[New phreatic and stygobitic hydrobiids from the Northern Apennines in Piedmont, Liguria and Emilia-Romagna (Gastropoda: Caenogastropoda: Hydrobiidae)]

Five new species of phreatic and stygobitic hydrobiids are here described for the Ligurian-Piedmontese and Emilian Apennines. Two species belong to the genus Alzoniella: Alzoniella borberensis n. sp., endemic to the sub-basin of the Borbera and Spinti streams, and to the lower stretch of the Scrivia stream, in the province of Alessandria, and Alzoniella isoensis n. sp., limited to the middle course of the Scrivia stream and to the basin of the Polcevera stream, on the Tyrrhenian sector of the Genoa province. Three species belong to the genus Fissuria: Fissuria globosa n. sp., widespread throughout the sub-basin of the Scrivia stream (Genoa and Alessandria provinces), as well as in other Apennine watercourses of the provinces of Alessandria, Piacenza, Parma and Reggio Emilia; Fissuria varicosa n. sp., present in the same area of Alzoniella borberensis n. sp., but also found in the Nure and Arda streams (Piacenza province) and in the Stirone stream (Parma province), and Fissuria sossoi n. sp., limited to the sub-basin of the Stura di Ovada streams (Genoa province).The first species, assigned to the genus Alzoniella Giusti & Bodon 1984 based on its anatomical characters, has a shell with peristome detached from the last whorl, such as that of other phreatic species already known for eastern Liguria and central Italy, but differs from these in the shorter shell. The shape of the shell of A. borberensis n. sp. resembles that of other crenal or stygobitic species, widespread in northern Italy. A. isoensis n. sp., is very similar to A. borberensis, although the peristome is not sinuous superiorly on the outer edge of the shell, but differs sharply in the anatomical characters. The other taxa with valvatoid shells here described, can be ascribed to the genus Fissuria Boeters 1981 based on their anatomical characters, and show some peculiarities of the male genital tract that distinguish them from the other congeneric species so far known for southern Europe. The three new species of Fissuria differ mainly in the characters of the shell, more or less globose in F. globosa n. sp., more conical in F. sossoi n. sp. and more flattened in F. varicosa n. sp.; the latter is also characterized by the presence of a marked varix behind the peristome. Altogether, these new species can be defined as phreatic, as they colonize groundwater near watercourses; only A. isoensis n. sp. has a wider ecology, as it also lives in karst groundwater and groundwater in rocks permeable by fracking. The groundwater in contact with the watercourses hosts a taxocenosis composed of stygophile or stygobitic hydrobiids able to colonize different habitats, such as springs, karst groundwaters, or aquifers in permeable fractured rocks, but they also host very specialized taxa often limited to very restricted ranges. The few main biodiversity hotspots are especially distributed in north-eastern Italy, especially in Isonzo basin, in the sub-basin of the Scrivia stream between Liguria and lower Piedmont, in eastern Liguria, in Tuscany and in a few other catchments of southern Italy, in medium-sized watercourses with a suitable substrate. The main ecological, biogeographical and palaeogeographical factors that may have interacted in determining the speciation and the current distribution of this unique population, are then analysed.

[Article in Italian]