Acidophilic granular cells in the epidermis of the brown trout, Salmo trutta L.

Acidophilic cells occur in the epidermis of several species of salmonid fish, although their abundance fluctuates considerable between individuals within the same population and at different times during the life cycle. The histology, histochemistry and ultrastructure of an acidophilic, granular cell-type in the epidermis of the brown trout, Salmo truuta L., is described. At the light microscope level this cell type is easily distinguished from the large, mucus-secreting, epidermal goblet cells by its acidophilic, proteinaceous secretion. At the ultrastructural level this secretion consists of membrane-bound granules formed by the very active Golgi region. It is argued that the acidophilic, granular cell is not a transformed blood cell but constitutes a normal epidermal component of the brown trout. Possible roles of this cell in the function(s) of the epidermis are discussed.