[Effects of thyroid hormone level alterations on the Weberian apparatus ontogeny of cyprinids (Cyprinidae; Teleostei)].

Effects of thyroid hormone (TH) level alterations on the development and definitive morphology of the Weberian apparatus (WA, morphofunctional complex, providing transmission of sound signals from the gas bladder to the labyrinth of inner ear) were experimentally assessed in cyprinid fishes (Labeobarbus intermedius and Danio rerio). Alterations of TH-level were shown to lead to heterochronies, changes of timing and rates of ontogenetic events resulting in changes of definitive morphology of some structures as well as of the WA as a whole. Differences, in reaction of WA structures to the TH-level alterations, and inter- and intraspecific variability of TH-responsiveness were revealed.

[The role of the thyroid gland hormone in ontogenesis and morphological diversification of Barbus intermedius sensu of Lake Tana in Ethiopia].

The role of thyroid gland hormone in the ontogenesis of the Large African Barb Barbus intermedius sensu Banister, 1973 (Teleostei; Cyprinidae)--the supposed ancestral species which produced the species flock of the large African Barbs of the Lake Tana (Ethiopia)--has been studied. It has been shown that the thyroid hormone influences the period of many morphological processes and a change in its level causes heterochrony, reflecting on the definitive morphology of fish. Thus, it can be assumed that even a slight change in activity of the thyroid axis in the process of ontogenesis can be the cause of wide variability of the morphological features of B. intermedius and is at the basis for the fast diversification of the species flock of Big African Barbs of Lake Tana.

[Ontogenesis and population: evaluation of developmental stability in natural populations]. / Ontogenez i populiatsiia:otsenka stabil'nosti razvitiia v prirodnykh populiatsiiakh.

Ontogenetic and population studies traditionally develop independently. At the same time, the relevance of specific analysis of a specimen as ontogenesis for both correct assessment of populations and their dynamics in time and space and understanding the mechanisms underlying population processes is becoming more and more clear. Developmental stability serves as the most general description of the developing organism status. The level of developmental noise commonly evaluated by fluctuating asymmetry is the main index of developmental stability. High developmental stability is maintained on the basis of genetic coadaptation under optimal developmental conditions. Coordinated changes in developmental stability and other homeostatic indices, including genetic, physiological, biochemical, and immune indices suggest that we consider the general status of the organism by evaluating its developmental stability. Evaluation of developmental stability as a measure of environmental stress, apparently, is the most promising. In practical terms, this allows us to evaluate and monitor environmental health under both natural and various anthropogenic conditions. Outlooks of this approach as relates to studies of developmental stability are discussed.