The Influence of Fixatives on the Validity of Histological Preparations of Olfactory Organ in Teleostei

Abstract

The olfactory system of fishes plays an important role in reproduction, migration, and feeding. When studying the morphogenesis of olfactory analyzer in fishes, it is crucial to determine the exact time at which the placode, olfactory pit, and olfactory lamellae are formed. Among a large number of fixatives, 10 % formalin and Bouin’s solution are most commonly used to study the olfactory organ of Teleostei. Use of inappropriate fixative or incorrect fixation process can damage the structures under investigation and, as a result, will lead to the misinterpretation of results. The influence of the fixatives on the preservation of olfactory structures of European weather fish Misgurnus fossilis (Linnaeus, 1758) as close as possible to their living state is studied. Similar stages were fixated in Bouin’s solution as well as in 10 % formalin. Histological preparations for the light microscopy were made using the standard histological methodologies. At all analyzed stages of European weather fish development, histological preparations are more accurate, reliable, and informative aft er the fixation in Bouin’s solution. Aft er the fixation in 10 % formalin, it is impossible to determine the moment at which the olfactory pit begins to form. Because of the artifacts of olfactory epithelium appearing aft er fixation in 10 % formalin, the timing of olfactory lamellae formation could be easily misinterpreted and a comparative analysis on the morphogenesis of the olfactory analyzer becomes more complicated. Given our observations, a thorough revision of previous literature has to be performed to derive accurate evolutionary and morphological interpretations.