Fig. 2. Anatomical landmarks digitized (black points) with the calculated kinematic variables (arrows) on the lateral (A) and ventral (B) high-speed video images of Clarias gariepinus. The landmarks are: 1, middle of the eye; 2, upper jaw tip, interior side; 3, lower jaw tip, interior side; 4, tip of the hyoid; 5, most ventrally positioned point of the branchiostegal membrane; 6, rostral tip of the skull roof; 7, caudal tip of the skull roof; 8, anterior tip of the caudal fin; 9, hyoid symphysis; 10,11, most caudally discernible points on the hyoid bars; 12,14, base of pectoral spine; 13,15, lateral tip of the branchiostegal membrane. The measured linear variables are: gape distance (a), hyoid depression (b), branchiostegal depression (c) and lateral branchiostegal expansion (f, average between left and right). The angular variables are: neurocranial elevation (d) and lateral hyoid abduction (e). The red lines represent the coordinate system moving with the head of the catfish.