HISTOPATHOLOGY OF UV-B IRRADIATED BROWN TROUT SALMO-TRUTTA SKIN

Specimens of brown trout Salmo trutta L, were experimentally irradiate d with cumulative doses of UV-B (320-280 nm) ranging from 1368 to 6954 mJ cm(-2). After various postirradiation limes, skin samples of the d orsal region of the head were processed for microscopical observations . In the irradiated epidermis, 2 types of histological effects were ob served. Some effects were direct, immediate, and related to the loss o f cell layers, either by increased sloughing of the surface cells or b y massive detachment of the outer and middle layers. As a consequence, mucous cells disappeared from the irradiated epidermis. The restorati on of normal epidermis occurred by rapid processes of cell proliferati on and tissue closure resembling those of wound healing. Other effects of the W-B radiation were not immediate and involved the production o f so-called 'sunburn cells', characterized by fragmentation of the nuc lear material into dense granules. No qualitative differentiation into types A and B sunburn cells could be made. The interpretation of thes e sunburn cells as being apoptotic cells is discussed.