Ultrastructural changes in Nosema apis within the midgut of honeybees exposed to antiprotozoal drugs in vitro
T. P. Liu
Ultrastructural changes in sporonts of Nosema apis within the midgut of honeybees exposed to 3 antiprotozoal drugs have been examined by transmission electron microscopy. After exposure to fumagillin for 12 h, cytoplasmic density decreased in the sporont; otherwise, the ultrastructure appeared normal. After 24 h, the number of ribosomes decreased and ribosomal clusters tended to form. Drastic ultrastructural,changes occurred 12 h after the sporont had been exposed to emetine-HCl. The nucleoplasm became electron-lucent and the nuclear membrane lost definition. The endoplasmic reticulum either lost its membrane definition or became depleted of its ribosomes. Also, the cytoplasmic electron density decreased. Nuclear disintegration was observed in the sporont 24 h after treatment with emetine. Cytoplasmic condensation in the sporont 12 h after exposure to Formycin-B was observed. After 24 h of exposure, both the nucleoplasm and cytoplasm became electron-lucent, and the number of ribosomes appeared to decrease. These changes were confirmed by scanning electron microscope observations. These results suggest that all three drugs are potentially useful for controlling N. apis. The mechanism of action of each drug is discussed.