Cuttlefish are constantly reinventing themselves

Put a squid on the spot – or, to be more precise, a series of spots – and it will disappear. These relatives of the squid and octopus mimic the color and texture of their environment, camouflage themselves to blend in with seaweed, sand or stone, which helps them escape predators.

But no one knows exactly how a squid’s brain takes what the eyes see and gets the skin’s muscles to copy it. Do they watch their own skin as it changes and adapt it to the sand? Or what if getting the match doesn’t just depend on eyesight – does a certain kind of speck feel different to the animal than, say, stripes?

In an attempt to answer this question, scientists have used high-resolution videos that can show what individual skin cells do when a squid changes color.

In a paper published in the journal Nature on Wednesday, researchers found that squid sampled a wide variety of different options as they worked to make a match between their skin and their environment. As they got closer to a match, they repeatedly paused in their morphing, as if to check if they got it right this time. The findings are a glimpse into what’s going on in a fundamentally different form of life as it does something that seems almost magical to our eyes.

To match their background, cuttlefish use an array of pigment-filled skin cells called chromatophores and raised structures called papillae. Cuttlefish contract countless tiny muscles that open and close chromatophores, like pixels on a screen, to get the right pattern of whatever surface they swim over.

Extensive research has shown that squid can achieve their final pattern in less than a second. It was possible, thought Gilles Laurent, a professor at the Max Planck Institute for Brain Research in Germany and an author of the new paper, that the squid sees an image, decides how to mimic it, and then goes straight to a matching skin pattern. Dr. Laurent and his colleagues broke down that fraction of a second to observe which chromatophores opened and closed on their way to the final product.

For the study, the team presented 30 cloth-printed backgrounds to squids, rolling out the backgrounds on the bottom of their aquarium. As the animals changed color and pattern, the cameras watched, and when the researchers analyzed the data, they saw that each squid worked through different patterns.

“What we observe is that the animals slowly move toward that end pattern intermittently, in segments of movement, interrupted by moments where they stop and seem to compare themselves to the end goal they want to reach,” said Dr. Laurent. “Ultimately, when they achieve something that satisfies them, they stop.”

The small pauses get longer as the squid gets closer to the final target, he continued. It may become more difficult for the squid to determine whether its skin pattern requires additional changes.

“We believe they have some knowledge of the pattern they are expressing at any given time,” he said. “How that is, we do not know.” They may use their eyes to check their coloration. But it could also be that the squid is pursuing a certain feeling in its skin. No one is sure of the answer.

In addition, the team of Dr. Laurent noticed that when a squid encountered a backdrop it had seen before, it didn’t interact with it in exactly the same way. The squid took a different route each time to its final pattern.

That suggests the animals don’t learn a strategy to reach a goal the way humans do when they learn to walk or pick up objects, said Dr. Laurent. Instead, they are somehow born with the ability to paint what they see onto their skin using thousands of tiny muscle contractions.

“It’s so strange to us, as a motor system, as a behavior, as an animal,” he said. “These are just amazing creatures.”

This system, honed over centuries of evolution, can turn out to be quite complicated or deceptively simple. Only more research will bring scientists closer to understanding the experience of a squid as it flashes across mottled sand, bends its skin and disappears.