Factors influencing the structure, function and biota of the salmonid epidermis

Abstract

SynopsisThe present contribution shows the extent and the limitations of our knowledge of the structure, functions and biota of the epidermis of just one family of teleost fish, the Salmonidae. Even within this group it is clear that the epidermis can respond, with remarkable rapidity in some cases, to changes in the environment and to internal stimuli, presumably mediated via the fish's endocrine system. Against this background of constantly changing structure it is believed that the emphasis of the multiple functions of the epidermis must also be changing. Thus, future studies on the skin offish must take into account the possibility of such variations and relate the biology of the skin and its inhabitants to broader aspects of the biology of the fish.

Functions for fish mucus

“…Prolactin levels in vivo are influenced by a range of environmental variables including calcium concentrations and osmolarity (Wendelaar Bonga and Meis, 1981). Other hormones are known to influence the production or release of mucus: oestrogens and androgens (Picketing and Richards, 1980); testosterones (De Ruiter and Mein, 1982;Burton and Everard, 1991); cortisol (Marshall, 1979). It is, however, the undoubted role of prolactin as the regulatory factor that controls sodium efflux from the fish surface (Evans, 1984) that has led to the suggestion that perhaps prolactin restricts sodium efflux by stimulating the production or release of mucus.…”

Role of viruses in the induction of skin tumours and tumourlike proliferations of fish

“…Antibodies, specific agglutinins and molecules with possible antibiotic activity are almost exclusively found in skin mucus (Pickering & Richards 1980) whereas macrophages and lymphocytes are frequent inhabitants of the epidermis (Bullock & Roberts 1974, Roberts & Bullock 1980.…”

Effect of rearing temperature on larval growth and the development in different tilapia species

“…A number of functions have been ascribed to the mucous layer, such as friction reduction (Pickering, 1974), protection against injury (Pickering and Richards, 1980), and ionoregulation. The mucus coat of fish also forms the primary barrier against infection (Pickering, 1974;Pickering and Macey, 1977;Ingram, 1980), and fish skin mucus may inhibit the growth of bacteria (Harrell et al, 1976;Fouz et al, 1990).…”