A new study shows that some silvery fish (herring and sardines) are breaking a basic law of physics: the law of reflection. Researchers from the University of Bristol found that this adaptation has helped them evade predators.
Reflective surfaces, like the bodies of these fish, polarize light. When light polarizes, its reflectivity drops. In the ocean, this would make fish, like herring, easier to spot.
The researchers found that the fish’s skin, which typically contains only one type of guanine crystal (responsible for producing the pearly, iridescent look), actually contained two different types, each with different properties.
Had the fish only contained one type, the light would fully polarize, causing a decrease in reflectivity. However, the combination means the fish’s skin does not polarize the reflected light, allowing it to remain highly reflective.
“We believe these species of fish have evolved this particular multilayer structure to help conceal them from predators, such as dolphin and tuna,” explained Dr. Nicholas Roberts from Bristol’s School of Biological Sciences.
“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.”
To learn more:
- Read the full press release from Bristol: How a fish ‘broke’ a law of physics
- Find the results, published in the journal Nature Photonics, here: Non-polarizing broadband multilayer reflectors in fish
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