Meeting Abstract

S11-2  Sunday, Jan. 8 08:30 - 09:00  Function and evolution of the dispersed visual systems of bivalves and chitons SPEISER, D.I.; University of South Carolina speiser@mailbox.sc.edu http://speiserlab.com

Compared to eyes that provide high spatial resolution (such as the paired cephalic eyes of many vertebrates, cephalopods, and arthropods), eyes that provide low spatial resolution have received relatively small amounts of attention from researchers. Here, using a diverse set of molluscan models, I will argue that low-resolution visual systems have much to teach us about the function and evolution of eyes. First, low-resolution eyes tend to be less complex overall than high-resolution eyes, but their apparent simplicity can mask unique or sophisticated features. The eyes of scallops, for example, form images using unique, mirror-based optics and sample these images with two separate retinas. In addition to these uncommon structural features, we are accumulating evidence that the eyes of scallops are dynamic structures that change shape in response to different environmental conditions. Second, we find that many animals with low spatial resolution vision have a multitude of eyes, but we know very little about the neural processing that underlies these dispersed visual systems. In the case of scallops, how do animals process the images gathered separately by their dozens to hundreds of eyes? Do they integrate information from multiple eyes so that a single reconstruction of their visual environment is formed? Third, a phylogenetic perspective on the distribution of light-detecting structures across taxa suggests that low-resolution visual systems may have evolved relatively recently in certain groups. These groups represent promising opportunities for using comparative molecular techniques to study how eyes may evolve from non-eye structures. To illustrate this point, I will discuss how we are using the distribution of different light-detecting structures across chitons (Mollusca: Polyplacophora) to reconstruct a step-by-step account of how and why eyes evolved in certain taxa within this group.