Abstract
The current study aimed to explore the skin sructure at the larval and adult stages of the African catfish. Of the previous studies on the skin morphology of fish, none has researched the detailed skin differentiation at the larval and adult stages of the African catfish. Here by light microscopic investigation, the skin of the larva after hatching consisted of two layers of simple squamous epithelium. The skin of the 5-6 day old larva consisted of more than one layer of flattened to oval cells, continuous layer of melanocytes and club cells showed up. The skin of the 15-days old larva distinguished into epidermis, dermis and hypodermis. While the skin of the adult catfish, the epidermis consisted of three layers a basal layer of cuboidal or columnar cells, middle layer of polyhedral cells and surface layer of flattened cells. Its mucous cells were oval in shape having foamy cytoplasm. Its club cells had acidophilic cytoplasm and some cells were binucleated. At the lateral line, a group of elongated neuromasts viewed between the club cells. Langerhans like cell showed a positive reaction with CD 1a. The dermis divided into stratum spongiusm and stratum compactum. At lateral line beneath the hypodermis, the neuromast canal detected. By SEM, no any evidence of taste buds pores and neuromast detected at the newly hatched larva. Different forms of neuromast appeared on the surface as small epidermal protrusions at the 6-day old larva. In addition, the neuromast at the epidermal protrusion appeared with long and short hair bundles. While, the skin the adult catfish, the surface epithelium showed many projections, the broken epidermis showed a large club cells, melanocytes with cytoplasmic processes and pores. By TEM of the adult catfish, the surface cells had (microridges), desmosomes distinguished between the neighboring epidermal surface cells. The club cells cytoplasm had scanty organelles, two types of club cells identified; the first type with no vesicular secretion and the second type with fibrillar cytoplasm. The plasma membrane showed many invaginations. The study recorded two types of neuromast; superficial neuromast and canal neuromast set in the dermis. No neurmast detected at the 1st day larva afterthat it appeared and incresead in number and its shape changed from simillar hair cells to long and short hair bundles.

Key words: Catfish, Skin, Immunohistochemistry, SEM, TEM