Abstract
Cellular defense response of the silkworm, Bombyx mori, to the white muscardine fungus, Beauveria bassiana, was studied using phase-contrast microscopy, hemogram and histological sectioning. Adherence of viable conidia of B. bassiana to granular cells occurred within 10 min and the conidia were initially phagocytized by granular cells 5 hr postinjection, and the phagocytic rate reached the maximum after 12 hr. Plasmatocytes accompanied by granular cells might encapsulate conidia to form the melanized nodules 6 hr postinjection. The phagocytized or encapsulated conidia could germinate from phagocytized or nodules 24 hr postinjection. The total hemocyte count of the silkworm declined as a result of phagocytosis or nodule formation after injection of B. bassiana conidia. The present study indicates that the silkworm may exert temporarily a cellular response to the highly pathogenic fungal spores when injected with a high spore concentration.
