[Ecdysone-dependent changes in the activity of ontogenetic puffs in the salivary glands of Drosophila cultivated in vitro as regards the effect of heterosis and selection of adaptively significant characters].

Regression of 4 intermolt and induction of 14 early ecdysone puffs in two inbred stocks of Drosophila with high (HA) and low (LA) activity and hybrid F1 HA x LA were studied. Experiments were performed in vitro with ecdysone-containing media. Differences in developmental rate and fitness of stocks HA, LA and their hybrid were shown to correlate with the rate of change in polythene chromosomes puffing activity. Adaptive heterosis and ontogenetic homeostasis mechanisms are under discussion in connection with the results obtained.