Odostomia turrita Hanley, 1844

Høisaeter, Tore, 2014, The Pyramidellidae (Gastropoda, Heterobranchia) of Norway and adjacent waters. A taxonomic review, Fauna norvegica 34, pp. 7-78 : 38

Odostomia turrita Hanley, 1844

Figures 58-62

Odostomia turrita - Hanley 1844:18

Odostomia turrita Hanley - Alder 1848 ; Jeffreys 1859, 1867, 1870; Friele 1874; G.O. Sars 1878; Norman 1879; Collin 1880, 1884; Jeffreys 1884; Petersen 1888; Marshall 1900; Norman 1902; Dautzenberg & Fischer 1912; Winckworth 1932; van Aartsen & al. 1984; Fretter et al. 1986; Høisaeter 1986; van Aartsen 1987; Høisaeter 1989; Smith & Heppell 1991; Schander 1995; Peñas et al. 1996; Schander et al. 2003; Høisaeter 2009

Ptychostomon turritum Hanley - Kobelt 1903

Odostomia unidentata var. turrita ? Hanley - Forbes & Hanley 1850 -51

Odostomia plicata? (Montagu) - Friele 1874 (see Norman 1879)

Odostomia plicata (Montagu) - Ankel 1959; Maas 1965; Fretter et al. 1986 (in part) (not O. plicata (Montagu))

Chemnitzia acuta Jeffreys - Clark 1855 (in part)

Type material: A single battered specimen from Guernsey ( Jeffreys 1848) .

Type locality: Herm , near Guernsey, Channel Islands ( Forbes & Hanley 1850 -51) .

Material seen: Norway - Skagerrak , 120 spms ; Hordaland, 8011 spms; Møre og Romsdal 4 spms, at least 2 shs; Nord-Trøndelag, 15 spms at least 4 shs; Nordland, 101 spms, 14 shs; Troms, 1 sh.

Diagnosis: Shell: The smallest of the six species of Odostomia s.s. in the Norwegian fauna, rarely more than 2.5 mm long (max. length measured out of the roughly 8000 specimens was 3.1 mm, and less than 10% of all were more than 2 mm long). Shell shape variable, but usually a rather narrow cone. As opposed to O. plicata with distinctly prosocline growth lines. Protoconch at c. 90° to shell axis, nucleus clearly visible. Soft parts: The foot and tentacles (Figure 59) are comparatively long and flexible as compared to the other species of Odostomia s.s. observed. No tentacular pads. Pigmented mantle organ (Figures 59 and 61) is ‘sealing-wax’ red, easily visible through the shell. The oblong, bright red gland is subdivided by one to several black ‘belts’. With the proviso that not all species in Odostomia s.s. have been observed alive, this colouration is ‘diagnostic’ for O. turrita . Operculum: (Figure 62) with opercular ‘anchor’ smaller than all other members of Odostomia s.s. observed, except O. striolata .

Biology: This is yet another species predominantly, but not exclusively, associated with Pomatoceros . Its feeding biology has been described in detail by Ankel (1959) (as. O. plicata ). Sneli (1972) reported it as feeding on the gills of Homarus , but as remarked by Schander (1995) it is more likely that the single specimen observed was actually feeding on a Pomatoceros specimen on the Homarus shell.

Distribution: Whole coast of Norway, excluding east Finnmark, G.O. Sars 1878. Only empty shells found N of 68°N, however. Norman (1902), based on literature records, included O. turrita in his list from east Finnmark. Not mentioned in Friele & Grieg (1901). In my material more than 8000 specimens and around 500 shells. The northernmost shell from Andfjorden, east of Andøya (69°17’N, 65-80 m, coarse shell gravel). The northernmost specimen from Glomfjorden (66°49’N, 120- 60 m, stones). Otherwise found in all sectors southwards, but whereas O. unidentata is increasing in abundance northwards, O. turrita is decreasing. Ten samples with 34 specimens in the material from Skagerrak. Outside Norway it is recorded from the Mediterranean ( Peñas et al. 1996; Cachia et al. 2001), Mauritania and the Canary Islands (van Aartsen et al. 1998) to most coasts of the British Isles ( Fretter et al. 1986), Ireland, Swedish west coast, the Faroes and Iceland ( Schander 1995), and inner Danish waters (the Sound, Thorson 1946). Recently ( Nekhaev 2011) reported it from the Russian Barents Sea coast near Murmansk.

Remarks: A most variable shell, usually identified by its small size. Easy to identify when alive because of the pigmented mantle organ and the prosocline growth lines. Weak spiral strations may occur, as in many other species of Odostomia . Misidentified by Ankel (1959) and Maas (1965) as O. plicata (See Remarks under O. plicata above).