Resolving the identity of an enigmatic cestode of rodents and birds: Hymenolepis murissylvatici (Rudolphi, 1819) transferred to the genus Variolepis Spasskii and Spasskaya, 1954.

Wood mice (Apodemus sylvaticus), yellow-necked mice (A. flavicollis) and voles (Microtus agrestis) from the British Isles and from the European mainland have been reported to carry a cestode referred to as Hymenolepis murissylvatici. However, based on the morphometrics of diagnostic characters, Prokopič (1967) showed that isolates of this species from wood mice were indistinguishable from a species parasitizing a range of birds, which he referred to as Variolepis crenata. Subsequently, Vaucher et al (2003) showed that this was not a valid conclusion. Here, we track the key nomenclature changes associated with isolates from rodents and birds. Following recent revisions of genera in the Hymenolepididae, including the reinstatement of Variolepis as a valid genus, and based on both published morphometric criteria and 28S rDNA sequencing, we conclude that synonymy of H. murissylvatici from rodents with V. crenata from birds is not safe. Instead, we propose that until molecular genetic analyses of isolates from woodpeckers, passerine birds, and rodents have been completed, reference to this species as Variolepis murissylvatici comb. nov. is currently more appropriate and justified by available information. We review studies recording V. murissylvatici in wild rodents, and experiments in which the host-parasite relationship of this cestode was explored in laboratory mice and identify directions for future exploration of the biology of this enigmatic species.