Behind the eyes of a leech. How simple eyes encode complex image features that inform behavior

Dept. of Biology Seminar

Presented by Dr. John Jellies, Department of Biological Sciences, Western Michigan University

Abstract: Using light to extract information about environments is widespread and beneficial for survival. Almost all animals have evolved specialized sensory capabilities to detect light and inform adaptive behaviors. Indeed, it has been estimated that eyes have evolved independently across Phyla upwards of 60 times, yet many of the substrates to generate eyes and the genes to guide their development have been highly conserved. Visual systems also show a remarkable diversity of feature extracting capabilities from simple level detection to time-dependent spatial frequency comparisons across spectra. Ciliary photoreceptors, rhodopsin and, complex image-forming camera type eyes are found in Cnidaria, and are thought to predate the evolution of bilateral animals. We are interested in understanding broadly how nervous systems detect visual cues and encode features of image that can then be used to drive adaptive behavior in species-specific ways. Our work with carnivorous leeches has revealed that even without image-forming eyes, they use multiple simple eyes in discrete somatotopic arrays to sample the visual field and convey complex information into the CNS about the dynamic visual space of the worm. Leeches possess a multiplex system with cephalic eyes as well as dermal eyes. Different eyes are tuned to preferentially encode information about visible and ultraviolet light as well as temporal features of contrast. I will provide a brief overview of feature extraction, image formation and some of the challenges that are faced by visual systems across phyla and then provide a summary of several of ways we have discovered that leech eye encode spatial, spectral and luminal cues to drive behavior.