Comparative studies on the histological structure of skin in fresh and brackish water fish

Abstract

Objective: To characterize and compare the skin structure of fresh and brackish water fish. Design: Descriptive study. Animals: Two types of brackish water fish were used: sea bass (Dicentrarchus labrax) and grey mullet (Mugil cephalus) and two types of freshwater fish were used: catfish (Clarias lazera) and common carp fish (Cyprinus carpio). Procedures: Twenty adult fish (sea bass, grey mullet catfish, and common carp), five of each species, were anaesthetized. Skin specimens were obtained from the dorsum side and fixed in 10% neutral-buffered formalin. The specimens were processed, treated using the normal histological technique, sectioned, stained with different stains, and examined using a light microscope. Results: The skin of the four species was comprised of the epidermis, dermis, and hypodermis. The epidermis consisted of three distinct layers. Two types of unicellular glands were present in the epidermis: club cells in the epidermis of catfish and common carp, and mucous cells in the epidermis of all fishes. Mucous cells reacted positively to AB/PAS staining. The club cells reacted positively to Bromophenol Blue staining. The dermis was formed by the stratum spongiosum and the stratum compactum. The latter was stained deeper than the spongy layer. The hypodermis consists of a layer of connective tissue containing adipocytes. Conclusion and clinical relevance: The present study concluded that the skin is adapted to the nature of the environment in which fish live. Keywords:Club cells, fish, mucous cell, skin.