Octopuses Use Suckers To ‘Taste’ Harmful Microbes

In this Science Friday episode, Flora Lichtman speaks with Harvard biologist Dr. Nicholas Bellono about how octopus arms function as highly sensitive sensors. The suckers host receptors that allow the animal to taste by touch, using insoluble environmental molecules and surface microbes to interpret its surroundings. Researchers demonstrate that microbes on crab surfaces influence octopus feeding decisions by producing signals that mark decayed prey as unpalatable. The conversation also reveals that a male arm used for mating, the hectocotylus, shares sensory receptors with the other arms, suggesting a broad chemosensory toolkit for tasks from feeding to reproduction. The discussion touches on the octopus’s impressive vision and the ongoing questions about color sensing in cephalopods, plus a lively look at other cephalopod superpowers.

Overview: The Octopus Arm as a Chemosensory Sensor

Octopuses rely on more than sight and suction to navigate their world. Dr. Nicholas Bellono explains that receptors exist in the suckers of the octopus arms, enabling a chemosensory sense that feels like taste by touch. These receptors bind environmental molecules, including insoluble compounds that cling to surfaces, and they help the animal gather information about what surrounds it as it explores cracks, crevices, and potential prey. What makes this discovery striking is that the octopus is not just tasting waterborne chemicals but actively sampling the texture-embedded molecular signatures that mark different habitats and organisms. This flavor of perception could help explain how octopuses decide whether a surface or item is safe to approach, eat, or avoid.

"the octopus is exploring by touch" - Dr. Nicholas Bellono

Microbes, Surfaces, and the Story of Crab Shells

To probe what these chemosensory cues mean in practice, the team studied what octopuses sense on crabs. They found that the crabs’ surfaces host diverse microbial communities, and that the microbes themselves—in particular those associated with crabs as they decay—shape what the octopus detects. When the team coated fake plastic crabs with a specific microbial signal, the octopus showed a dramatic behavioral shift: it approached the fake crab but avoided it after detecting the microbial cue associated with decaying or foul prey. This pointed to a microbial signature—not the surface itself—that informs the octopus about the prey’s identity and quality, a subtle but powerful mode of environmental interpretation.

"the diversity in these different communities is actually what's informing the octopus about what it's exploring" - Dr. Nicholas Bellono

Where on the Body Are the Senses? The Beak and a Possible Delicious Signal

The researchers also explored another sensor territory: an area surrounding the octopus’s beak that resembles a lip. Early work suggests this region may detect “delicious” molecules, potentially guiding feeding choices by a different chemosensory pathway than the suckers. While the precise nature of these signals remains under study, the data imply a distributed sensing system across multiple sensory surfaces, each tuned to different ecological cues.

Mating, Arms, and Receptors: The Hectocotylus

Cephalopods have unique mating biology, and the male’s specialized arm, the hectocotylus, is used to transfer sperm packets to the female. The team found that the hectocotylus carries the same core sensory receptors found in other arms, with some enrichment for receptors that bind metabolites secreted by the female ovary. This suggests that the octopus’ chemosensory toolkit supports a broad range of behaviors beyond feeding—extending into mating and egg care—by detecting chemical cues that guide an animal’s actions in intimate and reproductive contexts.

"the male hectocotylus does have the same sensory receptors that we find in the other arms" - Dr. Nicholas Bellono

Vision, Color, and the Surprise of Cephalopod Senses

Even as arms play a central role in sensing, vision remains a dazzling facet of octopus biology. The octopus possesses a highly developed visual system, and researchers are actively investigating how they achieve color-like capabilities despite long-standing assumptions of color blindness. The optic-brain architecture is large, and color perception in these animals may involve more than the simple presence of multiple opsins. The takeaway is that cephalopod perception continues to surprise scientists: what looks like a fixed sensory rule often turns out to be a flexible, evolving system that biology still has much to reveal about.

"Vision is another puzzling aspect of cephalopod behavior" - Dr. Nicholas Bellono

Broader Cephalopod Wonder: Beyond Octopuses

Bellono’s lab studies a range of organisms, including photosynthetic sea slugs that harvest chloroplasts from algae and even keep them alive for extended periods to perform photosynthesis. These investigations underscore the broader theme: cephalopods and their relatives challenge our assumptions about sensing, intelligence, and the extraordinary diversity of life’s strategies for interaction with the environment. The researcher’s curiosity is matched by a commitment to letting biology guide inquiry, rather than fitting phenomena into preconceived theories.

"pretty much every time that we've went into studying these animals, we end up finding something unexpected and different than what we imagined" - Dr. Nicholas Bellono

Closing Thoughts and Ongoing Questions

As cephalopod week on Science Friday continues, the conversation leaves us with a sense that octopuses are more than “very smart animals” in the abstract; they are finely tuned, multi-sensory systems that blend chemical, tactile, and visual information to navigate, eat, mate, and care for offspring. The ongoing research promises to refine our understanding of how these creatures perceive the world and how their sensory biology integrates across arms, beak-associated surfaces, and even reproductive organs. The episode highlights the joy of scientific discovery: each answer opens new questions about the astonishing ways life senses and responds to its surroundings.