Meeting Abstract
Most research on visual systems has focused on animals with paired cephalic eyes; however, some animals have distributed visual systems in which many eyes are distributed across their body. Compared to animals with paired cephalic eyes, these animals have nervous systems that are less centralized and less cephalized, which seems at odds with their multitude of eyes and the common notion that vision is an information-rich modality. In most cases it is unknown how these animals process the large amount of information being gathered by their visual systems. To compare neural processing in animals with different distributed visual systems, we studied the bay scallop A. irradians and the chiton A. granulata. A. irradians has dozens of mirror-based eyes, and A. granulata has hundreds of eyes embedded in its dorsal shell plates. In both species, we injected fluorescent dyes into eyes to trace the optic nerves to their site of innervation. We found that optic nerves from the eyes of A. irradians lead centrally to the parietovisceral ganglion, suggesting central processing of visual information in scallops. In contrast, we found the optic nerves of A. granulata lead locally to the lateral nerve cord, suggesting distributed processing of visual information in chitons. Thus, we find two species with distributed visual systems use different strategies for neural processing, with scallops employing centralized processing and chitons employing distributed processing. These different processing strategies may represent underlying differences between nervous systems in which processing occur in ganglia (e.g. scallops and other bivalves) and those in which processing occurs in medullary cords (e.g. chitons and other molluscs).
