turns out chitons have crystal eyes
Chitons (in case y'all don't already know) are molluscs with awesome jointed shells vaguely resembling a trilobite. Some of the most awesome eyeballs on the planet are grown by molluscs, namely squid and octopi, which have eyes wired the right way around, as opposed to our own, backwards-wired eyes (I mean really, if you were designing a light sensor, would you run the wires over the receiver, or behind it?). But all those eyes have lenses made of proteins (which can become cataractic when the proteins break down, or suffer oxidative or glycemic damage), and these guys have lenses made of clear calcium carbonate crystal.
I wonder how well they see? Why does nothing bigger have crystal eyes? They won't be at all able to accomodate, so any focusing would have to be all in changing the distance between the lens and the retina, rather than adjusting the lens shape like we do. They might not focus much at all (I mean, it's not like they're racing around, and need to see to navigate), but reacting to movement or shapes above them is enough to get a warning to clamp down on the rock.
Anyway, so cool I had to share. I hope I see them on the beach, when I'm working as a beach naturalist with the aquarium this summer! I'll have one more thing to tell folks about them :)
I wonder how well they see? Why does nothing bigger have crystal eyes? They won't be at all able to accomodate, so any focusing would have to be all in changing the distance between the lens and the retina, rather than adjusting the lens shape like we do. They might not focus much at all (I mean, it's not like they're racing around, and need to see to navigate), but reacting to movement or shapes above them is enough to get a warning to clamp down on the rock.
Anyway, so cool I had to share. I hope I see them on the beach, when I'm working as a beach naturalist with the aquarium this summer! I'll have one more thing to tell folks about them :)