed, (see postlarvae, Figure 54). Soft parts: Foot short and wide. Mentum inconspicuous. Tentacles short and wide, somewhat pointed, no tentacular pads. Eyes fairly large and not particularly close together (Figure 53 top). The pigmented mantle organ (Figure 53 bottom) shows a linear row of alternating light red and yellow spots, with a series of bluish white spots above.

Operculum: (Figure 55) of the Odostomia s.s. form but with an opercular ‘anchor’ a little smaller than e.g. the one in O. turrita (cf. Figure 62).

Biology: Of the seven species of pyramidellids found coexisting on Pomatoceros at two localities in the Espegrand area ( Høisaeter 1989), O. striolata (as Brachystomia eulimoides ) was by far the most abundant. Whenever Pomatoceros was absent from a sample, so was O. striolata . During the years from 1963 to 1969 it was twice as abundant as O. turrita , also a typical Pomatoceros ‘inhabitant’.

Distribution: In Norway very abundant in the Espegrend area. In the rest of Norway only found in a few samples the Skagerrak region and from Møre og Romsdal. The northernmost of these is from Fraenafjorden (62°50’N, 62- 50 m, sand, two specimens). Outside Norway it is known from the British Isles and Ireland ( Marshall 1900), Madeira and the Canary Isles (van Aartsen et al. 1998) and the western Mediterranean ( Peñas et al. 1996).

Remarks: The specimen at left in Figure 52 is almost indistinguishable from the photograph of the holotype in van Aartsen (1987) (see van Aartsen et al. 1984 and van Aartsen 1987). The species has the general habitus of O. turrita but is easily distinguished by the partly concealed protoconch (type B) and when alive, the characteristic red and yellow pigmented mantle organ, clearly visible through the shell. The ‘opercular ‘anchor’ is clearly of the ‘ Odostomia’ type although somewhat less developed than for e.g. O. turrita . In the key to Odostomia in van Aartsen (1987), it is keyed out as ‘usually with pronounced spiral striature’. This spiral sculpture is not at all prominent in my material. Jeffreys (1867) united this species with O. turrita , as he thought he found intermediate forms that might belong to one or the other. The species was re-introduced by van Aartsen et al. (1984). In the years 1965-1968 it was by far the commonest pyramidellid in the Espegrand area.

Figures

Figure 52. Odostomia striolata. Two specimens from Pomatoceros-reef, Hillersholmen, Raunefjorden, 60°17.9’N, 05°10.8’, 5-8 m, (ZMBN 82571) both 2.5 mm long. Figure 53. Odostomia striolata, head-foot complex and pigmented mantle organ(not to scale). Figure 54. Odostomia striolata, juvenile. Scale bar = 300 µm. Figure 55. Odostomia striolata, operculum, two views. Scale bar = 200 µm. Figure 56. Odostomia cf.turgida, Holotype of Odostomia turgida (NHMO D1082, 3.2 mm at left) together with a specimen from Femrissund in Sørfjord (Nordland), 67°03.6’N, 13°58’E, 50-30 m, 1.8 mm (T 71039). Figure 57. Odostomia cf. turgida, protoconch of the specimen at right in Figure 54. Figure 58. Odostomia turrita. Two specimens from Pomatoceros-reef, Hillersholmen, Raunefjorden, 60°17.8’N, 05°11.1’, c. 8 m, 1.95 and 1.8 mm (ZMBN 82698). Figure 59. Odostomia turrita, head-foot complex and pigmented mantle organ (not to scale).