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Histopathology of UV-B irradiated brown trout Salmo trutta skin

Abstract:

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