With their mesmerizing intelligence, ever-changing skin, and soft bodies powered by three hearts, octopuses are among the most captivating creatures in the ocean. These “sea aliens” possess an extraordinary ability to blend seamlessly into their surroundings, thanks to their camouflage skills. But there’s more: octopuses can also taste their environment using their arms, a discovery that adds another layer to their already impressive list of talents.
How Do Octopuses Taste With Their Arms?
As octopuses explore the seafloor, their arms, equipped with thousands of independently moving, finger-like suckers, play a crucial role. These suckers aren’t just for gripping or manipulating objects; they are sensory powerhouses that can both touch and taste their surroundings. This unique ability is made possible by specialized cells in the suckers’ skin.
Researchers led by molecular biologist Lena van Giesen at Harvard University have identified these chemosensory cells in the California two-spot octopus (Octopus bimaculoides). These cells are akin to our own taste and smell receptors, capable of detecting molecules through direct contact, much like the way our tongues taste food.
The Science Behind the Taste-Touch Sensation
The chemosensory cells in the octopus’s suckers have thin, branched ends and can signal continuously, a process known as tonic firing. However, they need to be in close contact with their target, much like our tongues need to touch food to taste it. These cells can respond to various “flavors,” including chemicals found in cephalopod ink and warning signals from potentially toxic prey.
“This ability is incredibly useful for octopuses, allowing them to detect prey hidden within seafloor crevices or areas inaccessible to their traditional sense organs,” explains Nicholas Bellono, a molecular biologist involved in the study.
In addition to chemosensory cells, the team also discovered mechanosensory cells in the suckers’ skin. These cells, which have stubby, branched ends, fire signals only at the start of contact (phasic firing), helping the octopus distinguish between inanimate objects and live, squirming prey.
A Remarkable Sensorimotor System
The researchers observed that octopuses use specific touch motions that vary depending on the type of molecules triggering the chemotactic receptors. By studying the animals’ behaviour and analyzing the proteins expressed by genes in the sucker cells, they uncovered more about how this touch-taste ability works.
For instance, some chemotactic cells showed a strong response to fish and crab extracts, suggesting that this ability isn’t just for detecting prey but also for avoiding danger. Octopus ink, for example, can temporarily shut down the limb’s ability to taste, possibly as a defence mechanism.
“Our findings were surprising because aquatic chemosensation has long been associated with distant waterborne signals via dissolved chemicals,” says Bellono. “Our study shows that octopuses, and potentially other aquatic animals, can also detect poorly soluble molecules through direct contact.”
The Evolutionary Mystery of Octopus Taste-Touch
The genes responsible for these chemotactic receptors were found in three different octopus species examined by the researchers. However, other cephalopods, like squid, do not appear to use their suckers to taste their environment in the same way, suggesting that this sensory system may be unique to octopuses.
Biologist Rebecca Tarvin from the University of California, who was not involved in the study, is intrigued by how this unique sensorimotor system evolved. The team is now exploring many questions related to its evolution, physiology, and use.
While the researchers have closely examined only a few genes related to these specialized taste cells, there are hints of a much larger network of sensation-related genes in the octopus genome that have yet to be fully understood.
A Marvel of Nature
The octopus’s arms, with their mini “brains” and highly specialized receptors, are capable of filtering vast amounts of sensory information. This may explain why two-thirds of an octopus’s neurons are located in its arms, enabling them to act semi-independently of the main body.
In essence, octopuses have eight intelligent, dexterous arm-tongues that allow them to feel and taste their way through the dark depths of the ocean. This fascinating ability adds to the already strange and wonderful world of octopuses, showing just how delightfully weird life can get.
This groundbreaking research was published in the journal Cell.
