Histological characterization of the olfactory organ in schilbid catfish, Clupisoma garua (Hamilton, 1822)

Fishes have a good sense of smell and are able to ascertain odour with the help of a pair of olfactory organs connected to the olfactory lobes of the forebrain by means of olfactory tracts. The functional anatomy and structural characterization of olfactory organ in the freshwater Indian Catfish Clupisoma garua (Hamilton, 1822) was investigated by light microscopy. The paired well-developed olfactory organs were located in nasal cavity having two exterior apertures: incurrent and excurrent nares. The olfactory rosettes were elongated structure, possessed 40±02 lamellae on each side of the narrow median raphe. Histologically, each lamella consisted of two principal layers: an epithelium consisted of sensory and non-sensory cells and a central core, which was composed of connective tissues, nerve fibers and blood vessels. The sensory epithelium was composed of three types of receptor cells: two described as classical bearing cilia or microvilli and third bearing rod like dendritic terminal. Synapses between primary and secondary neurons were formed. The indifferent epithelium comprised the greater surface area of the olfactory lamella, was typified with ciliated non-sensory cells, secretory mucous cells, mast cells and supporting cells. Undifferentiated basal cells were scattered in the deeper part of the epithelium above the basement membrane. Organization of various cells on the olfactory epithelium was correlated with essential life process of the fish concerned.