[Physiological, biological age in case of ixodid ticks]

The definition concept of the "physiological age" of animals has been revised on the basis of studies of ixodid ticks. The physiological age of animals is considered to be a general biological notion and to be equal to the notion of "biological age" of human beings. The notion "physiological, biological age" expresses gradual irreversible biological changes in an organism during its life. Thus, this is a level of biological ageing of an organism. The main feature of the notion "biological age" is the irreversibility of biological changes associated with normal vital functions of the body. The real changes in the body during its life are estimated by the alterations that are characterized by normal vital functions. These features correspond with the biological index "a life part that has passed". Based on these features, a general notion "physiological, biological age" is formulated, which is also applied to ixodid ticks.