Newly Discovered Sea Spiders Feed on Methane-Bacteria, Offering Clues to Deep Ocean Ecosystems
A surprising deep-sea discovery is challenging long-held assumptions about life in the ocean’s most extreme environments.
Scientists have identified three new species of sea spiders that appear to gain nutrition in an unusual way—by consuming bacteria that live off methane gas seeping from the seafloor.
The findings, published in the Proceedings of the National Academy of Sciences, open up new questions about how marine
creatures adapt to harsh underwater conditions.
Life Where Sunlight Never Reaches
The deep ocean is a challenging place to survive—frigid temperatures, crushing pressure, and no access to sunlight make life here incredibly unique.
Yet these newly identified sea spiders, known as Sericosura, have found a way to thrive. Instead of hunting prey, they feed on
microorganisms that flourish in methane-rich sediments.
Methane naturally seeps from the ocean floor as organic matter breaks down, providing fuel for certain bacteria.
These bacteria, in turn, attach themselves to the surfaces of animals like Sericosura. The sea spiders then “graze” on these microbial
communities—much like livestock feeding off pasture.
Lead researcher Shana Goffredi, a marine biologist at Occidental College, described the process:
“The spider grazes its own body, eating the bacteria that live there, which convert methane into nutrients.”
A Symbiotic Relationship
This form of nutrient intake—through hosting and then feeding on bacteria—is highly unusual in sea spiders.
In contrast to other species that catch small prey with specialized mouthparts, Sericosura appears to rely entirely on its microbial
companions for food. The bacteria transform methane and oxygen into energy-rich compounds like sugars and fats, creating a sustainable food source.
This mutually beneficial system may also have broader environmental impacts. Since methane is a potent greenhouse gas,
the presence of bacteria that consume it at the ocean floor may help limit its release into the atmosphere.
“Even the smallest organisms can influence major Earth systems,” said Goffredi. “These sea spiders show how interconnected deep-sea life really is.”
Inheriting Microbiomes From Birth
Another intriguing aspect of the study is how the bacteria are passed on to future generations. Male Sericosura spiders carry egg sacs containing
hundreds of offspring. Once the larvae hatch, they are exposed to the same bacteria that coated the parent, suggesting a built-in way to
transfer this symbiotic relationship.
Stable isotope testing confirmed that the bacteria are not just passengers—they are a nutritional source consumed by the young spiders.
Dr. Nicole Dubilier of the Max Planck Institute emphasized the resilience of the relationship:
“Even when most of the bacteria are eaten, the rest can survive and continue reproducing. It’s a beautifully balanced system.”
Unlocking the Secrets of the Deep
This discovery adds to a growing body of research showing that deep-sea ecosystems are far more complex and diverse than once believed.
Goffredi notes that many marine species appear to be closely tied to specific locations on the seafloor, each adapted to distinct environmental conditions.
Rather than being a barren wasteland, the deep ocean is a mosaic of specialized life forms—some of which may help inform climate
models or even inspire new technologies.
As research continues, these methane-grazing sea spiders may help scientists better understand the ways in which life adapts, survives, and
shapes the world in one of Earth’s most mysterious habitats.
