The Black Nerite Theodoxus prevostianus (C. Pfeiffer, 1828) is a freshwater species which inhabits thermal springs and the initial section of their outflows.
It has a highly patchy distribution in the Pannonian Basin. It is still present in a spring in Bad Vöslau, Austria, the so-called Hansybach. The brooklet which now runs in a kind of channel is surely a negative example of a „natural“ biotope.
The prevostianus went extinct due to reconstruction works or capturing of springs at many places. Today it is listed as „endangered“ in the red list.
(Pictured specimen from the LDK molluscan collection, 7,8 mm, dead collected.)