A pair of sea spider species that had never been described by science has been identified in the shallow waters of the Salish Sea, the stretch of ocean and coastal channel between Washington state and the Canadian province of British Columbia. Researchers say the animals are the first sea spiders recorded from that area in more than 100 years.
The team, led by Cormac Toler-Scott of the University of British Columbia, gathered the animals between September 2023 and August 2024, sampling in waters off two British Columbia islands, Vancouver Island and Quadra Island. The specimens collected are small — roughly a centimeter across — but the significance of the find is measured in something other than size.
Both animals belong to the sea spider family, a group of marine arthropods assigned to the scientific class Pycnogonida. Researchers have named more than 1,300 sea spider species to date, and adding two more to that list is a reminder of how incomplete the catalog of ocean life remains. Much of what lives below the surface has never been seen, let alone formally described.
One of the pair is a new species given the name *Tanystylum kiixin*. Photographs released with the research, credited to Toler-Scott and the University of British Columbia, show one of the animals with round eggs held inside its legs — a reproductive arrangement characteristic of the group, in which egg masses are carried externally rather than deposited in a nest or laid in a sheltered spot.
The second species, *Callipallene pilosuspedes*, is described as a red-eyed animal with a three-lipped mouth shaped like a triangle and a curved spine that covers its legs. Among its more striking features are the ovigers, leglike appendages that grow from the underside of the body and that the spider uses to groom itself and to comb dirt and debris from its limbs.
Those traits — eight legs, a body plan that reads at a glance as a spider — are familiar enough to be misleading, and Toler-Scott said the resemblance to the spiders people watch cross floors and webs reflects a genuine relationship. The marine animals are, in fact, related to land spiders. What separates them, however, is a transition the sea spider lineage never made.
"They never made that transition to land," Toler-Scott said. "They really need to be in the water." Because the group stayed in the ocean, its members are built for submerged life rather than for the speed and exposure of terrestrial environments. They are slow, he said, and they tend simply to crawl across the seafloor rather than darting or climbing.
That dependence on water shapes where discoveries like this one happen. Sea spiders are bottom-dwellers tied to submerged habitat, so they turn up in shallow coastal water that researchers can reach and search without deep-sea equipment. Working off Vancouver and Quadra islands placed the team in habitat where such animals are plausible, and a 12-month window of sampling produced specimens that turned out to be unknown to science.
The more striking number in the research, though, is the century. Reporting that the species are the first sea spiders found in the area in more than 100 years is really a statement about the state of knowledge, not about the animals themselves. It suggests how rarely, or how unsuccessfully, the waters of the Salish Sea have been surveyed for this particular group.
A gap of that length does not mean the animals were missing from those waters. It means no one documented them. The Salish Sea is a heavily traveled corridor — shipping lanes, fishing grounds, urban shorelines — and it is not a place where marine biodiversity has been exhaustively inventoried, particularly for small, inconspicuous invertebrates that live on the seafloor.
Describing a species is slow, careful taxonomic work, and each accepted name becomes a permanent entry in the scientific record. Two new names in a family of more than 1,300 may appear modest on their own, but they mark mapped territory in a group whose family tree is still being drawn.
For Toler-Scott and his colleagues, the practical value of the find is likely to be found in the survey work that follows. An area that turns out to host undescribed animals is, by definition, an area with more to find — and the two new sea spiders offer a benchmark for comparing future sampling along the same coast.
The differences that separate the animals from their known relatives are fine details: the curve of a spine, the color of an eye, the geometry of a mouth, the placement of a tuft or a spine. Those are precisely the characters taxonomists rely on, and they are why images like the ones released with this work matter as much as the collections themselves.
The larger point is about attention as much as biology. Between Washington state and British Columbia lies a busy, developed body of water, and two species that no one had ever described were still there in it, about a centimeter across, crawling slowly over the seafloor.
For now the two new sea spiders are catalogued, photographed and named — and the same shallow coastal waters, researchers know from the century-long gap, are as likely a place as anywhere to turn up the next one.
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