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3,000 Feet Beneath the Ocean, Scientists Found Spiders With a Hidden Superpower
Here's what you'll learn when you read this story:
In 2023, scientists from the Occidental College of Los Angeles collected 36 specimens of sea spider living near methane seeps along the Pacific Coast from California to Alaska.
Upon examining the arachnid-like creatures, they discovered that these deep sea species form a symbiotic relationship with methylotrophic bacteria, which provide a food source in the pitch dark aphotic zone.
This new study paints a more complete picture of how the deep sea helps keep methane (a potent greenhouse gas) from escaping into the atmosphere.
When you live in the ocean's aphotic zone, where absolute darkness reigns, you need some creative solutions to some pretty existential questions. Chief among them: what are you going to eat?
For a variety of ocean floor-dwelling species, including mussels, worms, and sponges, that answer lies with chemosynthetic bacteria—organisms that flourish around methane seeps where the gas escapes the Earth's crust. A new study shows that three species of the sea spider genus Sericosura also demonstrate a similar ability, which helps explain why these spindly-legged organisms are found in such abundance near methane seeps. The results of the study were published in the journal Proceedings of the National Academy of Sciences (PNAS).
Despite the name, sea spiders aren't actually spiders (though, that'll likely be of little comfort to an arachnophobe). Although they look remarkably similar, sea spiders have a thinner cephalothorax than their eight-legged land-based lookalikes, and their legs tend to have more joints. Oh, and they also live in the deep ocean—one of biology's true final frontiers of scientific inquiry. This hard-to-reach ecosystem is why many aspects of their lives remain a mystery.
'Our study aimed to examine the ways in which often overlooked animals might take advantage of novel energy sources, such as methane,' Shana Goffredi, the senior author of the study from the Occidental College of Los Angeles, said in a press statement. 'While the deep sea feels far away, all organisms are interconnected, and the processes in one ecosystem affect another.'
In 2023, Goffredi—along with two students, including Bianca Dal Bó—embarked on a two-week research expedition on the R/V Atlantis to study these creatures in their deep-sea habitats. With the help of a piloted submersible named Alvin, they examined and collected sea spider specimens located 1,000 meters (3,280 feet) below the ocean surface from the Del Mar and Palos Verdes seeps in California and the Sanak seep in Alaska. Of the 36 specimens recovered, three of the spiders represented entirely new species.
'I had seen animal samples in preservatives in the lab for so long, so it was beautiful to finally see them moving around in their natural habitat,' Dal Bó said in a press statement. 'It made me feel all the more connected to my project and these fascinating ecosystems.'
While performing experiments on board, Goffredi and Dal Bó incubated the sea spiders in seawater with methanol and a heavy isotope of methane. Because this isotope is rare in nature, the researchers could track its impact on the sea spiders, including if it was ingested. They found that methylotrophic bacteria located on the sea spiders' exoskeletons served as a source of a food.
'Evidence from tissue isotopic analysis, microbiome sequencing, and live-animal incubations followed by 13C-methane isotope probing confirms active incorporation of methane-derived carbon into spider tissues,' the authors wrote. 'This research highlights a previously unknown interaction between an animal lineage and chemically fueled microbes, introducing another symbiotic pathway for direct microbial transfer of methane carbon into animal biomass in the deep sea.'
This transfer of methane carbon into animal biomass is particularly important for scientists to understand, as methane is one of the most potent greenhouse gases. Sea spiders—with the help of other deep ocean-dwelling animals—are doing their part to keep these gases locked away in the ocean, so they don't reach the atmosphere and exacerbate the ongoing climate crisis.
'While the deep sea feels really far away, all organisms are interconnected,' Goffredi told CNN. 'Even though they're small, these animals have a big impact in that environment. We can't ever hope to sustainably (use) the oceans if we don't really understand the oceans.'
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