Numerical variation of teeth in the wild house musk shrew Suncus murinus captured from Nagasaki, Japan

Wild populations of Suncus murinus from Nagasaki were thought to be extinct, although specimens from Nagasaki are kept at the National Science Museum, Tokyo. Variation in the number of teeth, including both congenital and postnatal absence, was observed in 25 of 85 individuals. All 25 abnormal individuals were checked using a micro-CT unit to document the presence or absence of embedded teeth and any traits of postnatal absence. Four of these had congenitally absent teeth, whereas the rest showed signs of postnatal absence. There was no significant difference in the ratio of length of tooth group P4M3 against palatal length between individuals with congenital absent teeth and normal ones. Because S. murinus in captivity shows a high rate of periodontal disease, we suggest that the high rate of postnatal absence of teeth in the wild population is due to oral diseases such as periodontal disease or other traumatic factors.