VISUOMOTOR OPERATION IN TRANSITION FROM OBJECT FIXATION TO PREY SHOOTING IN CHAMELEONS

Video-records of the eye and head position of chameleons (two species) in relation to prey targets revealed the following: 1. Foveal fixatio n is performed monocularly for object identification before chameleons decide to catch the prey. 2. If the chameleon intends to catch the pr ey, it turns its head towards the prey in preparation for the tongue s hoot. While turning its head, the fixating eye does not continue to ke ep the target fixed foveally. Rather, it adopts a diverging position t o the head, the mediosagittal plane of which in the end is target-dire cted. 3. Ready for tongue shoot, the position of both eyes to the head is definitely adjusted at a fixed diverging angle of 17-19 deg, and t his position does not change at all with distance to the target. 4. Ch ameleons are also able to perform tongue shoots successfully using onl y one eye (the other being ocluded), and they use the same adjustment of prey to eye and eye to head as in the binocular case. 5. Thus, the correct direction of the tongue shoot in chameleons is processed by an extrafoveal retinotopic depiction of the prey image using monocular d istance information and a fixed eye in head position.