[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.