For an animal that doesn't really do much except be delicious, it has an amazing set of eyes.
In the 1960s, biologist Michael Land showed that each scallop eye — it has up to 200 of them, each about a millimeter in diameter — uses a mirror to focus light into images, while most other eyes use lenses. That natural mirror is made of crystals of guanine, Land determined — better known for its job as one of the four nucleotides that make up DNA. Now, cryo-electron microscopy is bringing those blueprints out of their shell, researchers report in the Dec. 1 Science.
For one thing, the guanine crystals that build the scallop’s eye mirror are perfectly square... Guanine doesn’t form crystal shapes that evenly pack together in the lab. That means that, somehow, the scallop is controlling the crystallization process. The square crystals fit together edge-to-edge like bathroom tiles to form a smooth surface that minimizes image distortion.
A single layer of this guanine mosaic is transparent. But each scallop eye stacks up 20 to 30 of these tiled sheets to create a reflective surface. The whole contraption is something like a telescope that pieces together hexagonal mirrors into one giant curve.
And the scallop’s eye mirror isn’t shaped like a perfect hemisphere, the researchers found. Instead, the mirror has an unusual 3-D shape that allows the scallop to focus light on one of two retinas, depending on the angle of the incoming light. One retina is tuned to dimmer light coming from the peripheral vision; the other best captures movement in bright light.
https://www.sciencenews.org/article/scallops-amazing-eyes-use-millions-tiny-square-crystals-see
No comments:
Post a Comment
Due to a small but consistent influx of spam, comments will now be checked before publishing. Only egregious spam/illegal/racist crap will be disapproved, everything else will be published.