The record of the reproductive cycle in the incisor dentine of spotted souslik Spermophilus suslicus

To examine the changes in dentine microstructure in spotted souslik Spermophilus suslicus (Giildenstaedt, 1770) during pregnancy, parturition and lactation, we investi­gated 39 females from the Odessa region. Thirty females were dead-trapped in March­-July, 1987-1997, nine females (lactating or pregnant) were caught in April, 1996, injected with tetracycline as a time marker and kept in captivity during 14-47 days. Their litters survived from 1 to 29 days. We analyzed cross stained sections as well as cross ground sections of upper incisors. In the lactating sousliks both in nature and in captivity the daily layers formed in the course of pregnancy were followed by formation of a specific dentine pattern. The pattern consisted of alternating contrastive hypo- chromatic and hyperchromatic bands of about 30-50 n wide. The beginning of the pattern formation coincided approximately with parturition and the formation con­tinued during lactation. Therefore, the parturition-lactation zone could be the correct name for the pattern. In captured females no correlation between the duration of the pattern formation and the lifespan of their litters was found. The pattern was absent in immature and barren females. We found no changes in the dentine formation during pregnancy.