Joel Kontinen
Squid are fascinating creatures. They use jet propulsion to dart through the water and can even fly above the surface over a short distance.
They can hide from predators by changing colour.
These are not the only design features in this animal that can rightfully be called a living fossil. Even its ink has not changed in “150 million years”.
Recently, Science published a paper on how squid can see clearly in water:
“It’s hard to see underwater, and not just because of the chlorine. The image-producing light rays that enter our eyes have trouble bending and focusing when the water’s density is almost same as that of eye fluid. Sea creatures experience the same problem, but squid use a type of lens notorious for blurry images to correct that, researchers report today in Science. Spherical lenses, like the squids’, usually can’t focus the incoming light to one point as it passes through the curved surface, which causes an unclear image. The only way to correct this is by bending each ray of light differently as it falls on each location of the lens’s surface.”
So far, so good. But then they attribute a cleverly designed feature to blind evolution:
“S-crystallin, the main protein in squid lenses, evolved the ability to do this by behaving as patchy colloids—small molecules that have spots of molecular glue that they use to stick together in clusters. The S-crystallins feature a pair of loops that act as the proteins’ sticky patches and attract the loops of other S-crystallins. Globs of six proteins link together during the squid’s larval stage and form a gel that eventually becomes the center of the lens. As the gel becomes too dense with protein clumps, smaller particles struggle to diffuse through, and a new layer of protein packages forms with just under six S-crystallins in each clump. The process continues until the outer edge of the lens is formed with pairs of S-crystallins. This allows light rays to bend a little differently in each region of the lens, which yields a clearer image.”
Invoking evolution is totally unnecessary. A protein does not have the ability to evolve anything.
It is clear that like the intricate trilobite eye, squids also defy Darwinian just so stories about eye evolution.
Source:
Sinclair, Kai. 2017. Watch the secret to a squid’s crystal clear underwater vision. Science (10 August).
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