Tytiuk O. Morphogenesis of olfactory organ of some teleostei with different trophic specializations

For the first time the development of the olfactory organ of European weatherfish (Misgurnus fossilis) and bushymouth catfish (Ancitrus dolichopterus), from the anlage to its definitive state, was studied. Moreover, olfactory rosettes of species under study weredescribed. New data about morphogenesis and morphology of the olfactory organ of teleostei with different trophic specialization and living conditions was provided. The time of setting up of the olfactory placode and duration of different developmental stages of the olfactory organ were identified. The mechanism of formation of the olfactory pit, the nasal bridge, lamellae and the olfactory epithelium at different stages of ontogenesis was monitored. Tables of the normal development of bushymouth catfish based on its morphological and physiological characteristics are created.Itis found out that at the time the embryo hatches, the olfactory pit of Ancitrus dolichopterus has been already formed, whereas in Misgurnus fossilis it is still at an emerging stage. In Misgurnus fossilis, lamellae appear at the end of the larval stage, while in Ancitrus dolichopterus the olfactory rosette formed with three lamellae appears much earlier. In both Misgurnus fossilis and Ancitrus dolichopterus, the specific mechanism of tubular nostril formation was identified: before the nasal bridge starts being formed, the rostral edge (Misgurnus fossilis) or the whole rostral part (Ancitrus dolichopterus) of the olfactory pit is rising gradually signalling the beginning of the anterior tubular nostril formation, even though the hole of the olfactory pit has not been divided yet. The structure of the olfactory organ of Ancitrus dolichopterus keeps some characteristics of the representatives of the Siluriformes, but the role of the olfaction in searching food is not critical (due to adapting to the alimentation via fouling, thus the permanent access to food). In Misgurnus fossilis, the adaptation of the olfactory organ to the near-bottom mode of life in muddy water reservoirs is vividly observed. Only at the larval developmental stage the olfactory organ plays the crucial role in finding food.