Interspecific variation of hibernation marks in incisor dentin of rodents

摘要

Cross sections of upper incisors form 66 overwintered individuals of 17 species of Sciuridae, Myoxidae, Allactagidae, Dipodidae, Critecidae collected in May-July were analyzed to reveal a specific mark of hibernation in incisor dentin of rodents (zone of hibernation). Three types of records of the winter season were found in the dentin: (I) a series of contrasting hyper- and hypochromatic layers decreasing in width (Spermophilus, Marmota, Mesocricetus); (II) a single contrasting hyper- and hypochromatic band including several narrow faintly stained layers (Muscardinus, Dryomys, Myomimus, Glis, Pygerethmus, Allactaga, Dipus); this type was similar to that previously described in Sicista (Sminthidae); (III) a series of normally stained layers decreasing in width (Tamias). The formation of the zone of type I is related to periodical renewal of dentinogenesis during spontaneous enthermic episodes in the course of dormacy. The formation of the zone of type II reflects a strong retardation of dentinogenesis during hibernation. Type III may be a record of the rodents' winter activity.