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

Records of <i>Sarcocystis</i> 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 <i>Sarcocystis arvalis</i> n. sp. from the common vole (<i>Microtus arvalis</i>). 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 <i>18S</i> rRNA, <i>28S</i> rRNA, <i>cox1</i> and <i>rpoB</i> loci, <i>S</i>. <i>arvalis</i> n. sp. showed the highest similarity with <i>Sarcocystis myodes</i> from the bank vole (<i>Clethronomys glareolus</i>). According to the phylogenetic placement, <i>S</i>. <i>arvalis</i> n. sp. is the most closely related to <i>Sarcocystis</i> spp. with a rodent-mammal lifecycle. Morphologically, <i>S</i>. <i>arvalis</i> n. sp. forms sarcocysts that share a lot of similarities with those of <i>S</i>. <i>myodes</i>, <i>Sarcocystis ratti</i> and <i>Sarcocystis cernae</i> 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 <i>S</i>. <i>arvalis</i> n. sp. are red foxes, stone martens, least weasels, and domestic cats.