Cephalopods – octopuses, squid, and their kin – are marine masters of disguise. The tentacled animals can blend seamlessly into their environment, matching not only the color, but also the texture of nearby objects in the water around them. To explain how these skin-changers manage such a feat, PBS and KQED San Francisco’s DeepLook is taking us up-close-and-personal with one such beastie: the market squid.
It’s plain to see why the market squid got it’s Latin name, Doryteuthis opalescens. Like their namesake mineral, waves of color flit across the squids’ bodies as they move from place to place. Cephalopods rely on chromatophores – tiny, pigment-filled cells in their skin – to create these waves.
Each chromatophore contains an elastic sac filled with pigments, which are typically black, brown, orange, red, or yellow. When pulled taught, the pigments within are exposed to light, and appear brighter. When loosened, the pigment is moved away from surrounding light, causing the color to fade. You can think of this like a partially-inflated balloon filled with paint: if you were to squeeze the balloon, the paint would be pushed towards the surface, stretching the latex thin, and exposing the paint’s color.
But market squid don’t stop there. They can also change how iridescent they are using light-reflecting cells called iridophores. “They can actually mimic how sunlight filters down from the surface, allowing them to hide in plain sight in the open ocean,” says DeepLook host Amy Standen.
We know that cephalopods have a complex system of nerves and muscles, but just how they manage to make such quick changes to their appearance remains something of a scientific mystery. Is this a voluntary action, controlled by the squid’s brain? Or are the skin cells reacting on their own? To find out, researchers at Stanford University began snipping the nerve that connects the brain to the chromatophores on one side of the squid’s body. Initially, this caused the cells to stop firing, but after a few days, the chromatophores on the paralyzed side started working again.
The team even observed working cells in skin that had been removed from the squid’s body, and thus, completely disconnected from the brain. “This suggests that color change might be a bit like breathing,” explains DeepLook. “Something we can either choose to do, or do automatically. Only, it’s even cooler because color changing requires an awareness of your surroundings. And in these animals, that awareness is spread throughout the skin.”
We still don’t know for sure, but you can follow along as the research progresses on the project blog. Nature, you crazy.
IMAGES: KQED/PBS Studios