It has been suggested that long-lived species and long-lived artificially selected strains consume more oxygen than short-lived organisms. With a simple and highly repeatable technique we observe the opposite trend early in life. Specifically, the long-lived HW09 flies consume lowest levels of oxygen at day 11. These data suggest that less oxygen is needed early in the life of HW09 flies and provides the first line of evidence to suggest this line has an increased efficiency of oxidative metabolism.

The rate of oxygen consumption by whole flies was measured using microrespirometers. These were constructed by first attaching a 25 ul/76 mm (0.3µl/mm) microcapillary pipette over a 25-gauge hypodermic needle with silicone sealant. The microcapillary pipette-needle assembly was then attached to a 1 cm3 tuberculin syringe and a small cotton plug was inserted into the needle end of the syringe chamber. Male flies of the same line and age were anesthetized on ice and ten flies were placed into the barrel of the syringe. A second cotton plug was then inserted into the syringe chamber and positioned to restrict the ability of the flies to move. A 1 cm filter paper, soaked in a saturated solution of KOH, was placed in the barrel of the syringe to absorb carbon dioxide and the syringe plunger was inserted to seal the chamber. To measure oxygen consumption the microrespirometers were allowed to equilibrate for 30 minutes at 24C. A small drop of dye was then placed into the end of the capillary pipette and the position of the drop’s leading edge was marked. After 10 minutes at 24C the position of the leading edge of the dye drop was marked again and the distance moved in millimeters was recorded. The movement of the dye drop down the capillary pipette gives a measure of oxygen consumption in µl/mm over time. Flies were anesthetized on ice while still in the microrespirometers,and the milligram weight of all ten flies together was determined. The volume of oxygen consumed per minute was calculated by subtracting the mean movement of the dye drop in the control microrespirometers from that in each of the experimentals. Because the molar quantity of a volume of oxygen varies with temperature and pressure we adjusted the measured volumes to standard conditions [1].

VolSTD = VolMEAS x [273 K/ Ambient K] x [Ambient Pressure (mm Hg)/ 760mm Hg] .......................................................... [1]