Topography of vision and behaviour

In English Given the great range of visual systems, tasks and habitats, there is surprisingly little experimental evidence of how visual
limitations affect behavioural strategies under natural conditions. Analysing this relationship will require an experimental system
that allows for the synchronous measurement of visual cues and visually guided behaviour. The first step in quantifying visual
cues from an animal’s perspective is to understand the filter properties of its visual system. We examined the first stage of visual
processing – sampling by the ommatidial array – in the compound eye of the fiddler crab Uca vomeris. Using an in vivo
pseudopupil method we determined sizes and viewing directions of ommatidia and created a complete eye map of optical and
sampling resolution across the visual field. Our results reveal five distinct eye regions (ventral, dorsal, frontal, lateral and medial)
which exhibit clear differences in the organisation of the local sampling array, in particular with respect to the balance of
resolution and contrast sensitivity. We argue that, under global eye space constraints, these regional optimisations reflect the
information content and behavioural relevance of the corresponding parts of the visual field. In demonstrating the tight link
between visual sampling, visual cues and behavioural strategies, our analysis highlights how the study of natural behaviour and
natural stimuli is essential to our understanding and interpretation of the evolution and ecology of animal behaviour and the
design of sensory systems.