[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.

[Determination of the physiological age of alive Ixodidae ticks]. / Opredeleniie fiziologicheskogo vozrasta zhivykh iksodovykh kleshchei.

A method has been developed for lifetime determination of the physiological age of hungry imagoes on Ixodes and Dermacentor ticks of natural populations. The procedure has been used to study an alive tick in the liquid (water, physiological saline) against the light background. In doing so, some previously described anatomic and age-specific signs of Ixodes are imaged outwards and their overall age-specific signs are employed. The author has proposed the following criteria for determination of the age of ticks: appearance: 1) the body's thickness; 2) the wrinkles and colour of the cuticle, and the combined sign; 3) transcuticular visibility of the viscera. The last sign was earlier found [8, 9], which is basic in the new method. There is a significant generic specificity of its manifestation. Tables have been constructed for determining four main physiological ages (I-IV) of ticks of both genera. The method has been applied to the study of natural populations of I. persulcatus, D. reticulatus and D. marginatus in combination with virological studies. The method developed allows one to proceed to make a mass determination of the physiological age of alive ticks and basically expands the potentialities of its application.

[The activity of Dermacentor reticulatus Fabr. (Ixodidae) ticks in nature]. / Aktivnost' kleshchei Dermacentor reticulatus Fabr. (Ixodidae) v prirode.

The experimental population-based ecological parameters most closely associated with the age of ticks, including activity, were assessed in the D. reticulatus imago (Moscow Province). The activity rise of ticks in autumn is twice as low as that in spring, with their inactivity in summer. There are some seasonal variations in the ratio of males to females. Evidence has been first provided for the maximum duration (more than 2.5 years, about 1%) of active life till the third spring when the coloured imagoes are let free. Most new-generation individuals have been found to be inactive in autumn. There is a high repeated activity in ticks by seasons: as many as half of the spring individuals (48%) in autumn and more than a third (37%) in spring to come. The repeatedly active individuals whose age is less than a year are most among those in the autumn peak. The summer inactivity of hungry imagoes represents ticks' stable behavioral adaptation, by increasing their active life. This condition is regarded as a component of the "activation diapause" phenomenon.

[The age-related structure of an Ixodes ricinus population studied by using a rapid anatomical method]. / Vozrastnaia struktura populiatsii Ixodes ricinus, izuchennaia s primeneniem anatomicheskogo ékspress-metoda.

A rapid anatomic method for the assessment of the physiologic age of ticks and their virtual age was used in studies of the age structure of a natural population of I. ricinus in the Moscow region. The anatomic method was found quite fit for the purpose. The findings evidence that the age structure of I. ricinus (active imago) population is heterogeneous with variously directed seasonal fluctuations. In spring the structure is the youngest (up to 60% of imagoes are in the second age, 8 months) and in the fall the females are mainly old, just starting to get younger (up to 90% are in the third and fourth ages, that is, aged a year). The structure is liable to changes with seasons and years. Geographic differences in the age structures were revealed: in the fall the Moscow region population is generally older than that of the St. Petersburg region. The anatomic method widens the potentialities of studying the age structure of the populations of tick-borne encephalitis vectors.

[The effect of the physiological age of Dermacentor marginatus (Ixodidae) ticks on their infection with and the infiltration of the tick-borne encephalitis virus into the saliva]. / Vliianie fiziologicheskogo vozrasta kleshchei Dermacentor marginatus (Ixodidae) na ikh zarazhenie i proniknovenie virusa kleshchevogo éntsefalita v sliunu.

The decisive effect of physiological age of ticks on the infection of their saliva was revealed by means of parenteral infection of D. marginatus females with tick-borne encephalitis virus. The virus was not found in the saliva of young individuals of instar II. Maximum number of cases of saliva infection was recorded in mature ticks of instar III (50%). It was established that the infection of saliva did not depend on the amount of virus in the tick's body. Less susceptibility to the virus of young individuals, associated probably with the way of infection, was noted. Under light microscopy there were observed no significant age differences in salivary glands of ticks of instars II and III. The infection of saliva of young individuals is, apparently, opposed by the barrier of fat body on the way of virus to salivary glands, depending on the age of ticks. The barrier is supposed to have an influence under natural transphase infection of ticks.

[Detection of an increase in the proportion of tick-borne encephalitis virus-infected Dermacentor marginatus Sulz. among active females of older physiological ages]. / Obnaruzhenie uvelicheniia doli zarazhennykh virusom kleshchevogo Tentsefalita Dermacentor marginatus Sulz. sredi aktivnykh samok starshikh fiziologicheskikh vozrastov.

Numbers of active females of Dermacentor marginatus ticks infected parenterally with tick-borne encephalitis virus are compared. Increase in this proportion is demonstrated with ticks' physiological aging. Epidemiological and epizootic importance of the discovered phenomenon are the increase in the probability of persistent virus circulation throughout the season, since only active individuals are capable of virus transmission. Besides, it is among them that the virus is most frequently found in saliva.

[Concept of the "physiological age" of animals and its application to ixodid ticks]. / O ponitaii "fiziologicheskii vozrast" zhivotnykh i ego primenenie dlia iksodovykh kleshchei.

The definition "physiological age" of animals has been revised. A new definition has been formulated on the basis of V. N. Beklemishev's (1962) and Ju. S. Balashov's (1962) theses as follows: physiological age of animals (= biological) is an extent of general irreversible morphophysiological change of organism during its whole life and determined by the accumulation of irreversible changes as a result of its normal vital activity. This definition is equivalent to that of "biological ages" of man. The contents of this definition is enlarged and the possibility of its use for different animals including their males is unified. On the basis of the general concept this definition is specified in regard to ixodid ticks: physiological age of hungry ixodid tick is an extent of general irreversible morpholophysiological change of its organism during the whole life and determined by the state of reserve nutrient and excretory substances. According to the amount of reserve and excretory substances in the organism of ixodid tick we distinguish 4 main physiological ages: new-born, young, mature and old which reflect general biological regularity of age development of animals.

[Improved method for the histological determination of the physiological age of ixodid ticks (Ixodidae)]. / Usovershenstvovannyi metod gistologicheskogo opredeleniia fiziologicheskogo vozrasta iksodovykh kleshchei (Ixodidae).

Hystological study of hungary imagos of Dermacentor pictus Herm. and other ticks of the genus Ixodes has made it possible to improve the method of physiological age determination of ixodids (Balashov, 1961). The following criteria for age determination are suggested: 1) size of sections of midgut appendages and their structural peculiarities, 2) height of midgut epithelium, 3) amount of haemoglobin inclusions in midgut cells, 4) amount of haematin in midgut cells, 5) cellular structure of midgut epithelium. Four main physiological ages can be determined by means of the above method (Razumova, 1977), which correspond to four degrees of nourishing according to Balashov (1961). By means of the method a stereotype of seasonal changes in the age structure of C. pictus population has been found out--a younger composition in spring and old one in autumn.

[Cell structure of the intestinal epithelium as an index of the physiological age of ixodid ticks (Ixodidae)]. / Kletochnoe stroenie kishenchogo épiteliia kak pokazatel' fiziologicheskogo vozrasta iksodovykh kleshchei (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.