Substrates of oxidative metabolism in Dipteran flight muscle.

A comparison was made of the capacity of mitochondria from the flight muscle of several species of Diptera to oxidise pyruvate, alpha -glycerophosphate and proline. The species studied fall into three main groups distinguished on the basis of their ability to oxidise pyruvate or proline, or both, at rates commensurate with the requirements of flight metabolism. One group comprises species which do not feed on blood (Musca domestica L. and Sarcophaga nodosa Engel), or of which only the female is bloodsucking (species of Tabanus, Haematopota and Philoliche), and in this group only pyruvate is oxidised at the requisite rate. A second group includes species of which both sexes are facultative bloodsuckers (Haematobia sp. and Stomoxys calcitrans (L.) and this group both substrates support high rates of oxidisation. The third group is constituted by two species of Glossina, in which both sexes are obligatory bloodsuckers, and in these proline constitutes the only effective substrate for flight metabolism. The results are consistent with the view that the capacity to oxidise proline by different species of Diptera may be seen as a metabolic adaptation to the bloodsucking mode of life.