ULTRASTRUCTURAL OBSERVATIONS ON PIGMENTED MACROPHAGES IN THE EPIDERMIS OF THE BROWN TROUT (SALMO-TRUTTA L)

Areas of disrupted tissue were found in the epidermis of the brown tro ut, Salmo trutta L., with inflammatory processes. In such regions, int rusive cells, mainly macrophages and neutrophils, appeared within a ba ckground of tissue remnants, forming a rericular meshwork between the detached malpighian cells. Both the disrupted epithelial tissue and th e migrating epidermal macrophages are ultrastructurally described. Sev eral types of pigment, including melanin, lipofuscin, plates of guanin e and others coming from engulfed dermal chromatophores, can be seen i n the macrophage lysosomal apparatus. Pigment formation by autophagic processes occurs in the neighbouring epithelial cells. In addition to the catabolic functions, others related to defence mechanisms are disc ussed with the aim of suggesting a similarity between epidermal macrop hages and those of other tissues, mainly the melano-macrophage centres .