Effect of reduced O2 levels on D. melanogaster
metabolic rate (measured as CO2 production). The metabolic response
to hypoxia data are from metabolic rates determined at 28 different
O2 tensions measured in six independent groups of flies. Data are
means ± s.e.m. (A) metabolic rates at O2 tensions ranging
from normoxia to 0 kPa. The asterisk indicates when metabolic rate is first
significantly reduced compared with normoxia, and the open symbols are the
metabolic rate of control groups not exposed to hypoxia. (B) The lower range
of the same data plotted at higher resolution. The two lines are the average
change in metabolic rate for O2 tensions between 0.1 and 0.6 kPa,
and 0.7 and 3.1 kPa. The equation describing the relationship between relative
metabolic rate and O2 tension in extreme hypoxia is:
MR=0.75x+0.04, r2=0.94; and for less extreme
hypoxia MR=0.16x+0.4, r2=0.83, with x as
the PO2. (C) Recovery of fly metabolic rate
after exposure to anoxia. (D) The RQ (respiratory quotient) and relative
metabolic rate of flies progressively exposed to O2 tensions of
1.2, 0.8, 0.4, 0.2 kPa. Open symbols are the relative metabolic rate and RQ of
flies maintained in normoxic conditions. Data are from five groups of flies
exposed to hypoxia and three control groups.