Ultrastructural differences of neurosecretion granules in the corpora cardiaca of the honeybee with and without infection by Nosema apis.
Axons of corpora cardiaca in the Nosema infected honeybees contained numerous tightly packed neurosecretion granules. These granules invariably possessed high electron densities. Neurosecretion granules of similar size were also observed in the axons of corpora cardiaca in the healthy honeybees. But these granules were shown to possess various electron densities. Image analysis revealed that some of these granules possessed an electron dense core, and the electron densities decreased gradually from the core, to the fringe of the granule. Some granules appeared to be completely broken down into fine granular substances, while others appeared to be completely broken down into finer particles. It is suggested that in the healthy honeybees, the releasing of neurosecretion from the corpora cardiaca had taken place normally, whereas in the diseased bee, the releasing mechanism had been blocked. The blockage is probably due to the infection.
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Bee Diseases Research Laboratory, Agriculture Canada Research Station, Box 29, Beaverlodge, Alberta, Canada T0H 0C0.