Ondina coarctata (G.O. Sars, 1878 )

Høisaeter, Tore, 2014, The Pyramidellidae (Gastropoda, Heterobranchia) of Norway and adjacent waters. A taxonomic review, Fauna norvegica 34, pp. 7-78 : 43-44

Ondina coarctata (G.O. Sars, 1878)

Figure 71

Auriculina coarctata G.O. Sars, 1878:205

Auriculina coarctata G.O. Sars - Friele & Grieg 1901

Ptychostomon (Ondina) coarctata (G.O. Sars) - Kobelt 1903

Menestho (Evalea) coarctata (G.O. Sars) - Høisaeter 1986

Ondina coarctata (G.O. Sars) - van Aartsen 1987; Smith & Heppell 1991; Warén 1991; Høisaeter 2009

Type material: Holotype (5.2 mm) NHMO D 1126 and two paratypes USNM 131928 and 132715.

Type locality: Hasvik , western Finnmark, northern Norway, 90-180 m.

Material seen: Norway - Nordland, 1 spm ); Finnmark, Hammerfest 1 sh ( ZMBN 21623 ) (+ Photograph of holotype NHMO D 1126 ) .

Description: Shell: Fairly large for the genus (max. length reported 5.2 mm). Shell with regular fine spirals uniformly covering the whole shell (the shells in Figure 71 are not in good enough condition to show the spiral sculpture). Protoconch small and intorted. Soft parts: Not known. Operculum: Not known.

Biology: Not known.

Distribution: So far known from three shells (type material) from Hasvik in western Finnmark (70°30’N, 90-180 m, G.O. Sars 1878) (Figure 71 left) and a shell from Hammerfest (Figure 71 right). A number of specimens in my material might belong to this species, the one illustrated in Figure 71 (middle) from Nordfjorden (in Melfjorden, Rødøy in Nordland, 66°34’N, 15- 11 m) is the one most similar to the holotype. Outside Norway it is reported from western Iceland (64°21’N, 12°43.5’ W, 162 m) with a single specimen and one shell ( Warén 1991). Whether his specimen from Iceland is conspecific with Sars’ species is not at all obvious from the illustrations in van Aartsen (1987) (holotype) and Warén (1991) (specimen from Iceland) (see discussion below). If this latter specimen is disregarded, the known distribution is between 70°40’N and 66°34’N on the coast of northern Norway.

Remarks: A photograph of the holotype kindly made at my request at the Natural History Museum, University of Oslo (Figure 71 at left) reveals that the holotype is in poor shape. The spiral sculpture may be glimpsed in a few places, but generally it is concealed by ‘fouling’. The general shape of the shell though is close enough to that of my two shells to claim the three be members of the same species. My two shells falls outside the range of variation of the other species known from northern Norway.

According to Warén (1991) O. coarctata resembles O. divisa but is larger, with proportionally shorter aperture, and have stronger spiral sculpture. According to van Aartsen (1987) (who had access to the holotype) O. coarctata differs from O. divisa by a spiral sculpture consisting of many fine spirals present over the total height of all the whorls, of the same strength throughout. G.O. Sars (1878) also describes the sculpture as dense and fine spirals covering the whole shell. ( O. divisa forma nobilis should have more or less the same type of spiral sculpture according to his latin description). O. coarctata is distinguished from O. divisa by a heavier, thicker shell, larger and ‘deeper’ umbilicus, and smaller protoconch. An important difference from O. divisa is, according to G.O. Sars, the comparatively much wider body whorl. This latter character is not obvious in the SEM photo of the specimen from Iceland in Warén (1991). A character of potential importance illustrated in a SEM photo of the top whorls of the specimen from Iceland, ( Warén 1991, Figure 36D) is the spiral sculpture covering the whole of the first postlarval whorl (at least eight spiral incisions). In O. divisa there is only a few spirals at the base of this first whorl. This character is not mentioned in either the original description nor in the brief redescription in van Aartsen (1987). I conclude that the specimen from western Iceland illustrated in Warén (1991, Figures 34F and 36D) do not belong to O. coarctata but to a special form of O. divisa , as this species appears to vary widely geographically (see below).

Figures

Figure 34. ‘Brachystomia’ lukisi. Two specimens from Knappensundet, Grimstadfjorden (Hordaland), 60°19.3’N, 5°15.8’E, 8 m, 2.7 and 1.75 mm (ZMBN 82536). Figure 35. ‘Brachystomia’ lukisi, head-foot complex and pigmented mantle organ (not to scale). Figure 36. ‘Brachystomia’ lukisi, juvenile. Scale bar = 300 µm. Figure 37. ‘Brachystomia’ lukisi, operculum, two views. Scale bar = 200 µm.