Meeting Abstract
To assess depth information, some animals utilize the disparity between left and right visual fields, in a process called stereopsis. This strategy is commonplace in vertebrates, having evolved multiple times independently. However, only one invertebrate species, the praying mantis, has been demonstrated to possess stereoscopic vision. Here, we set out to test for stereopsis in cuttlefish, a cephalopod mollusk. In addition to their notorious cognitive and camouflage abilities, cephalopods are visually driven hunters. The camera type eyes of cephalopods exhibit remarkable convergence to those of vertebrates, both in their anatomical features and vergence movements. However, neither squid or octopuses appear to employ stereopsis to resolve depth; squids use monocular retinal deformation and blur, and the limited overlap of visual fields from both eyes in octopuses makes the use of stereopsis unlikely. Cuttlefish, however, can produce significant binocular overlap through ocular vergence, though it remained unclear whether they employ stereopsis for their predatory attack. Here we show that cuttlefish (1) use stereovision to resolve the distance to prey, (2) use this information to shorten the time and distance covered prior to striking at a target, (3) likely process visual motion differently to vertebrates, as they can extract stereopsis cues from anti-correlated stimuli, and (4) can switch eye movements from independent to conjugated. These results show that stereopsis has evolved independently in another non-vertebrate group, but with camera-type eyes. Since the organization of the cephalopod brain is considerably dissimilar to that of vertebrates, this finding opens a door for investigating if cuttlefish have evolved alternate processing mechanisms for stereo perception.
