New Type of Development of Olfactory Rosette of Bushymouth Catfish Ancistrus Dolichopterus

Abstract

Depending on the living conditions, sensory systems of fishes, namely the olfactory analyzer, are developed differently. The form of olfactory rosette and morphology of olfactory lamellae affect the ability of fish to perceive an odorant. It is considered that the longitudinal bilateral olfactory rosette is typical for those species that have a well-developed olfaction. As a rule, olfactory rosettes with similar morphology are typical for species belonging to close families or living in similar environments. The olfactory organ of fish during its development goes through such developmental stages as olfactory placode, olfactory pit, and olfactory chamber with olfactory rosette. However, the mechanism of development of olfactory rosettes remains unclear. There was not enough attention paid to the particularities of formation of central raph in olfactory rosettes, as well as to the appearance of new lamellae in different species of teleosts. For studying the development of the bilateral olfactory rosette, bushymouth catfish Ancistrus dolichopterus were cultivated in the laboratory of histology and morphogenesis of Lesya Ukrainka Eastern European National University. Histological preparations were accomplished according to standard histological methodologies. In Ancistrus dolichopterus, formation of olfactory rosette goes in four stages. At the first stage, the first lamella appears in the central part of olfactory chamber and becomes elongated to its rostral wall. At the second stage, first lateral and medial lamellae begin to form. At the third stage, the fourth lamella appears from the medial side of the central raph. At the fourth stage, at first, the addition of lamellae takes place, symmetrical to the central raph. Then, when it comes to new paired lamellae, the lateral lamellae are more rostral than the medial ones. In Ancistrus dolichopterus, the central raph develops from the first central lamella, which elongates with the increase in length of the olfactory chamber. The thickening of the raph is possible through the attaching of new pairs of olfactory lamellae to it, in the rostral part of olfactory chamber. During the development, the distal end of the central lamella moves laterally and loses its axial position. Bilateral olfactory rosette of Ancistrus dolichopterus gets its definitive state because of addition of new lamellae, more rostral that lamellae already formed, as it happens in most teleosts, even with other types of olfactory rosettes. During the formation of the fourth lamella, the symmetry is broken, as lamellae are being formed only from the one side of the central raph. All the following lamellae are formed in pairs.