Oxygen uptake (V˙O2—mLO2 kg1 h1) was measured
by flow-through respirometry adjusted according to the
method of Steffensen (1989) to ascertain steady state
condition in less than 1 h. The oxygen tensions of the
ingoing (PinO2) and outgoing (PoutO2) water were continuously
measured. This was achieved by siphoning water
samples via polyethylene catheters to O2 electrodes (FAC
001-O2, FAC—Sa˜o Carlos, SP, Brazil) that were housed
within a temperature controlled cuvette and connected to a
FAC-204A O2 Analyzer. Oxygen uptake was calculated as:
˙V
VO2 ¼ VRIaðPinO2 PoutO2Þ=Wt;