Scientists Discover First Known Sea Spider Species That ‘Eat’ Methane With the Help of Bacteria
The research offers new insights on interactions between creatures on the mysterious seafloor and sheds light on the methane cycle
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Researchers have discovered three new sea spider species that are powered by methane deep beneath the ocean.
Shana Goffredi, a biologist at Occidental College and the study’s senior author, tells Erin Rode at SFGATE that the discovery was a “happy accident.” She and her colleagues were originally researching the ecosystems around methane seeps—deep-sea ecosystems where methane gas from the Earth’s crust escapes into the ocean.
The team collected different organisms and water samples from two sites off the coast of California and one from Alaska for further analysis. That’s when they noticed the deep-sea spiders they brought back had carbon isotopes derived from methane in their tissues.
Those unusual spiders, the team found, collect bacteria on their bodies, which, in turn, convert methane gas into nutrients the spiders can eat, like fats and sugars. “Just like you would eat eggs for breakfast, the sea spider grazes the surface of its body, and it munches all those bacteria for nutrition,” says Goffredi to Kameryn Griesser at CNN.
Even the bacteria benefit from this symbiotic arrangement—they get to live in a habitat with everything they need on the exoskeletons of the spiders. “Even if 80 percent of the population are eaten (by the spiders), it’s worth it for the 20 percent to keep surviving and reproducing,” says Nicole Dubilier, a researcher at the Max Planck Institute for Marine Microbiology who was not involved in the work, to CNN.
The findings were published in the journal Proceedings of the National Academy of Sciences on June 16.
This discovery marks the first time scientists have observed this behavior in sea spiders. Other sea spider species, like many spiders on land, will capture and pierce their prey to suck up their internal fluids. These spiders, however, appear to lack the necessary body parts to do so. Instead, they seemingly use their teeth or “lips” to gather and eat the bacteria, either off their own exoskeletons or those of other individuals.
Measuring around 0.4 inches long, the recently found species are tiny. But they hold big implications for further research: The team writes that these discoveries can help deepen our understanding of oceanic methane cycles. Methane might be converted into food for these sea spiders, but it’s also a greenhouse gas that contributes to climate change. By feeding on methane, sea spiders and other deep-sea creatures like sponges and tube worms might be keeping some of the gas from reaching the atmosphere.
“While the deep sea feels far away, all organisms are interconnected, and the processes in one ecosystem affect the other. The deep sea is so important. It’s involved in climate regulation, production of oxygen and supply of fisheries,” says Goffredi to SFGATE. “So, it’s really important to understand the biodiversity of these unique places.”
The study authors write that sea spiders at methane seeps are understudied, and it’s still unclear how they fit into the food webs of their environments. But because each of these species was found in a highly specific area far from the others, the team suggests that more exploration will likely unearth other methane-eating sea spider species.
“People tend to think of the deep sea as a kind of homogeneous ecosystem, but that’s actually untrue. There’s a lot of biodiversity by region, and animals are very localized to specific habitats on the seafloor,” Goffredi says to CNN. “You have to be very careful if you decide to use the seafloor for mining, for example. We don’t want to cause any kind of irreparable harm to very specific habitats that aren’t found anywhere else.”
