Caltech physicist Richard Feynman once said, "If you think you understand quantum mechanics, you don't understand quantum mechanics." It's possible the same could be said about cephalopods, the group of invertebrates that include octopuses, squid and cuttlefish. The last ancestor we shared with one of these animated Jell-O salads was probably a worm of some kind, so our DNA is basically nothing like theirs — not that they care. They didn't really do evolution the same way we did, but nevertheless managed to independently evolve into uncannily clever camouflage artists with large, complex brains, closed circulatory systems and camera-style eyes, just like ours ... well not just like ours.
The thing about cephalopods is, they've had 500 million years of independent evolution to figure out how to do things their own way. Any test you can create to measure something in a human — intelligence, say — isn't going to work for an octopus. Which is why neurobiologists studying cephalopods have jobs not unlike that of electricians figuring out the electrical grid on an alien planet.
"We've known for 50 years that the cephalopod brain is easily the most complex among invertebrates, and also that their dazzlingly intricate body patterning behavior is controlled by motor centers in the brain," says Dr. Sabrina Pankey, an evolutionary biologist in the Department of Molecular, Cellular, and Biomedical Sciences at the University of New Hampshire. "However, the neural architecture has been much more enigmatic."
Figuring out the neural bases of complex behaviors is inherently difficult in any animal, but trying to figure out how a squid can completely change its body patterning in a matter of milliseconds — or display one pattern to the squid on its left and another to the one on its right — is a sticky wicket, as you can imagine. One hypothesis has been that body coloration is organized in the cephalopod brain somatotopically — that one specific part of the central nervous system is solely responsible for controlling the patterning in a distinct patch of skin. That's how it works in our mammalian cortex, after all.
But a new study published in the Journal of Neuroscience shows, again, cephalopods aren't like us, and are in fact very not like us. The research team proposes its study subject, the oval squid (Sepioteuthis lessoniana), also known as the bigfin reef squid, achieves its skin patterning through mosaic organization — that these squid actually use multiple motor centers within the optic lobe of their brain to produce a single skin pattern like stripes, bands or spots. The fact that several parts of the brain work together at once to create a single display allows for greater complexity in the resulting pattern. It'd be like using multiple keyboards to write the same document, all at the same time. We vertebrates just don't do things that way.
Dr. Chuan-Chin Chiao, director of the Institute of Systems Neuroscience at the National Tsing Hua University in Taiwan and his co-author and student, Tsung-Han Liu, think that because several different areas of the optic lobe can be used to display single skin pattern in a specific body part — a dark mantle, stripe-y tentacles, polka-dot fins — the squid are able to flash up about 14 distinct patterns in the blink of an eye. We tend to think of redundancy as inefficient. But as cephalopods have overlapping parts of their brains to create specific patterns on specific body parts, meaning if one part of their brain is busy they can still flash information onto their bodies with awe-inspiring quickness.
Just think: If you had a bunch of different parts of your brain in charge of remembering a single word, your word-recall skills would be amazing.
"We think this research is particularly interesting because it shows how squids can efficiently modulate the expression of individual body pattern components, thus changing the appearance of their body color dynamically," said Chiao in an email. "This allows the squids to quickly switch different body patterns in visual communication. Thus, it is sort of like an alphabet visual language."
The researchers think the color patterns displayed by the squid are not only used as a communication signal to the same species, but are also used to hide or warn off other potential predators or prey. This research also highlights the fact that, though we vertebrates tend to think we've got the best systems for doing everything, cephalopods might be onto something, at least when it comes to efficient communication.
"The way these body patterns can be created, thanks to various combinations of brain centers activating, reminds me of word creation in agglutinative languages like German," says Pankey. "There is a linguistic mechanism to create compound words that then take on new meaning."
Maybe eventually we'll know enough about the cephalopod brain that we can find out whether squid learn "word" patterns by observation, or if it the information is hardwired, and whether different populations "speak" different patterns. But for now, the researchers are focusing on learning how visual information from the eyes regulates body patterning in the squids when they are communicating with each other in their natural environments.
"This will be much more difficult than anything we have shown so far," says Chiao.