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Scallop Eye

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发表于 12-5-2017 16:11:51 | 显示全部楼层 |阅读模式
本帖最后由 choi 于 12-5-2017 16:14 编辑

(1) Carl Zimmer, The Scallop Sees with Hundreds of Space-Age Eyes; The tiny structures resemble complex reflector telescopes, researchers report. New York Times, Dec 5, 2017.
https://www.nytimes.com/2017/11/30/science/scallops-eyes.html

Quote:

(a) In scallop: "Arrayed across the opening of its shell, the eyes * * * Each [eye] sits at the tip of its own tentacle and can be extended beyond the rim of the shell.

(b) "Now, a team of Israeli researchers has gotten a look at the hidden sophistication of the scallop eye, thanks to powerful new microscopes ['cryo-electron microscope'; actually it should be cryo-electron microscopy -- the same electron microscope, but using a new technique: with cryo or freezing; 'new' is relative, maturing in the last decade and whose inventors received Nobel prize in chemistry this year]. On Thursday [of last week, Nov 30], they reported in the journal Science that each eye contains a miniature mirror made up of millions of square tiles. The mirror reflects incoming light onto two retinas ['which are mostly transparent'], each of which can detect different parts of the scallop's surroundings.

"Our own eye has been likened to a camera: it uses a lens to focus light on the retina. The new research suggests that scallop eyes are more akin to another kind of technology: a reflector telescope of the sort first invented by Newton. Today, astronomers build gigantic reflector telescopes to look in deep space, and they also build their mirrors out of tiles.

(c) "Benjamin A Palmer, a postdoctoral researcher at the Weizmann Institute of Science in Israel: is the first author of the scientific report.

(d) "guanine. It's best known as one of the main ingredients of DNA, but in some animals guanine is packed into crystals that reflect light.

"Some fish have a silvery tint to their scales thanks to guanine crystals. Chameleons use guanine crystals to help them change the color of their skin. But no one knew how guanine helped scallops to see.

"Using cryo-electron microscopes, Dr. Palmer and his colleagues discovered that scallops make a kind of guanine crystal never seen before in nature: a flat square. “We were amazed,” he said. “We knew this would be something cool.”

"The researchers found that the mirrors are made of twenty to thirty layers of guanine, each containing millions of squares

(e) "Paradoxically, the guanine squares don’t reflect light on their own — they’re transparent. But [together] their arrangement turns them into a collective mirror.

My comment:
(a) If you do not understand what the NYT is saying, It is quite all right. Neither did I upon ereading it. Read on.
(b) The NYT report says, "NASA has built X-ray detectors to study black holes that mimic lobster eyes."
(i) I am unwilling to digress, but it is also important to know how lobster eye works.

Harun Yahya, The Design In Nature. London: Ta-Ha Publishers Ltd, 2004, at pages 11-12
https://books.google.com/books?i ... %20tube&f=false
("We are accustomed to the camera-type eye found in vertebrates. * * * A lobster's eye works on a principle of reflection rather than that of refraction. The most outstanding characteristic of the lobster eye is its surface which is composed of numerous squares.  * * * These well-arranged squares are in fact the ends of tiny square tubes forming a structure resembling a honeycomb. At first glance, the honeycomb appears 6to be made up of hexagons, although these are actually the front faces of hexagonal prisms [This is confusing, but the preceding sentence talked about bees' honeycomb, emphasizing on tubes -- not lobster's eye]. In the lobster's eye, these are the squares in place of hexagons.  Even more intriguing is that the sides of each one of these square tubes are like mirrors that reflect the incoming light. The reflected light is focused onto the retina flawlessly. The sides of the tubes inside the eye are lodged at such perfect angles that they all focus onto a single point")
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 楼主| 发表于 12-5-2017 16:13:31 | 显示全部楼层
(2) Amanda Johnson, Scallop Eyes Mirror Reflecting Telescopes. American Association for the Advancement of Science (AAAS; publisher of Science magazine), Nov 30, 2017
https://www.aaas.org/news/scallo ... flecting-telescopes

Note:
(a) neon tetra
https://en.wikipedia.org/wiki/Neon_tetra
(freshwater; native to Amazon basin)
(b) tetra
https://en.wikipedia.org/wiki/Tetra
("Tetra is no longer a taxonomic, phylogenetic term. It is short for Tetragonopterus, a genus name formerly applied to many of these fish, which is Greek for 'square-finned' (literally, four-sided-wing)" )

(3) Here is the scientific report:
Palmer BA et al, The Image-Forming Mirror in the Eye of the Scallop. Science, 358: 1172-1175 (Dec 1, 2017).
http://science.sciencemag.org/content/358/6367/1172.full

My comment:
(a) You are unable to read it for free. It is sufficient to search images.google.com with (scallop eye tiles 2017), which will show a black-and-white photo of an scanning electron microscope displaying tiles that constitutes the mirror/inner surface of the a scallop eye.
(b) The new findings in this scientific report are manifold. One of which is to explain why there are two retinas in one scallop eye. The most recent report-- and in history, there were few than a handful of scientific reports to explore existence of two retinas -- said one one was functional (in focus). See (n)(ii) right below.
(i) BUT first, you must know how the two retinas in AN scallop eye are positioned. View Figure 1 in
Speiser DI et al, Spectral Sensitivity of the Concave Mirror Eyes of Scallops: Potential Influences of Habitat, Self-Screening and Longitudinal Chromatic Aberration. Journal of Experimental Biology, 214: 422-431 (2011)
http://jeb.biologists.org/content/214/3/422
(proximal and distal retinas)

The light enters top to bottom, is reflected by the mirror, and bounced straight back to transparent retinas.
(ii) Speiser DI et al, Examining the Effects of Chromatic Aberration, Object Distance, and Eye Shape on Image-Formation in the Mirror-Based Eyes of the Bay Scallop Argopecten irradians. Integrative and Comparative Biology, 56:796-808 (2016).
https://www.ncbi.nlm.nih.gov/pubmed/27549200

(4)
(a) At last, about telescopes. There are three types, but we are concerned about two: refracting and reflecting.

Types of Telescopes and Their Advantages and Disadvantages. Telescope Review Online, undated.
https://telescopereviewsonline.c ... -and-disadvantages/

Only view diagrams  (because it does not explain well about the good, the bad, and the ugly).  One can see human eyes are of refracting type; scallop eye are reflecting. Lobster eye is also reflecting, but different in principle from that of scallop eye.
(b) reflecting telescope
https://en.wikipedia.org/wiki/Reflecting_telescope
(section 2.1)

Refracting telescope is easier to maintain than the reflecting one, because the former is structurally simple whereas the latter has a mirror in the middle of telescope tube, which is easily dislodged.

(5) Still we do not know what a scallop see: blurred or sharp vision, black-and-white or colored (though a scientific report said that in molecular level, scallop does not have light receptor for color, and questionable whether it has light receptor for human black-and white vision).
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