For the first time in the scientific record, squid have been observed changing their coloration to blend into their surroundings. You might wonder how it took the scientific community so long to catch a glimpse of this behavior, but when you see how good it is it becomes easier to understand how nobody spotted it sooner.
Octopuses and cuttlefish were previously believed to be the only cephalopods capable of camouflaging into surrounding substrate, but a study published in Scientific Reports has now added squid to the roster. The discovery came about in a lab setting where researchers observed the animals trying to blend into the color of their enclosure.
“Squid usually hover in the open ocean but we wanted to find out what happens when they move a bit closer to a coral reef or if they’re chased by a predator to the ocean floor,” explained one of the three first authors, Dr Ryuta Nakajima, OIST visiting researcher, in a statement.
Their open ocean nature has meant that few have had the opportunity to study squid behavior on the seafloor, and the difficulty in keeping them alive had prevented much in the way of lab experimentation too.
However, back in 2017 scientists overcame this problem by culturing a species of oval squid known locally as Shiro-ika. It’s one of three oval squids in the waters off Okinawa, Japan, but the animals used for the research were bred to tolerate captivity.
As for their camouflage, the finding came about as something of a happy accident as often happens in scientific discovery. Researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) were cleaning out their tanks which had grown a bit of algae.
On closer inspection, they noticed that when the squid were swimming over the algae, they turned a darker color whereas in other parts of the tank they were lighter. It was as if they were changing color to try and better blend in, something that hadn’t yet been officially recognized in squids.
Excited by the chance observation, the researchers conducted a controlled experiment to get a better idea of what was going on. In it, they left half a tank to develop algae while keeping the other half clean and set up cameras to observe what happened next.
Sure enough, the squid proved themselves to be quite the camouflage artists, flitting between dark and light colorations depending on where in the tank they were hanging out. While it was previously known that they could change color, they hadn't been observed using the skill in this way before now.
“This effect really is striking. I am still surprised that nobody has noticed this ability before us,” said another first author Dr Zdenek Lajbner. “It shows just how little we know about these wonderful animals.”
As well as bolstering the resume of oval squids, the finding demonstrates the importance of ocean floor environments for the survival of these animals, an understanding that could contribute to conservation research surrounding both life forms.
“If substrate is important for squid to avoid predation then that indicates that increases or decreases in squid populations are even more tied to the health of coral reef than we thought,” said Dr Nakajima.