Abstract
The homogenates from the larval tissues of the silkworm, Bombyx mori infected with Nosema sp. M11 or Pleistophora sp. were infective to Antheraea eucalypti cells in vitro. The homogenates placed in Grace's insect medium maintained their infectivity to the A. eucalypti cells for at least 12 hours. When the homogenates were added to the culture, infection of these two Microsporideae and the rates of infection increased with time up to three hours. When observed under an electron microscope, the infectious bodies of the Microsporideae in culture cells showed the same structural features as those of their sporoplasms. Among the fractions obtained through isotonic Percoll density equilibrium centrifugation, only sporoblast and spore fractions of Nosema sp. M11, and spore fraction of Pleistophora sp. were able to infect A. eucalypti. The very few spores of Nosema sp. M11 fractionated by Percoll centrifugation, and the spores contained in the homogenate were found to extrude their polar filaments and sporoplasms in the Grace's medium at 26°C within a day. These results indicate that the infectivity of homogenates to A. eucalypti cells in vitro resulted from autogermination of spores in Grace's medium.
