Their very own Invisibility Cloak
In a recently published study in 'Nature' (Source 1 & 2),
scientists have discovered how certain silvery fish can camouflage and
make themselves invisible to predators from nearly every angle.
When light is reflected from a surface, it usually will become
polarized. Hence, it was assumed before that the fish's skin would
fully polarize light when reflected, so
there
would be a drop in overall reflectivity, which would make the fish more
visible to predators. And to hide from predators, a near-constant
reflectivity is needed or else the fish appears to be more visible.
Now, in case of silvery fish the skin is highly layered. After removing
the outermost layer i.e. its scales, the silvery sheen still remains.
But underneath the scales there is the layer known as the "stratum
argenteum", that consists of guanine crystals and cytoplasm. The
guanines crystals are of two types and they are responsible for
refracting light. These two types of crystals have different refractive
indexes that create a unique reflective property.
“The
polarization happens over a range of angles instead of one, and the end
product of having all the layers together is that it creates a
polarization-neutral reflector,” Dr. Nicholas Roberts, one of the
researchers, said. (Source 3).
Over their evolutionary course,
the silvery fish have evolved a perfect ratio of the two guanine
crystals for a near-constant reflectivity and thus it has helped them
evade predators.
Also, according to the researchers, this mechanism is common in all silvery fish.
Source:
1) http://www.nature.com/nphoton/
2) http://www.nature.com/nphoton/
3) http://www.nytimes.com/2012/
4)http://physicsworld.com/cws/
Image credit: Jeffrey L. Rotman/Getty Images
Their very own Invisibility Cloak
In a recently published study in 'Nature' (Source 1 & 2), scientists have discovered how certain silvery fish can camouflage and make themselves invisible to predators from nearly every angle.
When light is reflected from a surface, it usually will become polarized. Hence, it was assumed before that the fish's skin would fully polarize light when reflected, so
In a recently published study in 'Nature' (Source 1 & 2), scientists have discovered how certain silvery fish can camouflage and make themselves invisible to predators from nearly every angle.
When light is reflected from a surface, it usually will become polarized. Hence, it was assumed before that the fish's skin would fully polarize light when reflected, so
there
would be a drop in overall reflectivity, which would make the fish more
visible to predators. And to hide from predators, a near-constant
reflectivity is needed or else the fish appears to be more visible.
Now, in case of silvery fish the skin is highly layered. After removing the outermost layer i.e. its scales, the silvery sheen still remains. But underneath the scales there is the layer known as the "stratum argenteum", that consists of guanine crystals and cytoplasm. The guanines crystals are of two types and they are responsible for refracting light. These two types of crystals have different refractive indexes that create a unique reflective property.
“The polarization happens over a range of angles instead of one, and the end product of having all the layers together is that it creates a polarization-neutral reflector,” Dr. Nicholas Roberts, one of the researchers, said. (Source 3).
Over their evolutionary course, the silvery fish have evolved a perfect ratio of the two guanine crystals for a near-constant reflectivity and thus it has helped them evade predators.
Also, according to the researchers, this mechanism is common in all silvery fish.
Source:
1) http://www.nature.com/nphoton/
2) http://www.nature.com/nphoton/
3) http://www.nytimes.com/2012/
4)http://physicsworld.com/cws/
Image credit: Jeffrey L. Rotman/Getty Images
Now, in case of silvery fish the skin is highly layered. After removing the outermost layer i.e. its scales, the silvery sheen still remains. But underneath the scales there is the layer known as the "stratum argenteum", that consists of guanine crystals and cytoplasm. The guanines crystals are of two types and they are responsible for refracting light. These two types of crystals have different refractive indexes that create a unique reflective property.
“The polarization happens over a range of angles instead of one, and the end product of having all the layers together is that it creates a polarization-neutral reflector,” Dr. Nicholas Roberts, one of the researchers, said. (Source 3).
Over their evolutionary course, the silvery fish have evolved a perfect ratio of the two guanine crystals for a near-constant reflectivity and thus it has helped them evade predators.
Also, according to the researchers, this mechanism is common in all silvery fish.
Source:
1) http://www.nature.com/nphoton/
2) http://www.nature.com/nphoton/
3) http://www.nytimes.com/2012/
4)http://physicsworld.com/cws/
Image credit: Jeffrey L. Rotman/Getty Images
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