Redescription of Pleuretra hystrix, an endemic alpine bdelloid rotifer

Pleuretra hystrix Bartoš, 1950 is a peculiar bdelloid rotifer unrecorded for more than 50 years since its description. We found this species in the western Italian Alps and we redescribe it, confirming the validity of this species. New morphological details are described from scanning electron micrographs. Variability in spines on the trunk is great; their adaptative significance in bdelloid rotifers is discussed.