Morphology of the Inner Ear in Mammals with Different Ecological Peculiarities in Ontogeny
The inner ear is the first to form, as the core, phylogenetically most ancient formation of the peripheral auditory system both in phylogenesis and in ontogenesis. As the development of the inner ear continues, the other parts of the peripheral auditory system of different evolutionary age start to be formed, and the outer ear is the evolutionary youngest among them. All parts of the peripheral auditory system are multicomponent formations. As opposed to the outer and middle ears, which are characterized by different structural variations and a wide spectrum of adaptable transformations connected with the peculiarities of species ecology, the inner ear possesses a variety of functions in the repre-sentatives of different ecological groups and, therefore, keeps a similar structural organization. Usually, both in the cochlear and vestibular analyzers the topography, form and size of separate components vary. Basically, the anatomic formation of the structures of the inner ear finishes in the early prefetal period, while the cellular differentiation of the sensory epithelium of the cochlea, maculas and cristae in immature-born species continues up to the early stages of postnatal ontogenesis. In mature-born species (cetaceans, ungulates), the differentiation of the inner ear structures is complete by the moment of birth.