Octopuses Pick Up On Invisible Microbial Cues to Avoid Rotting Food

How does an octopus use its arms? That’s the question a team of researchers set out to investigate. In the process, they discovered something intriguing — octopuses use receptors in their arms to pick up and interpret microbial signals in their environment and respond accordingly. The research was published in the journal Cell.

“Our results suggest that octopuses have tuned their sensory system to detect microbial signals,” lead author Rebecka Sepela, a postdoctoral fellow at Harvard University’s Department of Molecular and Cellular Biology, told Discover. “By doing so, they tap into a rapidly updating chemical language that informs them about both living and nonliving surfaces they touch.”

Sepela and her fellow researchers believe this is not a one-off discovery but instead reflects an ongoing interaction between animals — including humans — and the microbes that surround us.

How Octopuses Respond to Microbial Cues

In earlier research, a team at the Bellano Lab identified receptors in octopuses’ arms that allow the cephalopod to detect chemical changes in their surroundings — a process described as taste-by-touch.

Using these sensors, the octopus determines what is safe to eat and what is best to discard, a particularly useful skill in the dark seafloor crevices where these animals typically forage. The receptors are also thought to play a key role in brooding, enabling octopus mothers to discard unviable eggs.

These findings provided an important insight into the molecular mechanisms at play, but “we still did not know which specific molecules are detected in the ecological environment, and where these molecules come from,” Hao Jiang, a postdoctoral scholar at the University of California, San Diego’s Department of Neurobiology, who was involved in the research, explained to Discover.

Read More: Do Octopuses Dream? Their Colorful, Skin-Changing Sleep Cycles May Hold the Answer

Finding Out Which Molecules Prompt a Reaction

The next task was to find out which chemicals activate the octopuses’ receptors. This threw up two challenges.

“First, chemical space of the natural world is vast, guessing which molecules activate these receptors would be nearly impossible,” said Sepela. “Second, in the ocean, soluble chemicals are quickly diluted by turbulent seawater. So we needed a mechanism that would allow surfaces to retain stable chemical signatures.”

The researchers began by examining two surfaces that triggered important behavioral responses — crab shells and egg casings. The team found that decaying crab shells and rejected eggs were coated in microbial communities that separated them from their healthier counterparts.

To find out which specific chemicals are responsible, Sepela tested 295 strains of bacteria. Each strain was isolated and cultivated before it was put before the octopus’s receptors. Certain chemicals, including harmane-3-carboxylic acid (H3C) found on crab shells and lumichrome (LUM) found on rejected egg casings, prompted a reaction.

Later, when a fake crab covered in H3C was presented to an octopus, it was rejected — unlike the controls, which were treated like real crabs. Similarly, fake eggs dosed with LUM were discarded from the octopus’ den faster than controls.

This shows “the critical role of microbiomes in shaping animal sensory systems and ecological interactions,” said Hao to Discover.

Microbes and the Wider Animal Kingdom

These findings may have implications that extend to the wider animal kingdom.

“Animal evolution unfolded in a microbial world, and animals have had to sense, survive, and thrive within microbial chemical environments for their entire existence,” said Sepela, pointing to growing evidence that microbes influence behavior and physiology, from immunity to decision-making. “Microbes are not just passengers in the environment, they actively shape the chemical signals that animals use to make decisions about where to move, what to touch, and how to behave.”

This invisible interaction between animals and microbes may extend far into our evolutionary past — choanoflagellates, animals’ closest living relatives, respond to microbial signals by merging to form multicellular colonies.

Next, the team hopes to explore how other animals respond to microbial cues. “Much more work remains to be done,” says Sepela to Discover.

Read More: Rare Footage Reveals the Mysterious Seven-Arm Octopus Eating Its Prey

Article Sources

Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:

• This article references information from a study published in Cell: Environmental microbiomes drive chemotactile sensation in octopus
• This article references information from a study published in Nature: Structural basis of sensory receptor evolution in octopus