Cuttlefish, already known for their complex camouflage and communication, have been found to actively manipulate light polarization to attract mates. Male Andrea cuttlefish twist their arms in a way that creates a highly visible signal tuned to the unique vision of other cuttlefish, a discovery that highlights a previously unknown form of animal communication.
The Science of Polarization
Humans perceive light primarily through color and brightness, but light also has a property called polarization. It refers to the orientation of light waves, typically vibrating in multiple directions. Polarized light vibrates in a single direction, and cuttlefish eyes are uniquely adapted to detect this orientation.
Unlike humans, cuttlefish cannot see color well but can perceive properties of light beyond human capabilities, including polarization. They evolved this ability because the ocean environment itself is highly polarized, and they can use it to communicate.
How Cuttlefish Twist Light
Researchers at the University of Tokyo found that male cuttlefish use specialized arms to manipulate polarized light during courtship. These arms contain birefringent tissue, meaning they rotate the polarization of light by almost 90 degrees. This creates alternating bands of horizontally and vertically polarized light, which provides maximum contrast for cuttlefish vision.
The cylindrical shape of the arms is perfectly adapted to convert horizontal light into vertical, enhancing the signal’s visibility. The cuttlefish do not produce this polarization signal outside of mating displays, indicating it is an evolved behavior specifically for attracting a mate.
Implications and Future Research
This discovery shows that animal communication extends beyond color and sound to include properties of light invisible to humans. Just as animals use vibrant colors to attract attention, cuttlefish evolved to manipulate polarization, a hidden signal that remains undetected by most species.
The study raises further questions about whether cuttlefish use polarized light for other purposes beyond courtship. Scientists may need new tools and methods to explore the hidden visual world of these cephalopods and reveal additional forms of communication that remain unknown.
“Just as with the long-recognized and extensively studied diverse selection of animal coloration, there may be a similar diversity of polarization signals among polarization-sensitive animals – signals that remain entirely unknown to us because they are invisible to the human eye,” the researchers write.
