It may seem like a childish prank, but a team of researchers from the University of Minnesota (USA) has carried out a curious experiment that consisted of putting 3D glasses on a cuttlefish and putting it in a kind of underwater theater in which they projected images of appetizing prawns. The goal: to study the vision of these intelligent cephalopods and find out how they manage to determine the distance to their prey.
The results, published in the journal Science Advances , revealed that cuttlefish use steropsis to achieve total precision in their hunting movements. This phenomenon of visual perception is what allows, from the two slightly different images that come from each eye, to recompose the three-dimensional photo of what is perceived. Thanks to stereopsis, for example, humans are able to see in depth.
This was the experiment
Imagine that you are a cuttlefish and you have to hunt a prey. To be successful the first time and not scare it away, you must be able to position yourself at the exact distance: if you are very far, your tentacles will not be able to reach it, but if you get too close, it can detect you earlier than expected and flee.
To determine how these invertebrates calculate the distance to their prey, the scientists conducted their experiment in a pond with a screen on which 3D images of a prawn were projected. When the cuttlefish were put on the 3D glasses, the cuttlefish thought the shrimp was in the middle of the pond and was much further away from the screen than when it was not wearing glasses. This reveals that, as we have mentioned, cuttlefish use stereopsis to see and hunt, and are capable of integrating the images that come from both eyes to see in depth. Although traditionally it was thought that this phenomenon was something unique to vertebrates, studies like this reveal that some invertebrates also have this ability, although the process is not exactly the same as that which occurs in humans.
“While cuttlefish have human-like eyes, their brains are significantly different,” explained Paloma González-Bellido, assistant professor in the Department of Ecology, Evolution and Behavior at the School of Biological Sciences at the University of Minnesota. ” We know that the brains of cuttlefish are not segmented like those of humans. That is, in principle they would not have a specific part of the brain, such as our occipital lobe, dedicated to processing vision. Our research shows that there must be an area in his brain to compare the images of the left and right eye of a cuttlefish and calculate the differences, “he concludes.
The eyes of the cuttlefish are highly developed, much more so than those of squid and octopus, and the researchers argue that these animals are perhaps the only cephalopods with the ability to use stereopsis to calculate distances. Although the development of the nervous system of cuttlefish is different from that of vertebrates, the truth is that the final function is very similar. “This study takes us a step further to understand how different nervous systems have evolved to address the same problem,” explained Rachael Feord, first author of the research paper. “The next step will be to dissect the brain circuits necessary for the calculation of stereopsis in cuttlefish to evaluate the differences in functioning with the human brain.”
