Parthenina interstincta (J. Adams, 1797 )

Høisaeter, Tore, 2014, The Pyramidellidae (Gastropoda, Heterobranchia) of Norway and adjacent waters. A taxonomic review, Fauna norvegica 34, pp. 7-78 : 16-18

Parthenina interstincta (J. Adams, 1797)

Figures 6-11

Turbo interstinctus J. Adams, 1797:66 . Neotype assigned and nomenclature discussed by Warén (1991). See Remarks below.

Chemnitzia interstincta (Montagu) - Clark 1855

Odostomia interstincta (Montagu) - Alder 1848; Forbes & Hanley 1850 -51; Jeffreys 1867; Friele 1874; Norman 1879; Jeffreys 1884; Marshall 1900

Odostomia (Parthenia) interstincta (Montagu) - Collin 1880

Parthenia interstincta (Montagu) - G.O. Sars 1878; Collin 1884; Petersen 1888

Pyrgulina (Parthenina) interstincta (Montagu) - Dautzenberg & Fischer 1925

Parthenina interstincta (Montagu) - Kobelt 1903; Schander et al. 2003

Chrysallida interstincta (J. Adams) - Warén 1991; Peñas et al. 1996; Peñas & Rolán 1998; Høisaeter 2009

Jaminia obtusa T. Brown, 1827:22

Chrysallida obtusa (Brown) - Høisaeter 1965; van Aartsen 1977; Høisaeter 1989; van der Linden & Eikenboom 1992; Micali et al. 1993

Chrysallida (Parthenina) obtusa (Brown) - Winckworth 1932; Høisaeter 1986; Smith & Heppell 1991; van Aartsen et al. 2000

Type locality: Bigberry Bay , Devonshire. Great Britain .

Type material: Not found ( Warén 1991). Neotype selected by Warén (1991), RAMME 4241.

Material seen: Norway - Skagerrak , 35 spms ; Hordaland, 1250 spms; Møre og Romsdal a few shs; Nord-Trøndelag, 13 spms; Nordland, 41 spms; Troms, 1 spm..

Diagnosis: Shell: usually a moderately tall cone with distinct axial costae, ending at lower of two less distinct spiral threads. Further characterized by conspicuous columellar tooth and deep and shouldered suture. No periostracum. Larval shell of type B (Figures 6 to 8).

Soft parts: Foot long, truncated anteriorly and ending in a blunt point, triangular tentacles with terminal pads, yellowbrown to dark brown pigment in a strip on the inside of the tentacle from just before the eyes and to the end of the tentacle groove, eyes fairly small, mentum blunt, short and narrow, pigmented mantle organ a yellow oval blotch with brown margin, white speck at upper right (Figure 9). Operculum: Having a tubelike internal process and without marginal notch (Figure 10).

Biology: A single specimen reported by Cole & Hancock (1955) from an oyster in a population severely infected by Brachystomia eulimoides . To my knowledge this is the only report on a possible host for P. interstincta . The species was found together with six other pyramidellid species on various substrates in Knappensundet, and with five others from a similar habitat at Hillersholmen (both around 60°16’N, Høisaeter 1989). P. interstincta was consistently present at the three substrates ( Pomatoceros , Modiolus / Pomatoceros , Modiolus / Limaria ) studied, but usually in relatively small numbers in comparison to four other species found. The only samples in which it was close to the dominant pyramidellid species was a soft bottom “covered” with living Limaria hians and Modiolus modiolus . It was also found in samples dominated by Pomatoceros triqueter , but always in low numbers. The results support the theory that P. interstincta is a species feeding primarily on mollusks but that stray specimens might also try to feed on serpulids (in many ways a parallel to Brachystomia scalaris ).

Høisaeter (1965) described spermatophores in this species (as Chrysallida obtusa ) (Figure 11). This was the first record for members of this family. Since then Robertson has described spermatophores in several taxa of pyramidellids from the western Atlantic, and used the different forms partly as a basis for genus level taxonomy ( Robertson 1966; 1967; 1978; 1996). A similar view adopted by Hori & Kuroda (2001).

Distribution: In Norway previously reported from Lofoten (rare) and south along the coast to Oslofjorden (G.O. Sars 1878). In my material common in the Espegrend area (Hordaland, 60°16’N), and sparingly further north, but still not uncommon in the Bodø area around 67.5°N, (37 specimens in the material from Wikander). A single specimen from the species rich station in Gratangen (68°44’N, 90- 80 m, fine shell sand with many Modiolula shells) is so far the northernmost location. Outside Norway known from Southwestern Iceland and off most coasts of the British Isles, south to the western Mediterranean ( Fretter et al. 1986, Warén 1991).

Remarks: Warén (1991) argued that J. Adams’ figure of Turbo interstinctus was not more questionable than those of several others that have been accepted as valid. He therefore suggested that J. Adams’ name, as used by Montagu (1803) and Jeffreys (1867) should be retained in preference to C. obtusa (a name reintroduced by Winckworth 1932). He designated one of two specimens from Montagu’s collection as neotype (figured as Figure 39C in Warén 1991). Van Aartsen et al. (2000) disagreed and presented a long argument for why Turbo interstinctus of J. Adams is not the species that Montagu (1803) called Turbo interstinctus , which is the interpretation of interstinctus adopted by all authors since the time of Jeffreys (1867:153). They first rejected Warén’s selection of one of the shells in Montagu’s collection labelled Turbo interstinctus as neotype of Turbo interstinctus J. Adams , and then in the next paragraph selected the same shell as neotype of Jaminia obtusa Brown, 1827 . I find the reasoning of Warén (1991) convincing, and thus accept P. interstincta as the name of this common and widely distributed species. This common, mainly shallow water species is quite variable, as is illustrated by several SEM-photos in Peñas & Rolán (1998). It is possible in most samples (especially two shallow water, hard bottom stations just southwest of Bodø, 67°16’N, 13 m, and 67°17’N, 50- 20 m) to distinguish two forms, one with broadly conical shape, evenly rounded whorls, the other rather narrow cylindrical, with more flattened, somewhat ‘overhanging’ whorls. In good samples of live-caught specimens, both extremes as well as several intermediate specimens are found, however.