Researchers Discover Two New Sea Spider Species in Salish Sea After Century-Long Absence

Researchers in Canada have discovered two new species that are related to spiders, but you don't have to worry about them crawling across your living room.

The new species are part of the sea spider family and were found in shallow waters in the Salish Sea between Washington State and the Canadian province of British Columbia. These sea spiders are the first to be found in that area in more than 100 years, according to the researchers. The newly discovered species, which measure about a centimeter across, were collected between September 2023 and August 2024 off of the islands of Vancouver and Quadra in British Columbia.

Sea spiders are marine arthropods that are part of a class called Pycnogonida. Scientists have discovered more than 1,300 species of sea spiders.

Cormac Toler-Scott, lead researcher on the team at the University of British Columbia that discovered the new species, told NPR that some sea spiders not only resemble spiders on land with eight legs, but are also related to them. However, the marine creatures are different from land spiders in several ways.

"They never made that transition to land," Toler-Scott said. "They really need to be in the water. They're quite slow moving. They just kind of crawl on the seafloor."

One of the new species of sea spiders, called Callipallene pilosuspedes, has red eyes, a three-lipped mouth shaped like a triangle and a curved spine that covers its legs. It also has limbs that come from its belly called ovigers that can be used to groom itself and comb off dirt as well as algae. "They're very clean and not all sea spiders can do this," he said.

The other newly discovered species, Tanystylum kiixin, named after an ancient Indigenous village near where it was found, has shorter and stockier legs coming out of its chest. These can't be used to clean themselves. The Tanystylum kiixin was covered in dirt and debris when he found it, Toler-Scott said.

Sea spiders also reproduce differently than the ones that live on land. While the females develop the eggs, the males take over the responsibility for caring for them until they hatch.

And when it comes to food, sea spiders don't make a web and eat their dinner like a land spider. The newly found sea spiders were found attached to a hydroid, a marine animal that looks like a plant and lives in colonies. They feed on the hydroids like a parasite.

"They're both living on that and feeding on that, kind of walking through it like a maze, and they just kind of poke a hole into the hydroid itself, and then they suck the juices out of it, like the cells out of the hydroid. That's how they get their food," Toler-Scott explained.

Sea spiders don't have venom or fangs and the newly discovered species mainly rely on camouflage to avoid being eaten. Many sea spiders, including the newly discovered ones, are transparent and take on the color of whatever they have eaten, he said.

"It's everyone's kind of dream to find new species, but it's pretty uncommon," said Toler-Scott. "It's hard to get funding for this kind of work because you go into it not really knowing what you're going to get."

With additional dives planned, the British Columbia researchers expect to find more species of sea spiders in the future.