Some cells, they discovered, were there to detect only touch, and responded to pressure. Another population of cells, called chemoreceptors, instead detected chemicals, such as those that imbued fish with flavor.
A series of genetic experiments then revealed that the surfaces of these taste-tuned cells were covered with different types of proteins, each tailored to its own chemical trigger. By mixing and matching these proteins, cells could develop their own unique tasting profiles, allowing the octopus’s suckers to discern flavors in fine gradations, then shoot the sensation to other parts of the nervous system.
It seems octopuses have “a very detailed taste map of what they’re touching,” Dr. Tarvin said. “They don’t even need to see it. They’re just responding to attractive and aversive compounds.”
Underwater, some chemicals can travel far from their source, making it possible for some creatures to catch a whiff of their prey from afar. But for chemicals that don’t move through the ocean easily, a touch-taste strategy is handy, Dr. Bellono said.
Discerning though it may be, the octopus palate hasn’t made these animals terribly picky. They eat fish, crabs, snails, other octopuses — “everything they can find, really,” Dr. van Giesen said. “They are voracious.”
The researchers weren’t able to investigate every chemical-sensing protein that played a role in octopus touch-taste tactics. But they found that some of the cells in the animal’s suckers would shut down when exposed to octopus ink, which is sometimes released as a “warning signal,” Dr. van Giesen said. “Maybe there is some kind of filtering of information that is important for the animal in specific situations,” like when danger is afoot, she said.