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Octopuses Use Their Suckers to Taste by Touch

Advanced eyesight. The ability to shoot ink to elude prey. Now researchers have added tasting by touch to the list of amazing characteristics of the common octopus.

(CN) — New research sheds new light on how octopuses taste by touch, a biological feat that researchers say makes it possible for the eight-armed ocean dwellers to navigate the perils of the seafloor.

Of the millions of countless creatures that inhabit Earth’s oceans, the octopus stands in the eyes of many as one of the most fascinating. From their eight highly flexible arms for which they’re named to their famed ability to eject black ink from their bodies to escape potential predators, octopuses come equipped with a host of characteristics that have enthralled marine biologists for years.

One area of interest to researchers is the octopus’ complex nervous and sensory systems. On top of advanced eyesight and motor skills, octopuses also have the unique ability of being able to taste through their sense of touch, an ability made possible by the suckers on their numerous arms.

While experts have been aware of this extraordinary ability, questions have long swirled around the subject. In a new study published Thursday in the journal Cell, researchers report that they may have helped to answer some of those questions.

Experts began this research effort by experimenting with the California two-spot octopus, a common octopus species native to the Pacific Ocean. Researchers determined an octopus will exhibit completely different behaviors whenever one of its suckers touched prey rather than non-prey object, a behavioral change the researchers say confirms the existence of this touch-taste ability.

This confirmation pushed researchers to study the octopus suckers themselves to understand what allows them to perceive taste. They found the suckers are equipped with subtle clusters of sensory cells that give an octopus the ability to experience more than just touch when those cells are being put to work.

What researcher still don’t understand, however, is how exactly this information coming in from the suckers works with other stimuli and signals that an octopus is exposed to. Researchers not only want to know how this relationship exists, but also how this relationship influences octopus behavior, such as how an octopus decides to grab whatever it touches and tastes.

Nicholas Bellono, a molecular and cellular biologist at Harvard University and one of the authors of Thursday’s study, said that while there is still much more to learn on the subject, a unique information filtering system that pairs well with the complex nervous system of octopuses could possibly answer some of these questions.

"We also showed that separate and distinct chemo- and mechanosensory cells express specific receptors and exhibit discrete electrical activities to encode chemical and touch information, respectively," Bellono said with the release of the study. "Our results demonstrate that the peripherally distributed octopus nervous system exhibits exceptional signal filtering properties that are mediated by highly specialized sensory receptors."

Researchers also explored how special chemicals known as terpenoids play a role in an octopus’ sense of taste-touch. Their data suggests these chemicals work in the sensory cells in octopus suckers to encourage different octopus reactions based on what it is touching, giving octopuses and other marine invertebrates access to a kind of a early detection warning system when they come into contact with something toxic. This detection system not only makes it easier for octopuses to find healthy food supplies, but also helps them navigate the depths of the ocean safely.

One thing researchers did not explore in this research effort was how this sensitive touch-taste sense could be influenced by changes in water temperatures, such as those brought on by climate change, but researchers note that such a relationship could be explored in future studies.

“We have not explored temperature sensation or how it affects the ‘taste by touch’ sense,” Bellono said in an email. “It is entirely possible that temperature regulates octopus chemotactile sensation or that the octopus uses distinct thermosensors for exploration.”

Researchers also hope to learn more about how this touch-taste sense is experienced by other cephalopods like squid, to see how their unique tentacle method of entrapping prey works with a touch-taste sense when compared to octopuses.

Bellono and the research team say these questions and more need to be explored moving forward, and that it will only be through continued research efforts like theirs that experts will better understand the complexities behind the lives and senses of these eight-armed underwater mysteries.

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