The histology and surface morphology of the olfactory organ in Silond catfish, Silonia silondia (Hamilton, 1822)

Histological and scanning electron microscopy techniques were employed to study the olfactory organ of Silonia silondia (Siluriformes: Schilbeidae). The thorough examination revealed a well-developed olfactory organ characterized by a series of intricately arranged lamellae that were elegantly inserted into a narrow midline raphe, forming an elongated rosette structure. It comprised the olfactory lamellae, adorned with olfactory epithelium and a distinct median raphe. On each lamella, sensory and nonsensory epithelium were distinctly segregated. The dorsal lamellar processes housed the sensory area, while the nonsensory area enveloped the remainder of the olfactory lamellae. Histologically, each lamella exhibited a central lamellar space, enveloped on either side by olfactory epithelium characterized by receptor cells, supporting cells, lymphatic cells, mast cells, mucous cells, and basal cells. The sensory epithelium contained three morphologically distinct receptor cells: ciliated, microvillous, and rod types. The cellular organization of the olfactory lining was explored in conjunction with the chemosensory system of the fish under investigation.