Cochlostoma hidalgoi ( Crosse, 1864 )

Gofas, Serge, 2001, The systematics of Pyrenean and Cantabrian Cochlostoma (Gastropoda, Cyclophoroidea) revisited, Journal of Natural History 35 (9), pp. 1277-1369 : 1310-1311

Cochlostoma hidalgoi ( Crosse, 1864)

(®gures 24±27)

Pomatias hidalgoi Crosse, 1864: 24 , pl. 2 ®gure 3. Type locality: PenÄa de Gorbea and OrdunÄa (Vizcaya, Spain). Lectotype ( Gofas, 1989) and paralectotypes in coll. Journal de Conchyliologie, MNHN. One paralectotype in coll. Bourguignat, MHNG.

Pomatias hispanicus Bourguignat , in Saint-Simon, 1869: 6 ±7. Type locality: near Oviedo (Asturias, Spain). Syntypes: three shells in coll. Bourguignat, MHNG .

Description

Shell up to 15 Ö 7 mm with 7.5 to 8.5 quite rounded whorls. Early whorls with a peripheral angle which may be concealed by the suture or slightly apparent next to it; body whorl slightly constricted, usually with a very slight peripheral angle in prolongation of the suture. Sculpture weak, wrinkled, on the ®rst embryonic half whorl, grading to crowded (25±30 ribs/mm) ribs on the second whorl. Spire whorls with ribs of variable strength, often poorly de®ned, quite widely spaced (6±11 ribs/mm) on third to ®fth whorls, then with ribs becoming gradually more spaced (down to 3±4 ribs/mm) on penultimate whorl; ribs slightly thickened at their termination along the suture. Sculpture often attenuated so as to give the appearence of an eroded shell.

Aperture strongly thickened and expanded into a collar, with a distinct rim inside the outer lip. Peristome distinctly auriculated, gradually narrowing at the columellar insertion.

Shell colour of a uniform reddish brown, paler on the upper spire whorls. Juveniles paler, sometimes with indistinct spiral bands. Peristome white.

Female genitalia as in general description. Male genitalia with a penis ¯attened on one side, of rather constant breadth except for the distal part which is tapering; otherwise like in general description.

Geographic variation

Population s from Basque mountain s (Gorbea, PenÄas de Ranero). The populations from the type locality and surroundings have a robust shell, large for the species, with quite strong ribbing (sometimes as coarse as 3 ribs/mm) and strong apertural collar.

Populations from the coastal area (OrinÄon, Camijanes, Viyao). The shells in these populations are more slender, with a constricted body whorl, ®ner and less acute ribs (not less than 6±7 ribs/mm), with a rather thin and translucent wall. The outer lip is also less thickened. The type specimens of Pomatias hispanicus have this morphology.

Populations around Lago Enol. These are composed of large individuals with a very smooth shell and a well marked discontinuity in the pro®le of the body whorl. Specimens super®cially resemble the smooth and dark C. martorelli (` alopioides ’ morphs) of the OrganÄa canyon; if the locality is not known, specimens can be diagnosed by the diOEerence in columellar insertion (abruptly narrowing in C. martorelli , not so in C. hidalgoi , and on juveniles by the widely spaced ribs on the second whorl of C. martorelli . Allozymic characters show that these forms are unrelated.

There is a peculiar expression of PGD in this population, with a double band on the gels (100/120 or 100/110), which was not found anywhere else. Such bands cannot be interpreted as heterozygote s (`AB’) as there would not be any homozygous individuals for the supposed`B’ allele. It is more likely that this is due to a duplication of the locus, either local or with a null expression in other populations.

Populations in the central area (Ranero, Alisas, La Cabada). This group of populations is physically separated from the western part of the range by a topographical depression devoid of limestone and inhospitable for Cochlostoma . The morphology of specimens from this area is not radically diOEerent from those from the Basque country, but there is consistently a null allele for ODH which was not found elsewhere (®gure 27).

Habitat

Cochlostoma hidalgoi is found on clean rocky surfaces, often among lapiaz. The snails generally estivate on slightly overhanging sites, where they are protected but do not totally avoid rainfall. The availability of such micro-surfaces is a limiting factor for populations.

The separation of habitat between C. hidalgoi and C. bicostulatum is very clear when both species are sympatric. Cochlostoma hidalgoi is then restricted to outcropping bedrock, often in the higher part of this, whereas C. bicostulatum is rather found among rock mounds. The separation is not so clear at Seldesuto, where four species are sympatric, but there is still a trend for C. hidalgoi to prefer the higher, open rock surfaces.

Distribution

Throughout the Cantabrian range, from the Basque country (Aralar, Sierra de Urbasa) to the westernmost palaeozoic limestone outcrops in Asturias. There is one population in France, in the calcareous lapiaz of La Pierre St. Martin (PyreÂneÂes- Atlantiques) (personal information from S. Clanzig).