Bythinella melovskii n . sp . , a new species from R . Macedonia ( Gastropoda : Hydrobiidae )

A new Bythinella species has been found in the Balkans, Bythinella melovskii n. sp. from Macedonia. The holotypes as well as the penis morphology are depicted. In addition a distribution map of the Bythinella spp. of this region is provided.


Introduction
Bythinella is the most diverse genus of the Rissooidea, of which Yıldırım et al. (2015) counted 132 accepted species in Europe.The species of this genus prefer spring habitats (Boeters 1998) but lives also in spring outlets and associated creeks, rarely in caves and groundwater and in the profundal of Lakes (Boeters & Knebelsberger 2014).
From the W Balkan from Croatia to Montenegro and Serbia 12 Bythinella spp.are known (Glöer & Pešić 2014) while from Albania and R. Macedonia only one species (Fig. 1), i.e.Bythinella drimica drimica Radoman 1976, is known.The species richness of R. Macedonia is possibly underestimated because many parts of this region are unexplored and ongoing investigations in the Balkan are needed.
This paper is intended to (i) describe Bythinella melovskii n. sp. and (ii) to expand the knowledge about the freshwater gastropod diversity of R. Macedonia.

Material and Methods
The snails were collected by hand netting from small streams created by the surplus water draining from the mire complex.Numerous such streams created river Belichka Reka (Jablanica Mt, R. Macedonia).The specimens were sorted from other macroinvertebrates 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.Locus typicus: R. Macedonia, Jablanica Mt., small stream near river Belichka Reka, 41°13'56.7''N, 20°31'27.0''E, 1866 m alt.
Etymology: Named after Prof. Dr Ljupčo Melovski, in appreciation of his significant contribution for nature conservation in R. Macedonia.

Description
Shell.Shell greyish and fragile, cylindrical with 4.5 slightly convex whorls with a moderately deep suture.The first two whorls small in height, the other whorls are fast growing.Apex obtuse, umbilicus closed.Aperture oval, angled at its top.Shell height 2.4-2.7 mm, width 1.4-1.6 mm, aperture height to shell height ratio 0.44-0.47.Soft body.Mantel black with a white border, head dark with a whitish neck, tentacles light with eye spots visible.Morphology of the penis.Penis shorter than penial appendix, flagellum long and regularly thick, translucent.

Habitat and ecology:
The new species inhabits small, shallow and slow flowing streams created by the surplus water draining from the mire complex.Snails were found on hard substrates at 1866 m altitude.Distribution: R. Macedonia, known only known from the type locality (Fig. 6).
mm in B. melovskii (measurements of B. d. drimica after Radoman 1983).The umbilicus in B. d. drimica is slit-like, closed in B. melovskii n. sp., and the aperture is in B. d. drimica not angled.The anatomy and penis morphology of B. drimica is unknown.From B. slaveyae it differs in size (shell height of B. slaveyae 2.3 mm vs. 2.7 mm in B. melovskii n. sp.) and the tubular gland which is not regularly thick but thickened distally.