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Histological Organization And Ultr-Structures Of The Apical Surface Of The Olfactory Epithelium Of A Carp, Labeo Bata (Hamilton)

Ishita Samajdar and Dipak Kumar Mandal*

The olfactory organ being a major chemoreceptor organ in fish plays a significant role in searching food and mate, predator avoidance and reproduction. Structural organization of the olfactory shows variations among different fishes due to their adaptation to various habits and habitats. This study investigates the histological organization, histocheical nature and ultrastructures (SEM study) of the olfactory organ of Labeo bata (Hamilton). The peripheral end of the organ, olfactory rosette comprising 46-48 lamellae is provided with a large surface area of neurosensory epithelium and is placed on the floor of each nasal chamber. The organ communicates to the external environment through inlet and outlet openings of nasal aperture separated by a concave skin flap which facilitates water flow through nasal chamber. Two layered epithelium covering each lamella consists of sensory and non-sensory cells. Sensory cells cover lateral sides while non-sensory cells cover median ridge and outer edges of lamella. Sensory epithelium possesses both of the ciliated and microvillous olfactory receptor cells (cORC and mORC) along with supporting cells, basal cells and ciliated non-sensory cells. Histochemical localization revealed that mucous cells contain acidic and neutral mucin and distributed throughout the epithelium. Scanning Electron Microscopic (SEM) observations disclosed that the narrow dendrite ends of ORCs possess either 5-6 cilia or many microvilli on their apical surfaces. Broad apical surfaces of stratified non-sensory cells are provided with microridges. Functional significance of the different olfactory epithelial cells and fine structures on their apical surfaces are discussed. This study reveals that the olfactory organ of L. bata is well organized and seems to be efficient.