New State Of Matter Discovered in Chicken Eyes

Joseph Corbo and Timothy Lau, Washington University in St. Louis

The retina of the eye is home to rods and a variety of cones, which help the brain perceive color. When studying the retina of the chicken, researchers found that the five different types of cones are arranged in what is known as “disordered hyperuniformity” and has never before been seen in biology until now. The research was co-led by Salvatore Torquato and Joseph Corbo and was published in Physical Review E.

When a small section of the pattern is viewed, the position of the individual components (in this case, the different types of cones) appears to be random. On the large scale, there appears to be more some order to the perceived madness. This hyperuniform state of matter has been seen before in plasmas and liquid helium (which occurs at -269 degrees C, -450 degrees F) and allows the substance to act both as a crystal and a liquid.

Because the different types of cones are different sizes, this arrangement allows the retina to take on the crystal-like ability of maintaining the density throughout. However, all of the cones also have the same physical properties, just like a liquid. Chickens and other birds depend on acute eyesight, which is aided by their five types of photoreceptive cells that are densely packed into the retina. It is speculated that this ordered arrangement lends to the integrity of the retina while allowing them to perceive light and colors evenly.

Each type of cone has a set pattern that, when viewed individually, appears pretty obvious. When all of the patterns are put together, it has a very complicated order that is described as a “uniform disarray.” Each cone appears to have a zone around it which helps space out cones of the same type. This is a multi-hyperuniformity that has not been seen before, and the researchers believe it calls for a new state of matter to be used to describe it.

Beyond just being a neat fact about avian vision, disordered hyperuniformity is used to develop optical circuits which operate or restrict based on certain wavelengths. Now that this type of patterning has been found in a biological system, the field may be expanded in future research. Researchers hope that other scientists will go back and reexamine old data to determine if there are more instances of disordered hyperuniformity that may have gone unnoticed. 

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