Odostomia plicata ( Montagu, 1803 )

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

Odostomia plicata ( Montagu, 1803)

Figure 51

Turbo plicatus Montagu, 1803:325

Odostomia plicata (Montagu) - Forbes & Hanley 1850 -51; Jeffreys 1867; Friele 1874; Collin 1880, 1884; Jeffreys 1884; Petersen 1888 (?); Marshall 1900; Winckworth 1932; van Aartsen & al. 1984; Fretter et al. 1986 (in part); Høisaeter 1986; van Aartsen 1987; Smith & Heppell 1991; Peñas et al. 1996; Öztürk et al. 2013

Odostomia cf. plicata (Montagu) - Høisaeter 2009

Odostomia (Brachystomia) plicata (Montagu) - Monterosato 1884

Chemnitzia plicata (Montagu) - Clark 1855

Ptychostomon plicata (Montagu) - Kobelt 1903

Odontostomia plicata (Montagu) - Dautzenberg & Fischer 1925

Type material:

Type locality: Salcombe Bay , Devonshire, Great Britain ( Peñas et al. 1996) .

Material seen: Norway - Hordaland, 2 shs ( ZMBN 16633 ), identified by Friele (1874). See further Distribution below .

Diagnosis: Shell: According to van Aartsen (1987) with nearly vertical (orthocline) growth lines, no umbilicus and only slightly rounded whorls. According to Jeffreys (1867), who compares it with O. turrita , it is ”..narrower and slenderer, thin, transparent, and much more glossy, having a longer and tapering spire, a slight suture, nearly flat whorls, a differently shaped mouth, and no peripheral keel.” Max. length c. 3.5 mm. Soft parts: “Body whitish, with minute and close-set yellow specks; snout (i.e. mentum) small, wedge-shaped, flexible and extensile; tentacles leaf-like, and presenting three equal-sized, angular and flattened sides, which are folded a little inwards, tips rounded but not much inflated; eyes not quite so close together as in some other species, seated on the tentacles, at their inner bases; foot squarish in front and bluntly pointed behind, sole slightly grooved lengthwise on the posterior half.

Operculum: Not known.

Biology: Ankel (1939, 1949a,b, 1959) have described in detail how it feeds on Pomatoceros , but probably based on misidentified O. turrita .

Distribution: Probably not a Norwegian species. O. plicata has been recorded at various times as a Scandinavian species, but every time refuted by a later author. I have looked at a couple of the shells Friele (1874) assigned to O. plicata (see Material seen, above), which were later dismissed as misidentifications by G.O. Sars (1878:374) and Norman (1879), and I agree that these are unlikely to belong to O. plicata . Outside Norway it is reported from all around the British Isles including the Scottish North Sea coast, the north of France, and the Mediterranean ( McKay & Smith 1979, Fretter et al. 1986, Peñas et al. 1996; Öztürk et al. 2013).

Remarks: Unfortunately I have not had access to living specimens of this species, the type of Odostomia . The description of the head-foot complex of Jeffreys, cited above, is not very helpful, except for the mention of the “minute and close-set yellow specks”. Its closest relative morphologically appears to be O. turrita , a species without any such specks (see Figures 59 and 61). According to Jeffreys (1867) O. turrita has often been mistaken for O. plicata . He cautions that due to the frequent confusion with O. turrita , he can vouch for only records from the south and southwest of the British Isles, and he regards it as a southern species. According to Marshall (1900) “This is not a variable species, and no mistake ought to be made about it. It is long, narrow, and tapering, with compressed whorls and shallow sutural lines.” The rightmost photograph shown in Figure 51 above is of poor quality, but fits the description in Jeffreys and Marshall very well. All specimens from Norway I have seen that might be conspecific with the three shown in Figure 51, have more convex whorls and slightly cyrtoconoid spires, and are probably all varieties of O. turrita . One of the drawings of Poul Winther was named O. plicata by Thorson, with locality Gullmarfjorden ( Fretter et al. 1986:609). This drawing looks suspiciously like O. turrita , which is not among the drawings in Thorson’s collection. I suspect that this naming was out of respect for Ankel, who in 1949 and 1959 mentioned O. plicata as a very common ectoparasite of Pomatoceros in Gullmar-fjorden. Ankel did not mention O. turrita , which previously had been reported as common both in the plankton and the benthos at Kristineberg ( Thorson 1946). Due to this possible misidentification, I think all records from southern Scandinavia need reaffirmation. Until further material is available, this species must be treated as a very doubtful member of the Norwegian fauna.