Variability of molars in the Кorean field mouse - Apodemus peninsulae (Rodentia, Muridae)

The Korean fi eld mouse (Apodemus (Alsomys) peninsulae) is a widely distributed species – a carrier of especially dangerous infections, such as tick-borne encephalitis virus, borreliosis, etc. The morphometric differentiation of geo-graphical forms is weakly expressed, and the morphological one has not been studied yet. In the present study, it was investigated 296 upper and lower molars from 28 specimens of the Korean fi eld mouse population from the Ussuriysky Nature Reserve of the Primorsky Territory. It was for the fi rst time that the authors described 28 variable and 5 permanent features, fi ve of them being for the fi rst time revealed in the Alsomys subgenus. The greatest variability was found in the fi rst upper and fi rst lower molars, and the least – in the second upper molar. Previously, in the subgenus of Alsomys, vari-ability in the molars morphology was known only for the A. speciosus and A. argenteus species, endemic to the Japanese islands. The three species molars comparison revealed both similar and unique features characteristic of the A. peninsu-lae. This work will give a start to morphological study of the A. peninsulae characteristics dependent on certain environ-mental conditions, and the opportunity to not only describe the unique geographical populations, but also characterize the paleontological material.