THEOBALD, JC; COATES, MM; Lund University, Sweden; Lund University, Sweden: Visual processing in the box jellyfish, Charybdea

Box jellyfish possess lenses and retinas capable of forming images, which is unique among cnidarians. This presumably allows them to exploit near-shore habitats too dangerous for other jellyfish. But the existence of these structures does not tell us what information they collect from the visual environment, or even prove they use spatial vision at all. Jellyfish lack a cephalized nervous system, and may use lenses as simple light gathering devices—the image formed on the retina would represent an unused artifact. We hypothesize that this is not the case, rather that box jellyfish process vision much like other visual animals: to extract spatial, temporal, and chromatic information. To test this, we performed behavioral experiments with Charybdea to determine their ability to perform two visual tasks which require downstream processing of photoreceptor input: color discrimination and motion detection. True color vision requires comparing relative responses from photoreceptors with different spectral sensitivities. Motion detection requires comparing responses from photoreceptors with different spatial regions at different times. Thus these are both second order senses. Charybdea succeed at both tasks; they exhibit wavelength specific behavior and possible color discrimination, and they respond to motion stimuli. These results imply box jellyfish collect and process visual information to produce appropriate behaviors.