Meeting Abstract
Research on visual systems has focused primarily on the paired cephalic eyes found in many taxa, but these are not the only eyes in the natural world. It is likely that we have much to learn from distributed visual systems that include dozens or hundreds of separate light-detecting structures. To better understand relationships between the structure and function of distributed visual systems, we are comparing how morphological differences between light-sensing structures in chitons relate to the visually-guided behaviors of these animals. Sensory organs – termed aesthetes – are embedded within the shell plates of all chitons. In some species, the aesthetes are interspersed with small eyes. In other species, each aesthete is associated with an eyespot. Previously, we established that the eyes of chitons are associated with spatial vision. Here, we find that chitons with eyespots also engage in behaviors consistent with spatial vision. For example, we find that Chiton tuberculatus orients to static objects with angular sizes as small as 10°. We also note morphological differences between species of Chiton that may be relevant to vision: the eyespots in some species (e.g. C. tuberculatus) lie underneath shell material that is transparent and convex, whereas eyespots in other species (e.g. C. marmoratus) are associated with overlying shell material that is transparent, but flat. We also find that the eyespots of Chiton are separated by narrow angles (0.5°) similar to those observed between the ommatidia of high-acuity apposition compound eyes. Lastly, we explore the degree to which chitons may gather spatial information by comparing input between photoreceptors within neighboring light-detecting structures rather than comparing input between photoreceptors within the same structures.
