Monday, December 3, 2012
SIlvery Fish Elude Predators with Light-Bending
It has been found in a new study that fish with a silvery coloring have developed a way to become basically invisible to predators. At practically every angle these colored fish are able to use the make up of their skin to camouflage themselves into their surrounding, protecting them from any near predators. Like the many adaptations we read about in The Making of the Fittest, silver fish like sardines and Atlantic herring have become the "masters of camouflage" with this new adaptation.
Dr. Nicholas Roberts, one of the authors of the study, believes these fish have the ability to work their way around a basic reflection law. This law states that whenever light is reflected off a surface, the resulting light that comes off of this surface becomes polarized. Silver fish have the ability to avoid such polarization with the different makeup of their skin. Their skin is composed of alternating layers of cytoplasm and two different types of guanine crystals. These guanine crystals refract light, which is key in their invisibility process. They contain different refractive indexes, allowing the fish to create a unique reflective property.
Dr. Roberts explains that "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." This details how the fish are able to have such a capability and explains what seems to be an observation of invisibility as something more controllable. Silver fish have evolved over time to contain the exact ratios of the two types of guanine and have achieved near-constant reflectivity because of this. The invisibility mechanism is seen in all silvery fish.