A histochemical study of the epidermis of the climbing perch, Anabas testudineus (anabantidae, pisces)

Abstract

A histochemical investigation has been made to localize and characterize various lipid, protein, carbohydrate and enzyme constituents present within the different cell types of the epidermis of Anabas testudineus. The polygonal cells contain glycogen, the amount of which gradually increases as the cells move towards the surface until they reach the most superficial layer where the amount of glycogen slightly decreases indicating the metabolically active state of these cells. The basal cells, which frequently undergo cell proliferation, contain no glycogen. The polygonal cells give strong reactions for SDH, alkaline phosphatase, cholesterol esters and nonsulphated acid mucopolysaccharides, moderate reactions for acidic lipids, phospholipids and free cholesterol and weak reactions for neutral mucopolysaccharides, protein bound NH2 groups, mucoprotein, tyrosine, tryptophan and cysteine bound sulphydryl groups. These cells in the outermost layer give stronger reactions for acidic lipids, phospholipids and cholesterol esters and weaker reactions for SDH and alkaline phosphatase activities. The above findings reveal that the polygonal cells remain metabolically active throughout the epidermis. The mucus cells are numerous and secrete a mixture of neutral mucopolysaccharides, sulphated acid mucopolysaccharides and nonsulphated acid mucopolysaccharides. The contents of the sacciform granulated cells are mainly proteins. A thick coat of slime over the body surface containing mucopolysaccharides, lipids and proteins is important in keeping the skin moist and may facilitate the survival of the fish while it is on land. The melanophores in the epidermis play an important role in preventing the colonization by parasites, fungi and bacteria over the body surface, and act as macrophages.