Cytological changes in the fat body of Rhodnius during starvation, feeding and oxygen want.

Fourth-stage larvae of Rhodnius survive starvation for 7-9 months. The filamentous mitochondria in the fat-body cells become reduced to granules and short rods (say 16 weeks). By 25 weeks the granules are swollen to form spheres which still contain NAD-diaphorase. By 30-35 weeks many mitochondria break down to osmiophil spheres or cytolysomes containing acid phosphatase. The origin of these spheres agrees with that of' protein droplets' in holometabolous insects. After feeding, the nucleus and nucleolus enlarge, RNA begins to accumulate in the cytoplasm and both the granular and the enlarged spherical mitochondria develop into filaments which break up into rows of granules. Within 2 days the fat-body cells become distended with watery vacuoles. All these changes are arrested or delayed if the oxygen supply to the fat body is reduced by tracheal section. Mitosis is hardly affected. Accumulation of reserves of fat and glycogen takes place later.