Zoom Colloquium: Extreme nature - Ocular motor control in Chameleons

Chameleons are considered a potentially important model for vision in non-mammalian vertebrates. They provide exceptional behavioral tools for studying eye movements as well as information gathering and analysis. They perform large-amplitude eye movements that are frequently referred to as independent, or disconjugate. Moreover, they have fully decussated optic nerves with intertectal connections that are not as developed as in mammals. Optical adaptations for arboreal life and insectivoury result in retinal image enlargement and the unique capacity to determine target distance by accommodation cues. However, the extent of the eyes’ independence is unclear. For example, can a chameleon visually track two targets simultaneously and monocularly, i.e. one with each eye? And what will be the ocular motor control pattern of the eyes?

With their extreme visual capacities, chameleons open the field of lateralization, decision making, and context dependence visual behavior. They allow a deeper examination of the relationships between their unique visuo-motor capacities and the central nervous system of reptiles and ectotherms, in general, as compared with mammals.