The genus Microtus comprises more than 60 herbivorous rodent species that possess a compound stomach specialized for microbial fermentation. Although fimbriae at the esophageal–glandular junction and the pyloric gland region are considered characteristic features of the genus, detailed comparative descriptions remain limited. We examined the gross and histological stomach morphology of five Microtus species representing several phylogenetically distinct lineages (M. arvalis, M. levis, M. guentheri, M. montebelli, and M. ochrogaster). All species shared a three-part compound stomach, an esophageal groove–like structure, fimbriae, ridge-like projections near the pyloric orifice, and a pyloric gland region consistently located on the duodenal side of the pylorus. Meanwhile, fimbrial morphology showed substantial interspecific and individual variation in shape, size, and arrangement. These findings indicate that the basic stomach architecture is conserved across Microtus, whereas variation in fimbriae may reflect species-specific adaptations or environmental influences. This study provides an initial comparative analysis of stomach morphology across multiple Microtus lineages and contributes to understanding the evolutionary diversity of digestive traits within this herbivorous genus.
