Brachystomia scalaris (MacGillivray, 1843)

Høisaeter, Tore, 2014, The Pyramidellidae (Gastropoda, Heterobranchia) of Norway and adjacent waters. A taxonomic review, Fauna norvegica 34, pp. 7-78 : 27-30

Brachystomia scalaris (MacGillivray, 1843)

Figures 30-33

Odostomia scalaris - Macgillivray, 1843:154

Odostomia scalaris Macgillivray - van Aartsen & al. 1984; van Aartsen 1987; Peñas et al. 1996; Høisaeter 2009

Odostomia (Brachystomia) scalaris (Macgillivray) - Winckworth 1932

Brachystomia scalaris (Macgillivray) - Smith & Heppell 1991

Zastoma scalaris Macgillivray - Iredale 1915

Odostomia Rissoides Hanley, 1844:18

Odostomia rissoides Hanley – Jeffreys 1848 ; Forbes & Hanley 1850 -51; Jeffreys 1867, 1870; M. Sars 1870; Meyer & Möbius 1872; Friele 1874; G.O. Sars 1878; Norman 1879; Collin 1880; Jeffreys 1884; Petersen 1888; Marshall 1899

Odostomia (Brachystomia) rissoides Hanley - Monterosato 1884 ; Høisaeter 1986

Odontostomia (Brachystomia) rissoides (Hanley) - Dautzenberg & Fischer 1925

Brachystomia rissoides (Hanley) – Ankel 1936; Fretter et al. 1986; Graham 1988; Høisaeter 1989

Ptychostomon rissoides (Hanley) - Kobelt 1903

Chemnitzia pallida (Montagu) (in part) - Clark 1855

Odostomia nitida Alder, 1844:326 - Alder 1848; Jeffreys 1859; Collin 1884

Turbonilla (Odontostomia) nitida Alder - Malm, 1861

Odostomia alba Jeffreys, 1848:337 - Forbes & Hanley 1850 -51; Jeffreys 1859

Type material: Not known.

Type locality: Aberdeen in Scotland.

Material seen: Norway - Skagerrak , 65 spms ; Hordaland, 820 spms; Møre og Romsdal 3 spms; Nord-Trøndelag, 30 spms; Nordland, at least 7 shs.

Diagnosis: Shell: Brachystomia with moderately prosocline growth lines, and a turreted shell shape with quite convex whorls and deep sutures. Rounded aperture. Protoconch (Figures 30 and 31) of type C (intorted) of less than one whorl and with a clear demarcation of the beginning of the first teleoconch whorl. Soft parts: Head foot complex (Figure 32, top) white with numerous small yellow pigment spots scattered over foot and tentacles, tentacles triangular with tentacular pads, mentum slightly expanded at the tip, eyes fairly large and

Figure 27. Brachystomia angusta . A specimen from Grimstad, Aust-Agder (58°20’N, 8°35’E), 2.2 mm (G 33-71).

Figure 28. Brachystomia carrozzai . A specimen from Foldafjorden, 64°40.2’N, 11°07.5’E, 60- 20 m, 2.1 mm (ZMBN 83083).

Figure 29. Brachystomia eulimoides . A specimen from Bøddelhaue, Grimstadfjorden 58°19.5’N, 8°35’E, 35 m, 4.1 mm, and one from Vikkilen, Grimstad, 58°20.7’N, 8°36.7’E, 20 m, 2.7 mm (P.max.-86).

Figure 30. Brachystomia scalaris . A specimen from Hillersholmen, Raunefjorden 60°17.8’N, 5°11’E, 6-8 m, 2.25 mm (ZMBN 83114), and one from Knappensundet, Grimstadfjorden, (Hordaland), 60°19’N, 5°15.8’E, 3.5 m, 1.75 mm (ZMBN 83111).

Figure 31. Brachystomia scalaris , postlarva. Scale bar = 300 µm.

Figure 32. Brachystomia scalaris , head-foot complex and pigmented mantle organ (not to scale).

Figure 33. Brachystomia scalaris , operculum, two views. Scale bar = 200 µm.

not particularly close together. Pigmented mantle organ (Figure 32, bottom) yellow blotch with dark brown interrupted edges, masses of white ‘bubbles’ above and an oblong custard coloured gland further up. Operculum: (Figure 33), flat with only a slight thickening under the central part, no clear indentation for the columellar tooth.

Biology: B. scalaris seems to be a typical shallow water species, rarely found deeper than 15 m in our waters. It has most frequently been encountered as an ectoparasite of Mytilus edulis , but has been reported from a number of other molluscan hosts as well as free living in shallow water ( Ankel & Christensen 1963, Rasmussen 1973, Fretter et al. 1986). In my studies ( Høisaeter 1989), the species was found in samples dominated by Limaria hians and Modiolus , but also in samples of Pomatoceros reefs, and finally from haptera and stipes of Laminaria hyperborea in semi-exposed and fairly protected areas. In the first and last of these it was invariably the most numerous pyramidellid species. Like B. eulimoides primarily a mollusk-feeder, but my studies indicate that it occasionally co-occurs with other pyramidellids on Pomatoceros reefs.

