Deep-Sea Spiders Farm Methane-Eating Bacteria on Their Bodies todayheadline

Scientists have uncovered a peculiar feeding strategy among sea spiders living near underwater methane seeps: they cultivate bacteria on their own exoskeletons and then harvest them for food.

This discovery, published in the Proceedings of the National Academy of Sciences, reveals how these eight-legged creatures have adapted to thrive in one of Earth’s most chemically extreme environments.

Three new species of sea spiders from the genus Sericosura were found across methane seeps from California to Alaska, each hosting diverse communities of methane and methanol-consuming bacteria on their external surfaces. The spiders showed tissue carbon isotope values averaging -45‰, providing clear evidence of methane assimilation into their bodies.

Bacterial Buffet on the Exoskeleton

Using advanced microscopy techniques, researchers observed that the bacteria formed “uniformly spaced, volcano-like aggregations” across the spider bodies, surrounded by a protective layer of biological polymers. Many of these bacterial clusters appeared disrupted, with cellular footprints left behind—suggesting active grazing by the spiders.

“We propose that these sea spiders farm and feed on methanotrophic and methylotrophic bacteria,” the research team stated in their study. The arrangement resembles underwater agriculture, where the spiders maintain bacterial crops on their own bodies before consuming them.

What makes this relationship particularly remarkable is the diversity of bacterial partners involved. The spiders host three different families of microbes simultaneously: Methylomonadaceae, Methylophagaceae, and Methylophilaceae. No other animal species has been documented supporting this trio of methane-processing bacteria.

Generational Bacterial Inheritance

The research revealed an unexpected twist in reproduction. Male sea spiders carry egg sacs that contain identical bacterial communities to those found on adult surfaces, suggesting these microbial partners are passed from parents to offspring. This vertical transmission could explain how the spiders maintain their bacterial farms across generations.

During the study, researchers found that 50% of collected specimens were brooding males—significantly higher than typical for this spider family. The abundance of readily available bacterial food may fuel this enhanced reproductive success.

Methane to Spider Tissue in Five Days

To confirm the relationship, scientists conducted feeding experiments using carbon-13 labeled methane and methanol. Within five days, carbon from both compounds appeared in spider digestive tissues, proving that methane-derived nutrients were actively incorporated into the animals’ bodies.

The bacterial communities showed even faster uptake, with some cells reaching 12 times natural carbon-13 abundance. Even the sticky polymer matrix surrounding the bacteria became enriched with labeled carbon, suggesting the microbes share resources among themselves.

A Hidden Ecosystem Connection

This discovery expands our understanding of how methane—often considered merely a greenhouse gas—serves as a foundation for deep-sea food webs. The spiders join a select group of animals that harness methane as an energy source, though their farming approach appears unique.

Perhaps most intriguingly, the research uncovered evidence of metabolic cooperation within the bacterial community itself. The Methylomonadaceae bacteria produce methanol as they consume methane, which then feeds the other bacterial families in a cascading energy transfer that maximizes the spiders’ nutritional options.

The findings highlight how much remains unknown about deep-sea ecosystems. These spider-bacteria partnerships were discovered at the Del Mar methane seep, a relatively small seafloor area of just 625 square meters in well-studied waters off Southern California—yet they harbor completely novel biological relationships.

As lead author Bianca Dal Bó noted: “This work helps us better understand the biodiversity on our planet, which is crucial.” The research demonstrates that even in Earth’s most remote environments, life finds innovative ways to thrive through unexpected partnerships.

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