Odostomia acuta Jeffreys, 1848

Høisaeter, Tore, 2014, The Pyramidellidae (Gastropoda, Heterobranchia) of Norway and adjacent waters. A taxonomic review, Fauna norvegica 34, pp. 7-78 : 31

Odostomia acuta Jeffreys, 1848

Figures 38 -42

Odostomia acuta - Jeffreys, 1848:338

Odostomia acuta Jeffreys - Forbes & Hanley 1850 -51; Jeffreys 1859, 1867, 1870; M. Sars 1870; Friele 1874; G.O. Sars 1878; Collin 1880, 1884; Jeffreys 1884; Petersen 1888; Marshall 1899; Friele & Grieg 1901; Dautzenberg & Fischer 1912; Winckworth 1932; Spärck & Thorson 1933; Warén 1980; van Aartsen & al. 1984; Høisaeter 1986; van Aartsen 1987; Høisaeter 1989; Smith & Heppell 1991; Peñas et al. 1996; Schander et al. 2003; Høisaeter 2009

Chemnitzia acuta Jeffreys (in part) - Clark 1855

Ptychostomon acutum (Jeffreys) - Kobelt 1903

Odontostomia (Nisostomia) acuta (Jeffreys) - Dautzenberg & Fischer 1925

Type material: Twenty-one syntypes, no locality, USNM 753712

Type locality: Not designated, presumably British Isles ( Warén 1980)

Material seen: Norway - Skagerrak , 53 spms; Hordaland, 104 spms; Møre og Romsdal 20 spms; Nord-Trøndelag, 3 spms; Nordland, 13 spms; Troms 3 shs .

Diagnosis: Shell: Large conical shells. Body whorl large and round. Aperture oval. Distinct umbilicus. Columellar tooth fairly prominent. Protoconch large with completely exposed nucleus. Soft parts: Foot wide. Parallel-sided tentacles with blunt tips (Figures 40 and 41), no tentacular pads. Mentum with upturned edges forming a gutter. Pigmented mantle organ (Figure 41) of varying length, alternatively dark brown and yellow segments in a linear row, elongated light yellow gland (?) further behind. Head-foot region (Figure 40) with characteristic purplish-brown colour pattern. Operculum: With very strong opercular ‘anchor’ (Figure 42).

Biology: According to Fretter et al. (1986) probably feeding on bryozoans. Found in large numbers on the gelatinous tubes of the polychaete Myxicola infundibulum ( Høisaeter 1989) . Most likely also associated with other tube building polychaetes.

Distribution: Reported from all along the coast, with the exception of east Finnmark (G.O. Sars 1878). In my material competing with O. turrita and O. unidentata in being the commonest species of Odostomia (s.s.). The northernmost shells recorded from a station in Andfjorden, east of Andøya (69°17’N, 65-80 m, coarse shell gravel). Otherwise, fairly evenly distributed along the coast. Two samples from Hordaland with respectively 58 and 29 specimens, and a sample in the material from Skagerrak with 21 specimens. Otherwise only one to six specimens in each sample. Outside Norway it is known from the Swedish west coast and Kattegatt and the northern part of the Sound. All along the western coasts of the British Isles and Ireland, scattered also on the the North Sea coast of Britain (probably absent from the southern parts of the North Sea) ( Fretter et al. 1986). Not known from Iceland or the Faroes ( Schander 1995). Found along the Atlantic coasts of France and Spain and into the western Mediterranean (van Aartsen et al. 1984, Peñas et al. 1996). Van Aartsen et al. (1998) extend the distribution to Mauritania, Cape Verde Islands, the Canary Islands, and Madeira.

Remarks: Specimens inspected alive are easy to identify, but long dead shells are hard to distinguish from O. unidentata . O. acuta is included in the 16S-analysis of Schander et al. (2003), who concluded that its inclusion in Odostomia (represented by O. turrita and a few species not found in the Norwegian fauna, but not the type species, O. plicata ) is “problematic, as it alternately clusters with ‘ Megastomia’ (i.e. ‘ Odostomia’ conoidea and ‘ O.’ corimbensis ), or is basal to other Odostomia species ”. Morphologically O. acuta is most definitely closer to e.g. O. turrita (and especially to O. unidentatata ) than to O. conoidea , and the table of pairwise differences in Schander et al. (2003) support this relationship, as the character difference between O. acuta and ‘ O.’ conoidea is more than twice the difference between O. acuta and O. turrita . O. acuta is among the most common pyramidellids along the Norwegian coast, especially as empty shells.

Figures

Figure 38. Odostomia acuta. Two specimens from Grimseidpollen, W of Pålsholmen, 60°16’N, 5°16’E 20-23 m, 2.4 and 1.45 mm (ZMBN 82595). Figure 39. Odostomia acuta, protoconch of specimen from the same locality as in Figure 36, three orientations Figure 40. Odostomia acuta. A specimen from Bukkasundet, Raunefjorden, 60°14.2 N, 05°12.3’E, 15 m, 3.8 mm. Figure 41. Odostomia acuta, head-foot complex and pigmented mantle organ (not to scale). Figure 42. Odostomia acuta, operculum, two views. Scale bar = 400 µm. Figure 43. Odostomia umbilicaris. Two illustrations from the literature. From van Aartsen (1987) at left and Fretter et al. (1986) at right. The shell at left is Jeffreys’ ‘type’, USNM 132020, the one at right is a shell from the Hebrides. Figure 44. Odostomia umbilicaris. A specimen from the Swedish west coast (Schander 1995, as O. acuta) between two specimens from Biskopshavn, Bergen, 60°25.4’N, 05°17.6’E, 50-60 m, (ZMBN 35030), both 2.95 mm, coll, and det. Friele.