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Odd pupils could be key to camouflage trick of colorblind octopi and squid

by • July 5, 2016 • No Comments

Despite their talent to alter color to perfectly match their surroundings, cephalopods like octopi and cuttlefish are in fact colorblind, having only one photoreceptor, unlike the three we humans possess. The way in which they can pull off their camouflage trick and so, has been a source of speculation for scientists for a few time. Now, father and son scientists of two universities believes they’ve cracked the mystery – and it all has to do with a few strange pupils.

In the human vision process – and which of many other mammals as well – the eyes have relatively tiny pupils which focus light to a exact point on the cones contained in our retinas at the back of our eyes. This creates a sharp image.

But, if you’ve at any time gone to the eye doctor and had your pupil dilated, you’ve no doubt noticed which things appear a little fuzzier and light sources tend to have a kind of colorful halo around them. That effect is called chromatic aberration and it turns out cephalopods see the world which way fairly much all the time.

Their pupils tend to have the wide-open shape of a U, W or actually a dumbbell in the case of a few species of octopi. Such a pupil create does not focus the light, but pretty, lets it come in of all angles, creating a blurry image. But, according to new research out of the University of California Berkeley (UC Berkeley) and Harvard University, cephalopods can alter the depth of their eyeball and move their oddly-shaped pupils around to bring specific wavelengths – i.e. colors – into focus on their retinas.

The oddly shaped pupils of a cuttlefish, squid and octopus of top to bottom

So actually yet they don’t have the photoreceptor talent to see colors we do, their eyes have modified
to sense color in a completely various way. They may not have clear vision, but they have vision which lets them sense and blend into their surroundings, which may only be a extra
valuable evolutionary version than sharp sight.

“We propose which these creatures can exploit a ubiquitous source of image degradation in animal eyes, turning a bug into a feature,” said UC Berkeley graduate student Alexander Stubbs. “While many organisms evolve ways to decrease this effect, the U-shaped pupils of octopus and their squid and cuttlefish relatives in fact maximize this imperfection in their visual process while minimizing other sources of image error, blurring their view of the world but in a color-dependent way and opening the possibility for them to get color information.”

Stubbs, who’s long had an interested in the colorblind/camouflage conundrum of cephalopods worked with his father, Harvard astrophysicist Christopher Stubbs, to create a desktop simulation version which played with various ways in which cephalopod eyes can work. Their findings were published in the journal Proceedings of the National Academy of Sciences online this week.

“We believe we have discovered an elegant mechanism which may allow these cephalopods to determine the color of their surroundings, despite having a single visual pigment in their retina,” Stubbs said. “This is an entirely various scheme than the multi-color visual pigments which are common in humans and many other animals. We hope this study can spur extra
behavioral experiments by the cephalopod community.”

The UC Berkeley video at a lower place shows off the awe-inspiring color-changing abilities of cephalopods, with a great close-up of one of the creature’s eyes.

Source: Berkeley News


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