Surface architecture of the opercular epidermis and epithelium lining the inner surface of the operculum of a walking catfish, Clarias batrachus

Abstract

In Clarias batrachus, the opercular epidermis (OE) and epithelium lining the inner surface of the operculum (EISO) showed significant differences in their surface architecture, such being correlated with different conditions at the two locations. The surfaces of the epithelial cells had characteristically intricate patterns of microridges, which were mostly short-ridged with narrow spaces between them (OE) or high-ridged and widely spaced (EISO). These patterns were believed to be associated with the relative extent of surface secretory vesicles, present for the secretion and renewal of the extracellular cuticular coat at these locations. Extensively distributed on the OE, wide mucous cell openings enable increased mucus secretion, considered to be an adaptation resulting from the greater need for lubrication, protection and inhibition of invasion and proliferation of pathogenic microorganisms, than at the EISO, where mucous cell apertures were few and narrow. Taste buds were generally situated at papillate, epidermal elevations that projected from the OE surface. This possibly enhances gustatory function, being an adaptation compensating for reduced vision. The absence of taste buds in the EISO suggested that a gustatory function does not occur in that region.