Do Clams Have Eyes?

[Reef head]

Hahahahaha.

Good to know.

 

[vlangel]

I've looked at those little bumps on my clams mantle and wondered about them. Thanks, now I know.

 

[Velodog2]

Slightly off topic but I love this theory of how simple it can be for an eye to evolve, and why so many apparently have done so independently of each other. I always think of this when simple eyes come up as a topic.

Any photosensitive molecule can function as a shadow detector. Many molecules in animals are photosensitive to some extent.

If a patch of photosensitive molecules being used as a shadow detector happens to sit in a slight depression in the surface of an animal, it is possible for it to also tell what direction light is coming from. A deeper depression and a smaller opening makes this work better.

If eventually the opening to the eye "pit" becomes small enough, it can function as a pin hole camera and actually begin to form images. If that opening is covered by a thin layer of tranlucent or transparent tissue, you have a rudimentary eyeball.

It's a lot of evolution to go from there to a fully functioning eye, but you can see once the ball has started rolling each change can confer advantages to the organism and the ball keeps rolling as long as that remains true. A elegant thought experiment in the field of evolution.