[Cell structure of the intestinal epithelium as an index of the physiological age of ixodid ticks (Ixodidae)].

As hystological studies of hungry image of Dermacentor pictus Herm. have shown changes in the cellular structure of the midgut epithelium and the decrease in its height (about 3 times) can serve as indicators of physiological age of the ticks. The structure transformation manifests itself in regular changes of the cells content of the midgut epithelium and numerical ratio between midgut cells of various types of different age. In new-born and young individuals digestive cells with haemoglobin dominate, new-born ticks are characterized as well by brown digestive cells. Epithelium of adult ticks consists of secretory and reserve cells, that of old individuals-mainly of reserve cells, specialized in accumulation of hematin, and rare secretory ones. Digestive and secretory cells are regarded as morphologically differing consequitive stages of the development of one kind of cells while secretory cells are considered to be their mature stage ready for feeding of an individual. It is assumed that in hungry ticks there are periods of more and less rediness for feeding while in adult ticks the best rediness for feeding is obseved. Maximum development of secretory cells in midgut epithelium is the main indicator of mature age (IIIrd physiological) of hungry ticks.