Distribution: Rarely recorded from Norway before 1986. Norman (1879) reports it from Raunefjorden and Osterfjorden and cites earlier reports from Oslofjorden (from Jeffreys 1870). G.O. Sars (1878) records it from Oslofjorden, the southern coast and the west coast. In my material 13 samples with 34 specimens from Skagerrak, and 705 specimens from the Espegrend area. Further north 33 specimens and 39 shells, the northernmost empty shell from southwest of Bodø (67°15’N, 50- 20 m, shell gravel, slag and small stones). A sample from a shallow water algae station (containing more than 1200 Bittium reticulatum ) at Fløan, bay southeast of Stamnes (64°29’N, 3-10 m, soft bottom with Laminaria saccharina , Chorda filum and other algae) contained at least 30 B. scalaris . This is thus at present the northern limit for the species (based on living material). Outside Norway it is known from Sweden and Denmark, even the western part of the Baltic Sea, all around the North Sea, the western and southern coasts of Ireland and the British Isles, further south along the Atlantic coasts of Europe ( Ankel 1936) and the western Mediterranean ( Peñas et al. 1996). Van Aartsen et al. (1998) extend the distribution to Mauritania, and also cite earlier records from Madeira, the Selvagens archipelago and the Azores.

Remarks: Iredale (1915) reinstated the oldest name, O. scalaris Macgillivray , which had been replaced by O. rissoides Hanley by Jeffreys (1848). The reason for this replacement was that Jeffreys regarded all the British pyramidellids as species of Odostomia . When the group was split up into several genera, the homonymy of Melania scalaris Philippi (a synonym of Pyrgiscus jeffreysii ) with O. scalaris was no longer a problem (see van Aartsen 1987).

‘ Brachystomia’ lukisi Jeffreys, 1859

Figures 34 -37

Odostomia Lukisii Jeffreys, 1859:112 .

Odostomia lukisii Jeffreys - van Aartsen et al. 1984; van Aartsen 1987; Peñas et al. 1996

Odostomia Lukisi Jeffreys - Jeffreys 1867

Odostomia lukisi Jeffreys - Marshall 1899 ; Warén 1980; Høisaeter 1968, 2009

Odostomia (Brachystomia) lukisi Jeffreys - Høisaeter 1986

Odostomia (Brachystomia) lukisii Jeffreys - Winckworth 1932

Brachystomia lukisi (Jeffreys) - Fretter et al. 1986; Graham 1988; Høisaeter 1989

Brachystomia lukisii (Jeffreys) - Smith & Heppell 1991

Ptychostomon lukisi (Jeffreys) - Kobelt 1903

Type material: Twelve syntypes, USNM 132156 ( Warén 1980)

Type locality: Not designated, but Guernsey, Channel Islands is the locality of the syntypes .

Material seen: Norway - Skagerrak, 2 shs; Hordaland, 245 spms.

Diagnosis: Shell: Small (usually less than 2.8 mm), glossy, ivory white. Protoconch intorted, extremely flat (type C) (Figure 36). Growth lines more or less vertical. Soft parts: Tentacles (Figure 35 top) short and wide, apparently without tentacular pads, eyes very close together, mentum characteristically cleft, with diverging ends. Pigmented mantle organ (Figure 35 bottom) in two parts, long and yellow above and short oval, brownish yellow below. Operculum: (Figure 37) with a notch at he columellar side, a ventral thickening in the middle, but no typical ‘anchor’ of the ‘ Odostomia’ - type (see Figure 3 ). Frequently with corroded protoconch and corrosion marks on the whorls ( Figure 34 ).

Biology: According to Fretter et al. (1986) frequently found in association with fairly large assemblages of Pomatoceros , and also with Serpula and Spirorbis . This is also the case for the material from Norway, but the association with Pomatoceros is far less strong than what was observed for O. striolata and O. turrita ( Høisaeter 1989) . Thus it was not found at the Pomatoceros -dominated substrate at the Hillersholmen locality, and the three samples at the Knappensundet locality in which it was found in highest numbers (in one sample even with higher abundance than any other pyramidellid) were all typical Limaria-Modiolus dominated samples.

Distribution: A southern, shallow water species, in Norway only recorded from the Espegrend area except for two shells from Skagerrak and a single older record from Florø (61°36’N) ( Høisaeter 1968). All but two specimens in my material from 11 samples from the locality in Knappensundet (Straume bridge) in Grimstadfjorden (60°19’N) (see Høisaeter 1989). Outside Norway it is reported as occurring sparingly both in the Atlantic and the Mediterranean (van Aartsen 1987). According to Graham (1988) it is among the commonest of intertidal pyramidellids on the west coast of the British Isles and the southern Channel, but is absent from the North Sea. Reported from the western Mediterranean by both van Aartsen et al. (1984) (Algeciras Bay) and Peñas et al. (1996). Van Aartsen et al. (1998) extend the distribution to Mauritania, the Canary Islands, Madeira, and the Azores.

Remarks: Spelling of the specific name varies. Originally ( Jeffreys 1859) spelled it with a double ‘i’ at the end, but later ( Jeffreys, 1867) with a single ‘i’. It is explicitely named after Dr. F.C. Lukis. The choice between the two spellings should be solved based on Article 31.1 of ICZN.The crucial point is the question of whether the name is based on a personal name that is Latin, or from a modern name that is latinized. I interpret Jeffreys’ change of mind as an indication that he did not intend to latinize the name. This is not a Brachystomia s.s., as is clearly seen from the soft parts. It occupies, taxonomically, an isolated position in the Norwegian pyramidellid fauna. The population of this species in Norwegian waters may fluctuate wildly from decennium to decennium, dependent on the amount of larvae brought in with water masses of varying origin and temperature.

Figures

Figure 3. Operculae from four species of odostomine pyramidellids. From left, Brachystomia scalaris, Parthenina interstincta, ‘Brachystomia’ lukisi, Odostomia acuta.

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.