The strange secret hidden within 200 bright eyes of a scallop – tech2.org

The strange secret hidden within 200 bright eyes of a scallop



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  The strange secret hideaway within 200 bright eyes of a scallop

Three of the eyes of the scallop Pecten maximus

Credit: Dan-Eric Nilsson, Lund University

Look at the meaty The scallops of the scallop, and behold, the scallop will look back: it has up to 200 bright and strange eyes, without giving any sign of what they think of you in their endless search for floating food particles.

Scientists have known since at least the 1960s, scallops use mirrors on the back of their eyes to reflect light forward and project images onto their double retinas. That was the work of Michael Land, a pioneer in animal vision research. But Land could never understand what those mirrors were made of, or how they worked; he supposed that crystalline guanine was involved, but all the microscopic techniques of the time dehydrated the reflected tissue, destroying his samples before he could study them.

  A close-up image reveals the strange blue eyes of a scallop.

A close Image above reveals the strange blue eyes of a scallop.

Credit: Matthew Krummins / CC BY 2.0

Now, in an article published on December 1 in the journal Science, a team of researchers from the Weizmann Institute of Sciences in Israel and the University of Lund in Sweden announce that they have deciphered the case.

Scientists instantly frozen the mirror tissue while studying it with a scanning electron microscope (this technique has the great name "cryogenic scanning electron microscopy" or "cryo-" SEM "). made of guanine crystals, but there was something strange and powerful about them. [Take our Vision Quiz: What Can Animals See?]

  This paper image shows the layers of flat and square crystals on the side.

This image of the paper shows the layers of flat and square crystals from a

Credit: Courtesy of Science

Guanine is not so rare in nature, it also appears in certain white spiders, the skin of chameleons and some small iridescent crustaceans, scientists have discovered.

But generally when guanine crystals are formed, they are formed as prisms, a not very good way to accurately reflect the light in a lens, and in scallops, That precision is important; the lenses in his eyes barely refract light, not even precise enough to focus an image.

  Cryo-SEM images reveal square guanine crystals within living cells in the eyes of a scallop.

Cryo-SEM images reveal the square guanine crystals within living cells in the eyes of a scallop.

Credit: Courtesy of Science.

The mirrors themselves make the focus for the scallops, and they do so by structuring and accurately shaping the guanine into the living tissue, the researchers found.

Each individual guanine crystal has the shape of a small square, not a prism. The squares are flat, grouped in curved and concave layers without any space between them; its flat, shiny fronts point directly to the creature's retinas.

Imagine a bunch of chessboards shaped like satellite dishes stacked on top of each other. Researchers compare the structure of these grouped crystals with the curves of reflecting telescopes, and it turns out to be a powerful focusing mechanism that allows each eye to train its attention in a different part of space.

How do scallops control crystal formation so finely? The researchers do not know yet.

Originally published in Live Science.

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