COATES, M.C.; THEOBALD, J.C.; Stanford University; University of Washington: Optimal visual parameters for a cubozoan jellyfish in the mangrove environment

The cubomedusans are unique among Cnidarians in possessing eyes capable of forming images, but how these eyes are used in the wild is a mystery. Our hypothesis is that detecting self motion is a major purpose, and this allows cubomedusans to exploit nearshore environments. To investigate this question, we produced a model of visual processing using measured optical and physiological parameters. Into this we input images from mangroves where we observed the small jellyfish Tripedalia cystophora. We found that the actual parameters of vision closely matched those optimal for detecting self motion. The mangrove is a rich visual environment. Acuity too low transmits little of this information. Acuity too high, however, transmits information that can be considered noise in the context of detecting self motion. We have observed other eyeless jellyfish that fatally collide and entangle with the objects in the mangrove, while Tripedalia navigate flawlessly. These results support the hypothesis that vision adapted cubomedusans from pelagic environments to the safe and resource rich mangrove environment.