The Effect of Carbon Monoxide on the Oxygen Consumption of Drosophila Melanogaster Pupae

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Abstract
1.The oxygen consumption of Drosophila melanogaster pupae during metamorphosis can be expressed by a U-shaped curve, as stated by earlier authors; that is, the consumption is high at the beginning, then falls off rapidly, and from the middle of the pupal period onwards it rises again till about the original level. 2. The oxygen consumption is strongly inhibited by carbon monoxide in all pupal stages. The inhibition is proportional to the percentage of CO and O2 in the gas mixtures and can be expressed by the formula of Warburg (1927) n/1-n·CO/O2=K The validity of this formula means that in Drosophila pupae the oxidizing enzyme system (Warburg-Keilin system) is saturated during the whole period of metamorphosis. 3. The CO effect decreases markedly at the time when the oxygen uptake begins to rise again (the "turning point" of the respiratory curve). Accordingly the value of K increases at this stage. The bearing of this is discussed. 4. The CO effect on oxygen consumption is sensitive to light and can be counteracted to a certain extent by illumination (the limiting factor being probably the opacity of tissues).