University of British Columbia researchers describe two new sea spider species in the Salish Sea

The two species, each measuring about a centimeter across, were collected between September 2023 and August 2024 off Vancouver Island and Quadra Island in British Columbia. Cormac Toler-Scott, the lead researcher on the UBC team, told NPR that some sea spiders not only resemble spiders on land with eight legs but are also related to them, though the marine creatures differ from land spiders in several ways.

Sea spiders are marine arthropods in the class Pycnogonida, and scientists have described more than 1,300 species. "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, Callipallene pilosuspedes, has red eyes, a three-lipped mouth shaped like a triangle and a curved spine covering its legs. It also has limbs called ovigers that come from its belly and can be used to groom itself, combing off dirt and algae. "They're very clean and not all sea spiders can do this," Toler-Scott said.

The other species, Tanystylum kiixin, is named after an ancient Indigenous village near where it was found. Its shorter, stockier legs emerge from its chest and cannot be used for cleaning. Toler-Scott said the Tanystylum kiixin was covered in dirt and debris when he found it.

Sea spiders also reproduce differently from their land relatives: females develop the eggs, but males take over the job of caring for them until they hatch. The newly found species do not build webs. Both were found attached to a hydroid, a colonial marine animal that looks like a plant, and feed on it 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 said.

Sea spiders have no venom or fangs, and the newly discovered species rely mainly on camouflage to avoid being eaten. Many sea spiders, including these two, are transparent and take on the color of whatever they have eaten, he said.

Toler-Scott said finding new species is a goal for many researchers but remains uncommon. "It's everyone's kind of dream to find new species, but it's pretty uncommon," he said. "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 sea spider species in the future.