Fig. 7. The phase shift between the mantle and the anterior vena cava (AVC) plotted against the ventilation rate: heart rate ratio. Fig. 6 shows the variation in the phase shift between mantle and AVC contractions between animals. This variation is largely explained by how many times the mantle contracts per heart contraction (linear regression: r²=0.98, P=0.0082, N=4). Each symbol represents averaged data from one cuttlefish.