Structural observations on the gills of two fresh water teleost fishes, Notopterus notopterus and Colisa fasciatus.

1. The structural observations of the gills of Notopterus and Colisa fasciatus have been studied in detail. 2. The gills of Notopterus notopterus and Colisa fasciatus consist of 2 regions: a) Gill head region, and b) Gill lamellae region. Gill head region is covered by epithelial layer possessing the mucous and mast cells. Gill head region consists of bony arch, gill rakers and interbranchial septum. 3. Interbranchial septum is reduced in Notopterus notopterus while it extends near half to the length of the filament in Colisa fasciatus. 4. In both fishes, the adductor muscle, afferent and efferent branchial vessels and gill rays are present in the interbranchial septum area. 5. Gill lamellae region consists of primary and secondary lamellae in both the fishes. 6. In Notopterus notopterus the primary lamellae are compressed flat structures possessing gill rays, 1 afferent and 1 efferent branchial vessel, while in Colisa fasciatus 2 efferent vessels are present. 7. Secondary lamellae are arranged parallel to one another on both sides of the primary lamellae. Secondary lamellae consist of basement membrane, epithelial cells, vascular layer and pillar cells. Mucous and mast cells are also present in this region in case of Notopterus notopterus while only mast cells are present in Colisa fasciatus. 8. Mast cells are eosinophilic, highly granulated in both the fishes.