Figure 9.

Water transport velocity in the capillary system. Two typical examples of results of a frame-to-frame analysis of videos showing the transport of coloured water in the capillaries are shown for Phrynocephalus arabicus (A) and Phrynosoma cornutum (B). The velocities were measured in direction to the mouth (rostral, dark blue squares), towards the tail (caudal, light blue triangles) and sidewards (lateral, green diamonds). For Phrynocephalus arabicus (A) no significant difference can be seen when comparing the velocities in the different directions. The theoretical behaviour described by the Washburn-equation (solid black line) fits the data quite well suggesting simple capillary transport uniformly flowing in all directions. In contrast for Phrynosoma cornutum the typical result is that the velocity has a highly oscillating behaviour and, most interestingly, the velocity towards the mouth is normally higher than tailwards or sideways.