Effects of temperature on Drosophila—VI. Respiratory enzymes

• 1.

  1. The activities of malic dehydrogenase, malic oxidase, succinic dehydrogenase, succinic oxidase and cytochrome oxidase were measured in homogenates of whole adult male and female Drosophila melanogaster grown at 15 and at 25°C. The activities assayed at 15 and 25°C are reported and only with succinic dehydrogenase was evidence of temperature adaptation noted.

• 2.

  2. The activities of malic oxidase, malic dehydrogenase, succinic dehydrogenase and cytochrome oxidase were assayed in D. pseudoobscura grown at 15 and at 25°C. There was no evidence of temperature adaptation in the activities measured at 15 and at 25°C.

• 3.

  3. Malic dehydrogenase and cytochrome oxidase were assayed in D. willistoni grown at 15 and at 25°C. The flies grown at the lower temperature have higher enzyme activity than those grown at 25°C. This is interpreted as a capacity adaptation.

• 4.

  4. It is suggested that temperature adaptation would not be expected with some of these enzymes because their Q₁₀ values are low. In general, the results reported here do not add support to the theory that eurythermal species such as D. melanogaster have a greater capacity for temperature adaptation than do stenothermal species such as D. pseudoobscura and D. willistoni.