ULTRASTRUCTURE OF FISH CELLS INVOLVED IN CELLULAR DEFENSES AGAINST SAPROLEGNIA INFECTIONS - EVIDENCE OF NON-LEUKOCYTIC NATURE

Fish cells attached to hyphae were observed in brown trout Salmo trutt a L. infected with Saprolegnia parasitica. Earlier studies with light microscopy indicated that these cells were lymphocytes and neutrophils and that they were involved in the defence mechanisms against Saprole gnia infections. However, using electron microscopy, we found these at tached cells did not show leucocytic characteristics, but instead shar ed some ultrastructural features with filament-containing cells. The p resence of a dense mass of cytoplasmic filaments precludes the leucocy tic nature of these cells. How these cells could be involved in cellul ar defences against fungi is discussed.