Five new species of Radomaniola Szarowska, 2006 (Truncatelloidea: Hydrobiidae)

The genus Radomaniola Szarowska, 2006 (Horatiinae) groups minute gastropods inhabiting mostly springs, but also streams, rivers and subterranean waters in the Balkans, and which are widely spread in the former Yugoslavia, but were recorded also from Italy and Greece. Thirty-six valid species distinguished so far still represent only a part of the real biodiversity within the genus. Wide morphological variability forces the application of molecular characters in the taxonomy of the genus. Cytochrome c oxidase subunit I (COI) is the most widely used marker, appropriate for genus level identification, but not sufficient for the reconstruction of deeper nodes in the phylogeny. Our materials were collected for more than 20 years: from 2001 to 2022, at 101 localities in Croatia, Bosnia and Herzegovina, Montenegro, Albania, and Greece, with 67 of them not previously studied. Many COI haplotypes have not been recorded previously. In the present paper we describe five molecularly well supported species new to science, found at 21 localities in Croatia, Bosnia and Herzegovina, and Greece, considering both morphological and molecular (COI) data. The shells, female reproductive organs and penes are described and illustrated. Wide intraspecies variability, coupled with slight differences between the taxa, were observed in the shells, penes, and female reproductive organs, suggesting morphostatic evolution in the genus Radomaniola.