Cuttlefish are among the most remarkable of cephalopods, but nobody expected the creatures to have this particular trick up their sleeve. Cuttlefish can actually see information in the angle of intense polarized light that we can barely comprehend.
We're generally most familiar with this particular concept from polarized sunglasses. The idea is that light that was otherwise scattered in all directions is reflected off a surface so that the light is oriented in one direction, creating a massive, intense glare. Polarized sunglasses are used to counter this effect and block out most of the reflected light. And, as far as we humans are concerned, that's pretty much the end of it. Polarized light creates glare when we're dealing with large, flat surfaces - anything from a body of water to a long stretch of highway - and we can use special sunglasses to block out the worst of this intense light.
But cuttlefish, those marvelous mollusks, can do something far more remarkable. They can actually see the angle at which the light is reflected and polarized, and even the subtlest change will activate their color-changing defense mechanism, as researchers at the University of Bristol and University of Queensland recently discovered. Bristol lead researcher Dr. Shelby Temple explains how they made the discovery:
"We modified LCD computer monitors to show changes in polarization instead of changes in colour, and then played videos of approaching objects and watched for changes in skin colour patterns to determine if the cuttlefish could see small changes in polarization contrast. Cuttlefish change colour all the time and respond to the slightest movement so they are an excellent model. Cuttlefish were much more sensitive than we expected. It was previously thought that polarization sensitivity was limited to about 10-20 degree differences, but we found that cuttlefish could respond to differences as small as one degree."
We knew that cuttlefish, along with their cephalopod cousins the octopus and squid, could see polarized light in this way, but we had no idea they could see this well. Of course, when you've got an eye as weird as the one up top, maybe it isn't so hard to believe that they see the world like no other species. Because the idea of seeing the angle of polarization is so alien to us, the researchers are still grappling with all the hidden visual information cuttlefish are able to see. To that end, they are replacing the polarization angles in underwater scenes with different colors to get a better sense of just what is really in the cuttlefish field of vision. Brisbane researcher Justin Marshall adds:
"These extraordinary findings suggest that we need to reexamine how we have been measuring the visual world underwater. Cuttlefish may be using the polarization of light much like we use colour, which means we may need to look at camouflage and communication underwater in a whole new way."
Via Current Biology. Image by FireFly5 on Wikimedia.