Society for Neuroscience Conference Poster

Post date: Dec 02, 2019 10:57:55 PM

There is a growing realization that low-resolution eyes can be used for complex visual tasks. It was previously thought that the simple eyes of nudibranch molluscs, comprised of a spherical lens, pigment cells, and about five photoreceptor cells, were not capable of providing spatial information about the environment. We examined the ultrastructure of the eye in the nudibranch, Berghia stephanieae. Thin sections were acquired using automated tape-collecting ultramicrotome and electron microscopy (EM). We identified a previously unreported conical structure in the back of the eye, possibly of rhabdomeric origin, that may function in photoreception. We are further examining the connectivity of photoreceptor cells in the eye using both light level and serial EM reconstruction. Despite the simplicity of the eye, we found behavioral evidence of spatial vision in Berghia; when placed in the center of a circular tank surrounded by a white wall interrupted with a single black stripe, Berghia reliably navigated toward this stripe and crawled up the wall of the tank. The presence of a visual target elicited directed locomotion; in the absence of a visual target, locomotor paths were undirected, longer, and more convoluted. Berghia responded to stripes as thin as 15degrees of visual angle, but seemed to prefer 45degrees. We hypothesized that Berghia were attracted to the stripe because they seek shelter under objects. Berghia did not crawl towards visual targets that lacked features of an accessible shelter, such as a white stripe or a black stripe that did not reach the floor of the arena. Navigation toward black stripes was reduced in hungry animals, a motivational state that typically increases exploratory behaviors such as foraging. These results suggest the simple eyes of Berghia provide it with spatial information that they use to navigate toward targets that appear to be shelters. We aim to determine the neural mechanisms that allow a structurally simple eye to guide spatial vision used for motivated behaviors.