Bithynia shapkarevi n.sp., a new species from Prespa Lake, R. Macedonia (Gastropoda: Bithyniidae)

From Macedonia only Bithynia prespensis Hadžišče, 1963 is known so far. Recent investigations in Prespa Lake revealed a new Bithynia species, Bithynia shapkarevi n. sp. which is described here. Holotype and a paratype in addition to the penis morphology are depicted. The new Bithynia species has been compared with all known Bithynia spp. from the surrounding countries.

From Macedonia only Bithynia leachii (Sheppard, 1823) has been reported (Bank 2011) which has possibly been confused with Bithynia prespensis Hadžišče, 1963, both are of the same size and have swollen whorls, however, the southernmost records of B. leachii are known from Hungary (Glöer & Georgiev 2012).Recent investigations in Prespa Lake revealed a second Bithynia species, distinct from B. prespensis and new for science.
This paper is intended to (i) expand the knowledge about the biodiversity of Macedonia and (ii) to describe the new Bithynia species mentioned above.

Material and Methods
The specimens of new species were collected from Macedonian part of the Prespa Lake, near village Asamati, from 4 m depth (Fig. 1).Bottom samples were taken with an Ekman's grab (225 cm 2 ) and preserved in 75% ethanol.
The dissections and measurements of the genital organs and the shells were carried out using a stereo microscope (Zeiss), the photographs were made with a Leica digital camera system.The type material is stored in the Zoological Museum of Hamburg (ZMH).The species has been compared with all known Bithyniidae of the surrounding countries.Paratypes: 1 specimen, ZMH 79897, 1 specimen coll.Slavevska-Stamenković, 1 specimen coll.Glöer, 2 specimens destroyed by dissection.
Etymology: Named in memory of Prof dr Jonče Šapkarev, in appreciation of his significant contribution for zoological science in R. Macedonia.

Description
Shell.The light yellowish to horn-coloured conical shell is glossy, the surface is finely striated.The 4.5 whorls are slightly convex with a clear visible but not deep suture (Figs.2-3), umbilicus closed, the aperture height takes 0.5 of the shell height.The females are as large as the males, thus a sexual dimorphism is not visible.The operculum is oval.Shell height 4.5-4.8mm, width 3.2-3.3mm.All shells have been covered with a thin layer of chalk.
Soft body.The mantle is light with reticular dark patterns.The head is grey with a whitish snout.Morphology of the penis.Penis and penial appendix are very short.The distal part of the penis is as long as the penial appendix (figs 5, 6), the flagellum is long (Fig. 4).
Differentiating features: Penis, flagellum and operculum are similar to Bithynia prespensis, but the whorls are less convex as in B. prespensis, sutures less deep and no sexual dimorphism as found in B. prespensis.There is no Bithynia species known in the Balkan which has such a short distal part of the penis than the species from Prespa Lake.

Habitat and ecology:
The new species was found from the shallower part of the lake (4 m depth), among sand and silt bottom sediment from the type locality.

Figure 1 .
Figure 1.Map of the study area with the sampling site of Bithynia shapkarevi n. sp.