Fig. 1.

Digital image of a Xenopus laevis tadpole (stage 52) in the flow tank, in no current conditions. Grid lines on the back wall of the tank are used as references to assist measurements of tilt angle. To determine tilt angle, two lines were drawn through the digitized image of the tadpole, using tools in KA video software. One line was the diagonal connecting the center of the eye point to the center of the gut point, both of which appear black. This line was made to intersect a horizontal line drawn through the center of gut point, parallel to the reference grid lines and extending in the direction at which the animal’s snout pointed. The angle between these two lines was automatically measured in the software program, and termed the tilt angle