Patterns of Adaptational Changes in Leukocytes and Platelets of Yakutian Ground Squirrels during the Pre-Hibernation Period in Autumn

Previously, it has been shown that a series of physiological and biochemical changes occur in Yakutian long-tailed ground squirrels during autumn (the pre-hibernation period), involving the brain, heart, skeletal muscles, and other organs. This study was conducted to analyze the composition of peripheral blood cells obtained from Yakutian ground squirrels in autumn. For the first time, an increase in the total number of leukocytes, particularly granulocytes, and a decrease in the number of lymphocytes were observed when compared with samples obtained in summer; a leukogram shift from the lymphocytic to the granulocytic fraction was revealed. Significant increase in platelet counts and thrombocrit with preservation of the percentage ratio of mature and young cell fractions was shown. To date, information on the cellular components of blood during the autumn season when hibernators prepare for winter months of hibernation remains scarce. Nonetheless, the results of our study indicate that very significant adaptive changes occur in leukocytes and platelets of ground squirrels in this period. Possible causes of these changes are discussed.