The study led by postdoctoral fellow Rebecka Sepela introduces a new paradigm: animal behavior can be directly shaped by microbial communities in the environment. By integrating sensory biology microbiology molecular evolution and structural biology the research demonstrates how octopuses process chemical signals from environmental microbes to guide behaviors such as hunting and caring for their young.

What Rebecka discovered is how microbes help octopuses determine which prey surfaces are worth pursuing and which egg surfaces deserve nurturing Bellono explains.

Octopuses are famously inquisitive using their arms to explore the seafloor in search of food and shelter. Previous work from the Bellono lab identified a family of sensory receptors in octopus arms that enable them to taste by touch.These receptors are especially attuned to detecting poorly soluble molecules chemicals that linger near surfaces rather than dispersing in water.

We began with the question: What are octopuses actually sensing in their environment? says Bellono. These receptors seemed perfectly suited to detect cues from the surfaces they investigate.

What Sepela uncovered was unexpected: it wasn’t the surfaces themselves that mattered but the microbiomes growing on them. In other words octopuses are detecting the microbes that colonize prey or eggs not the objects directly.

We wanted to understand how microbial signals are communicated to the octopus sensory system explains Sepela. Since these receptors sit right at the interface between the environment and the nervous system we asked which microbes might be capable of activating them.

To answer that question Sepela conducted an ambitious screening effort. She cultured nearly 300 microbial strains from the octopus’s natural environment and tested their ability to activate the octopus’s sensory receptors.

The idea was if a microbial strain could trigger a receptor it could send a neural signal to the octopus saying: This is something worth noticing Sepela explains.

The results were striking. Only certain microbes activated the receptors specifically those enriched on decaying prey or unhealthy eggs exactly the types of surfaces an octopus needs to identify quickly.

We then asked: What are these microbes producing that enables them to signal the octopus? says Sepela. Microbes act as chemical factories constantly responding to their environment by generating molecules that reflect those conditions.

This concept may be rooted deep in evolutionary history. Sepela points out that choanoflagellates the closest known relatives of animals shift from single-celled to multicellular forms in response to microbial signals implying that microbial communication could have influenced animal evolution from its earliest origins.

Source: https://www.mcb.harvard.edu/department/news/octopuses-use-microbial-signals-to-guide-complex-behaviors/