Cochlostoma partioti (Moquin-Tandon, 1848)

Gofas, Serge, 2001, The systematics of Pyrenean and Cantabrian Cochlostoma (Gastropoda, Cyclophoroidea) revisited, Journal of Natural History 35 (9), pp. 1277-1369 : 1294-1298

Cochlostoma partioti (Moquin-Tandon, 1848)

(®gures 12±16)

Cyclostoma (Pomatias) partioti Moquin-Tandon in de Saint-Simon, 1848: 36 ±37. Type locality: Cirque de Gavarnie (Hautes-PyreÂneÂes, France). One syntype from Gavarnie, coll. Germain ex Saint-Simon.

Pomatias partioti var. crosseana Saint-Simon, 1867a: 11 ±12. Type locality: Cirque de Gavarnie and Pas de l’Echelle near Saint-Sauveur.

Pomatias lapurdensis Fagot, 1880a: 21 (in reprint). Type locality: inside Espelugues cave , near Lourdes (Hautes-PyreÂneÂes; now inside the Lourdes sanctuaries).

Pomatias neglectus Fagot, 1891: 291 (133 in reprint). Type locality: castle of Lourdes; surroundings of Espelugues cave and Pic du Grand Ger (Hautes-PyreÂneÂes).

Cochlostoma (Obscurella) loebbeckei Kobelt, 1902: 502 (unneeded replacement name for Pomatias lapurdensis ).

Description

Shell up to 11.6 Ö 4.8 mm, with 8 to 8.5 quite rounded whorls. Early whorls with a peripheral angle which is totally concealed by the suture; body whorl very slightly constricted, rounded.

Sculpture very weak, shagreened, on the ®rst embryonic half whorl, then with very ®ne axial ribs on the following one and one half whorls. Spire whorls with ®ne, crowded ribs (12±13 ribs/mm) becoming even more crowded (up to 17 ribs/mm) on the body whorl; no terminal thickening of ribs along the suture.

Aperture thickened and expanded into a collar, without a distinct rim inside. Peristome distinctly auriculated, then quite abruptly narrowing and slightly deēcted inwards at the columellar insertion; not distinctly auriculated at the parietal insertion.

Shell colour as in C. obscurum , tawny, with a series of brown subsutural blotches, an interrupted suprasutural brown band continued on the periphery of the body whorl, and a narrow, continued peri-umbilical brown band. Whitish intervals between brown blotches formed by pale segments of the ribs. Peristome white.

Female genital system as in general description, male with a characteristic`key shaped’ penis cylindrical along its proximal half, then distally ¯attened, broadening and with a tapering end.

Remarks

This species resembles C. crassilabrum , but sympatric C. crassilabrum and C. partioti , even juvenile, are usually easily discriminated. The latter are smaller with a narrower spire, but the most useful character is the ribbing of the early postlarval whorls which is coarse in C. crassilabrum and evenly ®ne in C. partioti . The shape of the penis, broader in its distal part in C. partioti , is also a discriminating character. It is sometimes stated (e.g. Germain, 1931: 577), that C. partioti has a more uniform colour than C. crassilabrum , but in fact its colour pattern is basically the same as in C. crassilabrum , sometimes even brighter and more contrasted.

Raven (1990) considered C. partioti within the intraspeci®c variability of C. obscurum (there including also montane populations here assigned to C. crassilabrum ), arguing the occurrence of intermediate forms. From the ribbing pattern of early whorls, a specimen of C. partioti (probably a male) can be recognized in his ®gure 14 which is given as an example of a transition (compare with the ribbing of C. crassilabrum , his ®gure 13). I rebut this view on the basis of both conchological diOEerences, and the electrophoretic data which demonstrate two separate, sympatric species. The specimens used for electrophoresis were collected within metres from each other, and the most polymorphic and informative loci (LAP, IDH, ODH) were examined for signi®cant series (20`crassilabrum ’ morphs, 20`mabillianus ’ morphs and 30`partioti ’ morphs). Results regarding ODH cannot be interpreted because G and H alleles migrate too little apart to allow the recognition of heterozygotes. Conversely, the IDH heterozygote s are extremely clear and show the characteristic pattern of a dimeric enzyme ( Richardson et al., 1986: 23).The heterozygotes for LAP are also well identi®ed if the gels are processed quickly, without incubation. The allelic frequencies of LAP and IDH demonstrate reproductive isolation between C. partioti and C. crassilabrum (table 2).

There has been some confusion in the illustrations given by Germain (1931) for this species, although the description is correct. The shell ®gured as C. crassilabris is C. partioti , and that ®gured as C. partioti is C. nouleti .

Habitat

Among limestone, with a preference for shaded surfaces of for inside loose mounds of large blocks. C. partioti is not characteristic of higher altitudes as has often been written (e.g. Germain, 1931: 577; Raven, 1990: 31). It is more common than C. crassilabrum at Arudy (altitude 500 m) and disappears at a lower level than C. crassilabrum (around 1000 m instead of around 1500 m) in the valley of Eaux Bonnes/Gourette.

Range

Endemic to the valleys of Lourdes/Gavarnie (Hautes-Pyr eÂneÂes), Ossau (PyreÂneÂes- Atlantiques), and the upper part of the valley of Rio Ara (Huesca).

The population on the south Pyrenean slope is isolated by the main divide of the Pyrenees, and it is not certain that there is continuity between the two valleys of the north slope. The population from Bielsa (Huesca) recorded as C. partioti by Fagot (1907) is C. crassilabrum .