An electron microscopic investigation of age-dependent changes in the flight muscle of Musca domestica L

The thoracic flight muscle from adult male NAIDM house flies was examined, from emergence to very old age. Thin sections stained with uranyl acetate and bismuth showed no myofibrillar or mitochondrial degeneration from 1 day to 19 days post-emergence, contrary to earlier reports. Some progressive loss in glycogen content and increase in mitochondrial size were observed for muscle from young to very old flies. However, there was no conclusive evidence of fusion of smaller mitochondria into larger ones with advancing age, despite exhaustive examination of representative sections of muscle samples of adult males of different ages.