How Octopuses Taste by Touch

News

The Context: Scientists have long known that octopuses are able to taste what they touch with their tentacles, but the way their tentacles sense taste has not been well understood.

The Study: Octopuses use cells called chemotactile receptors to taste what they touch, finds a new study in Cell by NYSCF – Robertson Neuroscience Investigator Nicholas Bellono, PhD, of Harvard University.

The Importance: The results shed light on the unique sensory system of the octopus and lay groundwork for future studies on the evolution of sensory systems across different animals.


For an octopus, tentacles do more than capture food: they taste it too. Dr. Bellono’s team aimed to find out how octopus arms carry out this special feat.

Tasting Prey

When an octopus finds a potential meal, it reaches out to touch it. If it approves of what it tastes, it sweeps the prey into its mouth. 

To take a closer look at this behavior, the team offered octopuses either a tasty crab or an inanimate object. The octopuses touched both the objects, but they only gobbled down the crab.

The scientists then examined the suckers lining the octopus’s tentacles and discovered specialized ‘chemosensory’ cells that detect chemicals emitted by whatever they are touching. Additionally, ‘mechanosensory’ cells on the suckers determine whether an object is moving or not. If an object is moving, then that lets the octopus know it could be a suitable meal and not a rock.

“This is highly useful for the octopus to detect prey hidden within seafloor crevices or areas inaccessible from its traditional sense organs,” Dr. Bellono, an Assistant Professor of Molecular and Cellular Biology at Harvard, told ScienceAlert.

Picking a Suitable Meal

Not all animals make for good meals for octopuses — some are toxic or dangerous. According to Dr. Bellono’s study, octopuses weed out these unwanted foods by sensing certain chemicals.

For example, the team found that chemoreceptors stayed dormant when octopuses were exposed to typical chemicals that spark smells or tastes in most animals. They only perked up in response to chloroquine, a chemical that tastes bitter to hum ans, and terpenoids — sometimes toxic molecules that are often released as a warning signal from ocean creatures like jellyfish or crabs. Upon detecting terpenoids, octopuses would typically withdraw and seek food elsewhere.

Evolutionary Underpinnings

Dr. Bellono hopes to continue exploring how octopuses evolved this unique system and whether other animals employ something similar.

“Could it be that in other cephalopods, they’re using similar receptors for distinct purposes, because the octopus explores with its arms and the sea floor, but the squid is in the open ocean and detecting greater distances and capturing with its chemicals which it extends out to grab prey?” Dr. Bellono posited to The Harvard Crimson. “It could be a really nice system to ask about evolutionary adaptation.”

“We’re trying to sample around natural products to see, what do the receptors detect? What do the animals detect?” he continued. “And then use those molecules as tools to understand how the receptors have evolved to suit that animal, detecting these ecologically relevant molecules.” 

Journal Article:

Molecular Basis of Chemotactile Sensation in Octopus
Lena van Giesen, Peter B. Kilian, Corey A.H. Allard, Nicholas W. Bellono. Cell. 2020. DOI: https://doi.org/10.1016/j.cell.2020.09.008

Read more in:

The New York Times

Business Insider

New Scientist

Cover image: An octopus attacks its prey.

Photo credit: Peter Killian

Diseases & Conditions:

Neurobiology

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