Mitochondrial heterosis in aging Drosophila hybrids.

Differences and temporal changes in mitochondrial activity were investigated in heterotic and nonheterotic Drosophila melanogasterF₁ reciprocal hybrids and respective inbred parents. Heterosis judged by heavier body weight, greater longevity and superior mitochondrial efficiency was exhibited by one reciprocal cross. In vitro mixtures of parental mitochondria complemented, that is, exhibited enhanced mitochondrial efficiency compared to the midparent average. Significant aging effects were reflected in changing mitochondrial ADP:O ratios, respiratory control ratios, and especially in state 3 respiration rates. Mitochondrial heterosis, judged by ADP:O ratios, was significant through 21 days of age and insignificant at later life stages, with some maternal influence noted. Non-heterotic hybrids exhibited negative mitochondrial heterosis at some growth stages.