SEM surface structure of the adhesive organ of the hillstream fish Glyptothorax pectinopterus (Teleostei: Sisoridae) from the Garhwal Hills.

Glyptothorax pectinopterus has a well defined bilateral adhesive organ situated posteriorly to the mouth, between the opercular opening and the base of the pectoral fin. It narrows at its anterior and posterior end and is characterized by thin longitudinal ridges and grooves running almost parallel to the main body axis, but with a slight inclination posteriorly. The ridges all seem to converge towards the posteriorly localized middle pad. In conformity with the hillstream type of habitat, the ridges are surmounted by long, keratinized epidermal spines with hooked, curved or sucker-like tips. The hooked spines, in adhesion to the substratum, attach themselves firmly to organic material, while the sucker-tipped spines reinforce adhesion by generating vacua at innumerable scattered points. The effect of mechanical abrasion of the spines is minimized by a glandular secretion from the middle pad.