The olfactory organ of schilbid catfish Eutropiichthys vacha (Hamilton, 1822): morphological and ultrastructural studies

Abstract

Abstract Background A study of the olfactory organ structure in freshwater catfish, Eutropiichthys vacha, was carried out to explore the cellular constituents by aid of light as well as scanning and transmission electron microscopy. Results The paired elongated olfactory organs were situated on the dorsolateral facet of the head in the mold of simple pits. The olfactory organ was made up of a series of leaflets, the lamellae, which embedded into both sideways of slender central raphe, forming a rosette distinguished with sensory and nonsensory areas. The sensory receptor cells were present on sideward surface and linguiform process of olfactory lamella while the rest of the portion of the lamella was lined with nonsensory epithelium. Olfactory cells were characterized by their staining intensity, outline, surface features, and comprehensive morphology in the epithelium. The sensory mucosa was defined by the occurrence of three types of neuron: classic types bearing either cilia or numerous microvilli and third type having rod-shaped architecture. The nonsensory epithelium was composed of mucous cells, labyrinth cells, mast cells, and two types of supporting cells categorized as ciliated or nonciliated. Basal cells lie deep in the olfactory lining, near the central core. Conclusion The structural components of the olfactory apparatus crucial for olfaction were correlated with the behavioral activities of fish.