Biological Cloaking of Silver Fish

Brighter is not always better, especially for silvery fish needing to evade predators. Yet sardines and herring flourish. Researchers from Bristol’s School of Biological Science have discovered their secret—a cloaking “technology” that twists the laws of physics to their advantage.

Normally, when light reflects off a shiny surface it becomes polarized, with the light waves all aligned to match the surface off which they bounced. That’s why a smooth water surface can produce such a glare. Silvery fish are shiny because they have multiple layers of reflective guanine crystals in their skin. Yet they don’t announce their presence to predators with a similar flashy glare because their skin takes photonic science a step further.

There are actually two different kinds of guanine crystals in these reflective layers. Each kind of crystal has a different “refractive index,” the property that determines the angle at which light is reflected. Thus, as light is perfectly reflected from each kind of crystal, the combined reflection contains light waves that are not all aligned. Hence, there is perfect reflection without polarization and without glare. Instead, the fish seem to match and mirror their environment, remaining virtually hidden in plain sight.

Silvery fish like these herring, though highly reflective, are able to hide from predators in plain sight thanks to the unique optical properties of their skin. Image by Jacob Bøtter, via Flickr under creativecommons.org.

“We believe these species of fish have evolved this particular multilayer structure to help conceal them from predators, such as dolphin and tuna,” explains Dr. Nicholas Roberts, coauthor of “Non-polarizing broadband multilayer reflectors in fish” published in Nature Photonics. “These fish have found a way to maximize their reflectivity over all angles they are viewed from. This helps the fish best match the light environment of the open ocean, making them less likely to be seen.”

This natural “cloaking technology” could be the biomimetic clue leading to improved optical devices. “Many modern day optical devices such as LED lights and low loss optical fibres use these non-polarizing types of reflectors to improve efficiency. However, these man-made reflectors currently require the use of materials with specific optical properties that are not always ideal,” explains lead author Tom Jordan. “The mechanism that has evolved in fish overcomes this current design limitation and provides a new way to manufacture these non-polarizing reflectors.”

Fish with better camouflage would have a selective advantage favoring survival, but fish possessing this feature are just a variety of fish.

Biomimicry is the science of copying designs and processes found in nature to produce technological innovations. Evolutionists consider such amazing designs to be evolutionary success stories. Fish with better camouflage would have a selective advantage favoring survival, but fish possessing this feature are just a variety of fish. Nothing about this discovery indicates that the silver fishes’ optical twist on physics came about through molecules-to-man evolution. God created the principles of physics by which the world operates as well as all kinds of life in it. And if inventors are able to imitate the principles behind the shiny fishes’ cloaks to produce better optical devices, they will not be imitating evolution but rather making use of one of God’s designs. The evolutionary insistence that designs like this are the products of time, chance, and the laws of nature (the only factors in blind, purposeless, directionless evolution) ultimately is an attempt to rob God of His glory. This discovery, like many others, instead reveals the creative and artistic genius of our glorious Creator.