Xerocrassa (Xerocrassa) latastei (Letourneux in Letourneux & Bourguignat, 1887)

Ezzine, Issaad Kawther, Pfarrer, Beat, Dimassi, Najet, Said, Khaled & Neubert, Eike, 2017, At home at least: the taxonomic position of some north African Xerocrassa species (Pulmonata, Geomitridae), ZooKeys 712, pp. 1-27 : 2-4

Xerocrassa (Xerocrassa) latastei (Letourneux in Letourneux & Bourguignat, 1887) Figs 1, 2, 3

1887 Helix latastei Letourneux in Letourneux & Bourguignat, Prodrome de la malacologie terrestre et fluviatile de la Tunisie: 63 [Ketenna et dans le vallon de l’Oued El-Ftour, ainsi qu’à l’oasis du Hammam de Gabès. Plaine entre Ras-el-Aïn et Sidi-Salem-Bouguerara. Bir-el-Ahmar. Bords de l’Oued Medzesar et de l’Oued Taferma entre Aïn-Magroun et Fratis. Ras-ed-Djerf, vis-à-vis de Djerba; Zarzis, etc. (Let.). - En Algérie: Ouled Naïl près de Biskraoù, à Aïn-Gussera, à Bou-Ghezoul sur les hauts plateaux, entre Boghar et Laghouat et entre cette ville et Djelfa].

Type specimens.

Brandt (1959: 113) considered four taxa of hygromiid species described by Letourneux and Bourguignat, 1887 to constitute the species H. latastei . Our investigation of the type specimens of these taxa revealed that the species Helix fratisiana and Helix tafermica , which had been listed by him in the synonymy of H. latastei , belong to species of the Hygromiidae living in Tunisia. In order to stabilize nomenclature, we herewith select MHNG-MOLL 115121 as lectotype for Helix latastei [hic!]. Thus, the type locality of this species is herewith restricted to Ketenna [= Kettana]: mouth of Oued El Ferd, Gouv. Gabés, at 33.7575 10.2047; paralectotypes MHNG-MOLL 115121b/4, MHNG-MOLL 115128/2.

Additional specimens examined.

Bou Hedma, 29.3.1997, leg. J. Gugel, 34.4958°N 9.488°E, NMBE 516753/1; Boughrara, Medenine, 6.12.2015, leg. Ezzine, NMBE 541952/3, ditto, NMBE 547176/3; ditto, NMBE 541955/7 (preserved); Jorf (El Djorf), Mednine, 6.12.2015, leg. Ezzine, NMBE 541956/1 (preserved), NMBE 549907/1 (anat.); "plaine entre Ras-el-Aïn et Sidi-Salem-Bouguerara", MHNG-MOLL 115118/3, MHNG-MOLL 115126/6, MHNG-MOLL 115127/6, MHNG-MOLL 115129/4; Bir-el-Ahmar MHNG-MOLL 115119/1; Zarzis MHNG-MOLL 115120/2; "Oued el Ftour près de Gabès” MHNG-MOLL 115124/6; "Ras-ed-Djerf, vis-à-vis de Djerba" MHNG-MOLL 115125/1. - Specimens recorded from literature: ruins of Gighti close Djorf (Djerba) ( Jaeckel 1963).

Diagnosis.

Shell small to medium sized, thick, basic colour white; protoconch brownish to blackish; three first whorls with granulations; whorls ribbed; suture moderately deep; umbilicus very small, conical.

Description.

Shell small to medium sized, depressed globular, thick, basic colour creamy white; protoconch very small, brownish to blackish, smooth, consisting of 1½ whorls; teleoconch consisting of 5½ slightly flattened whorls, sculptured by moderately sized axial ribs; three first whorls brown with whitish granules; lower teleoconch whorls with up to 5 brown spherical bands; suture moderately deep; underside often white; aperture sub-spherical, slightly descending; columellar peristome thick; umbilicus moderately small, conical.

Genital anatomy.

The description of the genital organs is taken from an adult and mature specimen collected in El Djorf. Figure 1B shows the lumen of the atrium with its internal structures.

Male part. Penis club-shaped, thick; epiphallus longer than penis; penial retractor muscle inserting at the boundary between penis and epiphallus, with a strong fascia enveloping the genitals; flagellum short; penial papilla subdivided in a simple basal shaft and a subsequent part characterised by deep perpendicular grooves, terminal part of the penial papilla strongly kinked, with central pore at its tip.

Genital atrium. Considerably thickened, lumen filled by two structures: 1) a strong crest of fleshy tissue (here called stimulator), auricle-shaped, the interior side (i.e. opposite to the penial papilla) with zigzag-shaped longitudinal pilasters becoming smooth when entering the interior wall of the atrium, and 2) a longitudinal spoon- or tongue-shaped tissue plate (here called internal tissue cone), with the outer rims bent upwards forming a hollow structure.

Female part. Two very small, almost spherical dart sacs in opposite position; glandulae mucosae simple, tubes randomly attached on the vaginal wall between dart sacs and pedunculus; vagina moderately long, pedunculus formed by a quite strong tube.

Measurements. Lectotype latastei : D: 15.9 mm; H: 12.39 mm; PD: 8.58 mm; PH: 6.72; W: 6.25.

Distribution

(Fig. 2). This species is currently known from the coastal and neighbouring inland areas of central and southern Tunisia. It occurs almost in sympatry with H. latasteopsis in some areas of the province Medenine and Sidi Bouzid.

The Senckenberg Museum houses a considerable number of dry shells under the name H. latatstei from Libya, based on the collections of Brandt (1959: 112 ff.). They were examined by Neubert during the last years, and they in fact are very similar to X. latastei from Tunisia. However, all these shells were collected in the Cyrenaica and its hinterland with the westernmost locality being Marsa Brega (ca. 200 km SSW of Bengasi). So far we have not seen any shells from the Sirte nor the Tripolitanian area towards Tunisia, which embraces almost half of the coastal stripe of Libya. The gap to the Tunisian populations is more than 800 km as the crow flies. This area was visited several times by Kaltenbach (Kaltenbach 1950a; 1950b), but there are no records for X. latastei from this area in his rich collection, which is also housed in SMF. As long as no preserved specimens from the Cyrenaica are available, we consider these populations as not conspecific.

Remark.

Specimens of this species are characterized by a globose shell with a quite small umbilicus if compared to the large Cernuella species, which live sympatrically in southern Tunisia.

The internal structures in the genital atrium are poorly understood. However, when dissecting the atrium, the internal tissue cone is always found to almost completely envelop the penial papilla; the situation shown in Fig. 1B is the result of pulling the penial papilla out of the internal tissue cone. Spreading the opened atrium then leads to a position of this organ on the right side.