A NEW MONTENEGROSPEUM SPECIES FROM SOUTH CROATIA (MOLLUSCA: GASTROPODA: HYDROBIIDAE)

A bstract: The extremely rich stygobiont malacofauna of the Balkans is still poorly studied, and the systematics is based mostly on shells whose characters are often misleading. An interesting stygobiont gastropod species was found in several springs feeding the Cetina River in the SW. part of Sinj Basin in Croatia. Its shell resembled the ones of moitessieriid genera Paladilhiopsis, Bythiospeum, or Iglica. Analyses of COI and H3 markers placed it close to the hydrobiid Montenegrospeum bogici Pesic et Gloer, 2012 from central Montenegro. It is congeneric but molecularly and morphologically distinct. The new species is described herein as Montenegrospeum sketi n. sp.


INTRODUCTION
The extremely rich stygobiont malacofauna of the Balkans is still poorly known, and the systematics is based m ostly on shells whose characters are often misleading. . Later, applying molecular markers (mitochon drial cytochrome oxidase subunit I, COI and nuclear 18SrDNA), it was shown that Montenegrospeum did not belong to the M oitessieriidae, but to the Hydrobiidae Troschel, 1857, subfamily Sadlerianinae Radoman, 1973, with Dalmatinella Radoman, 1973 as the sis ter taxon (FALNIOWSKI et al. 2014). This was also confirmed by morphological data (FALNIOWSKI et al. 2014): female reproductive organs with two sem i nal receptacles (rsj and rs2: RADOMAN 1973RADOMAN , 1983, and penis with a lobe on the left side o f its median part (PESIć & GLOER 2013), also similar to the ones characteristic o f several genera o f the Sadlerianinae (SZAROWSKA 2006). Recently a few localities were found in Croatia with Montenegrospeum-like empty shells and a few live specimens became available for molecular studies. All those localities represented karst habitats. The aim o f this paper is to establish the systematic position o f the new species, and to describe it as Montenegrospeum sketi n. sp., applying shell morphology and molecular markers.

MATERIAL AND METHODS
The studied material was obtained by sieving sandy sedim ents o f karstic springs using microhab itat preferences and sampling method according to GREGO et al. 2017a (Fig. 1).
Three live specimens were collected at two local ities ( Fig. 1 as a reference (Table 1). The data were analysed using approaches based on the Bayesian inference and m axim um likelihood (ML). We applied the GTR model, whose param eters were estim ated by RaxML (STAMATAKIS 2014). The Bayesian analyses were run using MrBayes v. 3.2.3 (R ONQUIST et al. 2012) with the default priors. The GTR model was best fitted to our data. Two sim ultaneous analyses were performed, each o f which lasted 10,000,000 generations, with one cold chain and three heated chains, starting from random trees and sampling the trees every 1,000 generations. The first 25% o f the trees were discarded as burnin. The analyses were sum m arised as a 50% majority-rule tree. The ML approach w as applied with RAxML v. 8.0.24 (STAMATAKIS 2014). One thousand searches were initiated with starting trees obtained using the randomized stepwise addition maximum parsimony method. The tree with the highest likeli hood score was regarded as the best representation

MOLECULAR PART -RESULTS AND DISCUSSION
The sequences were obtained from two specimens (Figs 6, 7). The saturation tests revealed no satura tion. The ML tree (Fig. 8) (Figs 13, 14), in its more elongated conical shell shape, slightly more inflated whorls, more prominent umbilicus as well as in the different aperture situated more to the right from the columellar axis. The lateral profile o f the lip is more forward protruding at its lower end and more sinuated in M. bogici. The proportionally smaller aperture of the new species is less produced at the lower part o f the shell outline and its margin is less reflected.  The milky white semi-translucent shell has five convex inflated whorls separated by a deep suture. It is elongated-conical with smooth surface and aperture slightly protruding against the body whorl and its left margin not protruding beyond the columellar axis. The aperture is oval, vertically elongated and attached to the body whorl by a tiny furrow; the peristom e slightly outward expanded in some specimens. The umbilicus is tiny and opened.
The lateral profile o f the lip margin very slightly sinuated and alm ost parallel with the columellar axis.  G r e g o J., G lo e r P., E r ó s s Z. P., F e h e r Z. 2017a. Six new subterranean freshwater gastropod species from north ern Albania and some new records from Albania and