First time recording a squid that changes color according to the environment

Japanese scientists discovered that squid can change color in a split second to hide in its surroundings, in order to evade predators.

Previously, only two groups of cephalopods, octopuses and cuttlefish, were known to be able to camouflage themselves into their surroundings by changing body color. However, a new study published in Scientific Reports last week adds squid to the list.

The discovery was made in a laboratory by biologists from Japan's Okinawa Institute of Science and Technology (OIST). It opens up new avenues for research into how squids see and perceive the world around them, which can contribute to conservation efforts.

Squid in the wild prefers to live in the open ocean, where their light skin color blends perfectly with the clear water and glimmer of sunlight above. Therefore, very few people have the opportunity to observe the behavior of squid on the sea floor. The creature's difficult nature to keep in captivity also makes laboratory research difficult. That is why scientists did not know about their ability to change color until now.

The OIST's discovery came by chance when researchers were cleaning the bottom of an aquarium in the lab, where they were raising a local species of squid called Shiro-ika. It is one of only three species of oval squid (leaf squid) found in the waters off Okinawa.

This squid has different dark and light colors in different parts of the tank with different algae density.

When they closely observed the squids at the bottom of the tank, they discovered that they had different dark and light colors in the parts of the tank with different algae densities. Intrigued by this, the team conducted a controlled experiment to better understand what was going on. In it, they cleaned half of the tank and covered the other half with algae, then set up a camera to observe what happened next. The result was as expected, Shiro-ika squid changed its body color quickly from light to dark when swimming from the clean tank to the algae tank and vice versa.

"The effect is really dramatic. I'm surprised no one has noticed it before," said Dr. Zdenek Lajbner from OIST, first author of the study. "It shows how little we know about marine animals like squid."

The new discovery has implications not only for the squid but also for the ecosystems in which they live. Lajbner believes that if the surrounding environment is important for squid camouflage, the increase or decrease in numbers of this group of cephalopods may be related to the health of the reef.