COATES, M.M.*; THOMPSON, S.H.: Vision in a cubozoan jellyfish.

Jellyfish of the class Cubozoa possess camera-type eyes similar to those of cephalopods and vertebrates; consisting of a lens, cornea, and retina. The retina is composed of three layers: a sensory layer, a pigmented layer, and a nuclear layer with extending nerve fibers. The cells of the retina are all ciliated primary photoreceptors. These complex eyes are located on sensory clubs called rhopalia. Each animal has four rhopalia, and each rhopalium has two camera-type eyes as well as four simple ocelli. In spite of all this visual hardware, little is known of the visual capabilities of these animals and specifically the function of the remarkable complex eyes. We want to determine what information these eyes extract from the environment and how the nervous system processes that information. We are studying these questions using behavioral and electrophysiological approaches. At Hopkins Marine Station, we have established a colony of Tripedalia cystophora, a small cubozoan from Puerto Rico. These cubomedusae exhibit strong attraction to light. Taking advantage of this behavior, we measured the spectral sensitivity curve of the eye and performed wavelength discrimination experiments. We then used extracellular recording methods to measure the electroretinogram (ERG) of the complex eye in response to flashes of different wavelengths and durations. This allowed us to compare the spectral sensitivity of behavioral responses to the retinal spectral sensitivity and to learn response time characteristics. This will help elucidate the type and quality of visual information available to this cubozoan. Funding: NSF and Myers Grant to M.C.; NSF to S.T.