THE FIRST RECORD OF PONTOBELGRANDIELLA RADOMAN , 1978 FROM GREECE ( CAENOGASTROPODA : TRUNCATELLOIDEA : HYDROBIIDAE ) WITH THE DESCRIPTION OF A NEW SPECIES

The first species of Pontobelgrandiella Radoman, 1978 from Greece is described as Pontobelgrandiella lavrasi n. sp. Key worDs: Belgrandiella, Pontobelgrandiella, Bulgaria, Greece

Until now, representatives of Pontobelgrandiella have been known from Bulgaria only (GeorGiev et al. 2017, osiKowsKi et al. 2017).Thus, it can be assumed that the easternmost species of Belgrandiella is B. bumasta Schütt, 1960 in Kosovo.It is possible that two other species described from within the distribution area of Pontobelgrandiella in Bulgaria belong to Belgrandiella and not to Pontobelgrandiella: Belgrandiella maarensis Georgiev, 2013 andBelgrandiella zaschevi Angelov, 1959, the type of the monotypic Cavernisa Radoman, 1978. However, rysiewsKa et al. (2016) "undoubtedly reject the occurrence of representatives of Belgrandiella in Bulgaria" (rysiewsKa et al. 2016: 7).In any case, no species of Pontobelgrandiella has been mentioned from outside Bulgaria.

METHODS
The whorls were counted according to GittenBerGer et al. (1970).The shell length and diameter were measured with a 5 mm measure plate (0.05 mm grading) at 25× magnification; measurements were rounded to the nearest 0.05 mm.The photographs of shells were taken with a Leica R8 digital system.

Figs 1-3
Shell description.Shell transparent and smooth, ovoid with conical spire, 4.25-4.50whorls, convex and shallow suture, body whorl especially on its left side in front view below suture hardly vaulted; last fourth of body whorl gradually ascending on shell wall; edge of aperture in side view straight; aperture almost crescentic, parietal margin forming a chord; parietal margin of aperture fused with shell wall and sealing the umbilicus or leaving it short slit-like open; palatal and basal margins of aperture not broadened, but slightly thickened; columellar and parietal margins forming a rounded angle.Measurements (n = 7; type locality): height 1.73-1.98mm (mean 1.83 mm), diameter 0.93-1.03mm (mean 0.98 mm), height : diameter ratio 1.74-1.87(mean 1.84); see also Table 1.
lavrasi n. sp. are less convex, moreover, in P. lavra si n. sp., in frontal view, the left convex vault of

DISCUSSION
Belgrandiella and Pontobelgrandiella inhabit springs and subterranean waters.It is commonly understood that the distribution areas of species of these genera might be quite small.Recently FaLniowsKi & Beran (2015) critically discussed this view for four nominal taxa of Belgrandiella.They argued that "The shell alone cannot be the basis of species discrimination in the Truncatelloidea".However "congeneric species may not differ in their soft parts' morphology and anatomy" (raDoman 1983: 190).Based on their genetic investigations, FaLniowsKi & Beran (2015) stated that their "molecular data strongly suggest that all four nominal species represent one real biological entity: one species, genetically slightly variable".The geographical distance between the most remote investigated populations was about 240 km.
rysiewsKa et al. (2016: 1) studied genetically 16 Bulgarian populations of Pontobelgrandiella, and distinguished four clades.Interestingly, they added that "The Principal Component Analysis of seven shell measurements showed some morphological distinctness of the representatives of the distinguished clades, although with some overlapping variability".They found that the largest geographical distance between populations of the same clade was about 150 km (rysiewsKa et al. 2016: 6, fig. 4, clade II), however, the smallest distance between populations of different clades was less than 10 km (rysiewsKa et al. 2016: 6, fig. 4, clade IV versus clades I and III).This means that the size of the distribution area depends on the specific case.
However, in regard to the discovery of a new species of Pontobelgrandiella, namely P. lavrasi n. sp., in Greece, it should be borne in mind that the distance to the distribution area of the nearest Bulgarian representative of Pontobelgrandiella, P. dobrostanica, is more than 200 km.On the other hand FaLniowsKi & Beran (2015) investigated populations of a "real biological entity" up to 240 km apart, but within the distribution area of Belgrandiella; the locality of P. lavrasi n. sp.lies about 200 km outside of the known distribution area of Pontobelgrandiella species.This fact combined with morphological differences, as described above, supports the status of P. lavrasi n. sp. as a distinct new species.Live specimens are needed to confirm its distinctiveness and its attribution to Pontobelgrandiella by anatomical and molecular studies.
Fig. 4. Type localities of species of Pontobelgrandiella or regarded as belonging to this genus in the Balkans (for numbers see Table2); red dot -P.lavrasi n. sp.

Table 2 .
List of nominal taxa of Pontobelgrandiella or regarded as belonging to this genus in the Balkans and not conical (see anGeLov 1976: fig.1) and the shell height is only1.20-1.40mm (GeorGiev  2011a: 9, table