A pair of previously unknown sea spider species has been identified in the shallow waters of the Salish Sea, between Washington State and the Canadian province of British Columbia, giving scientists their first documented encounter with members of the group in that stretch of coastline in more than a century. The discovery was made by a research team based at the University of British Columbia.
The new species were collected between September 2023 and August 2024 in shallow water off the islands of Vancouver and Quadra, both of which sit in the Salish Sea just off the British Columbia coast. According to the researchers, each of the animals measures roughly a centimeter across — small enough that the find underscores just how much of the ocean's biological inventory remains unmapped.
Both animals belong to the sea spider family, a group of marine arthropods classified in the class *Pycnogonida*. Scientists have so far identified more than 1,300 species of sea spiders worldwide, and the two Canadian finds add to that tally.
Cormac Toler-Scott, the lead researcher on the UBC team that made the discovery, told NPR that some sea spiders are not merely similar in appearance to the spiders found on land but are genuinely related to them. Land spiders, of course, typically have eight legs, and the resemblance can be striking to an untrained eye. The sea-dwelling relatives, however, differ from their terrestrial counterparts in several important 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."
That lifestyle has consequences for how easily they can be found. Creatures that hug the sea floor and move slowly are not the sort of animals that announce their presence, and a decade-plus of sampling in a single bay or channel can still turn up something new. The researchers said these were the first sea spiders recorded from the area in over 100 years, a gap that speaks as much to the difficulty of surveying marine invertebrates as to any rarity of the animals themselves.
One of the two new species, *Callipallene pilosuspedes*, carries a suite of distinctive features. It has red eyes, a three-lipped mouth shaped like a triangle, and a curved spine that covers its legs. It also possesses a set of limbs that emerge from the underside of the body, known as ovigers, which the animal uses to groom itself and comb off dirt and debris from its body.
The other new species, *Tanystylum kiixin*, was photographed by Toler-Scott with round eggs held inside its legs — a striking image of a reproductive structure that looks, at first glance, nothing like the egg sacs of familiar garden spiders. Photographs of the new species by Cormac Toler-Scott, courtesy of the University of British Columbia, document these details in detail.
The naming of two species at once is itself notable. Taxonomists generally describe one new species at a time, and the arrival of a pair from a single collecting effort suggests the researchers were working through a productive series of samples rather than stumbling on a single oddity.
The timing of the collections, spanning September 2023 through August 2024, points to work conducted across a full seasonal cycle. Sampling that spans seasons is more likely to capture organisms that appear only during certain windows, and for bottom-crawling invertebrates, repeated visits to the same shallow sites are the standard approach for building an accurate picture of what lives there.
For the field of marine biology, the practical implication of the find is a reminder of how incomplete the baseline remains. A species can persist in shallow, accessible coastal water — within sight of populated shorelines — for more than a century without being formally described, simply because no one has examined the specimens in hand. Each new name added to the *Pycnogonida* roster widens the picture of biodiversity in waters that are heavily used for fishing, shipping and recreation.
The discovery also offers a practical reassurance for anyone uneasy about eight-legged newcomers. Unlike the spiders that wander into homes, these animals never left the ocean. They cannot travel across a living room floor, they move at a crawl, and they depend entirely on the water that sustains them.
What the two species signify more broadly is that the Salish Sea, like most coastal waters, remains under-documented at the species level. The UBC team's work suggests that continued sampling — and the careful comparison of specimens against existing collections — is likely to turn up additional novelties in waters that researchers have been visiting for decades.
For now, the two new species stand as the most tangible recent additions to the more than 1,300 known sea spiders: animals about the size of a centimeter, living on the sea floor, carrying their eggs within their legs, and found off the coast of British Columbia by a team that had to look closely enough to notice.
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