Surface architecture of the olfactory epithelium of two Chinese cave loaches (Cypriniformes: Nemacheilidae:Oreonectes)

The surface of the olfactory epithelium of two species of cave loaches in China, Oreonectes polystigmus and O. guananensis, was studied by scanning electron microscopy (SEM). The structure of the olfactory organ of the two species is quite different from each other; as well, the distribution patterns of cell types in the olfactory epithelium of the studied species showed interesting features. A needle-like spine is visible on the lamellae of the olfactory organ of O. polystigmus, which is a unique character in this species. Ciliated non-sensory cells and microvillus sensory cells showed a different distribution in the two species, being more numerous in O. polystigmus. The non-sensory elements in O. guananensis were ciliated non-sensory cells, with microridges and chloride cells. The presence of chloride cells in the olfactory epithelium of O. guananensis may be of special interest in this species; otherwise, possible differences and physiological changes of the concerned species should be taken into account in order to explain such variability in cell types.