Description of Sarcocystis arvalis n. sp. from the Common Vole (Microtus arvalis) in Lithuania Using Morphological and Molecular Methods.

Records of Sarcocystis spp. diversity in rodents are relatively extensive; however, the increasing application of molecular approaches indicates that our current knowledge of these parasites remains incomplete. In the present study, morphological, genetic and phylogenetic data are provided on Sarcocystis arvalis n. sp. from the common vole (Microtus arvalis). Using light microscopy, the observed sarcocysts had a relatively thin (<1 μm) and smooth cyst wall. Via transmission electron microscopy, the sarcocyst wall thickness ranged from 0.7 to 1 μm, and the parasitophorous vacuolar membrane exhibited small knob-like blebs and was slightly wavy, type 1a. Based on 18S rRNA, 28S rRNA, cox1 and rpoB loci, S. arvalis n. sp. showed the highest similarity with Sarcocystis myodes from the bank vole (Clethronomys glareolus). According to the phylogenetic placement, S. arvalis n. sp. is the most closely related to Sarcocystis spp. with a rodent-mammal lifecycle. Morphologically, S. arvalis n. sp. forms sarcocysts that share a lot of similarities with those of S. myodes, Sarcocystis ratti and Sarcocystis cernae and molecular analysis is necessary for accurate species identification. Based on the abundance of the hosts and the proportion of voles in their diet, the most likely definitive hosts of S. arvalis n. sp. are red foxes, stone martens, least weasels, and domestic cats.