Table 2.

Blood oxygen affinity in vitro at two PCO2 levels (2% and 5% CO2) in fasting and digesting snakes (Python molurus)

ExperimentBefore feeding (0h)After feeding (48h)Control (0h)Control (48h)
CO2 level2% CO25% CO22% CO25% CO22% CO25% CO22% CO25% CO2
pH7.57±0.02 (9)7.31±0.02 (9)7.65±0.03 (9)*7.40±0.02 (7),*7.63±0.02 (5)7.34±0.02 (5)7.66±0.03 (4)*7.37±0.02 (4)
P50 (kPa)4.67±0.07 (9)5.36±0.10 (9)3.42±0.19 (9)*4.43±0.31 (7),*4.39±0.12 (5)5.38±0.19 (5)4.40±0.19 (4)5.38±0.23 (4)
logP500.67±0.01 (9)0.73±0.01 (9)0.53±0.02 (9)*0.64±0.04 (7),*0.64±0.01 (5)0.73±0.01 (5)0.64±0.02 (4)0.73±0.02 (4)
n 2.86±0.16 (9)2.64±0.14 (9)2.42±0.17 (9)*2.36±0.15 (7)2.88±0.10 (5)2.47±0.13 (5)2.47±0.20 (4)2.50±0.02 (4)
Bohr effect (Φ)-0.23±0.02 (9)-0.36±0.03 (7)*-0.31±0.02 (5)-0.30±0.01 (4)
  • Data for snakes that were not fed but sampled at a 48 h interval are also included (unfed control).

    pH, pH measured in the tonometers; P50, oxygen tension at half saturation; n, Hills coefficient for cooperativity of oxygen binding; Bohr effect (Φ), calculated as▵ logP50/▵pH. Values are means ± S.E.M. (N).

  • * signifies statistical difference between values at 0 h and 48 h; signifies statistical difference between values at 2% and 5% CO2 within each experimental condition.