Two previously unknown species of sea spider have been discovered in the shallow waters of the Salish Sea, according to researchers at the University of British Columbia, in what appears to be the first documentation of these marine arthropods in the region in more than a hundred years. The finds were made between September 2023 and August 2024, in collections taken off the islands of Vancouver and Quadra in British Columbia, and both of the new animals measure only about a centimeter across.
The discoveries were made by a UBC team led by Cormac Toler-Scott, who discussed the finds with NPR. The Salish Sea is the body of water lying between Washington State and the Canadian province of British Columbia, an inland sea where currents mix fresh and salt water and where a rich variety of marine life thrives.
Despite the group's nickname, sea spiders are not the sort of arachnid that sends people reaching for a broom. They are marine arthropods belonging to the class *Pycnogonida*, a lineage distinct from the spiders, mites and ticks familiar on land. Scientists have so far identified more than 1,300 species of sea spiders, a number that researchers say continues to grow as scientists explore under-sampled coastal waters.
"What the sea spiders do have in common with their land relatives is the general body plan," Toler-Scott said. Some sea spiders resemble land spiders, bearing eight legs, and are in fact related to them. But the resemblance is where the comparison largely ends, because the marine animals never completed the evolutionary move onto land. "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 two newly described species is named *Callipallene pilosuspedes*. According to the researchers, 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 grow from its belly, known as ovigers, which the animal can use to groom itself and comb off dirt.
The second species, *Tanystylum kiixin*, was photographed by Toler-Scott of the University of British Columbia, and the resulting image shows one of the animals with round eggs visible inside its legs. That photograph offers a rare glimpse of a creature that is otherwise difficult to observe, since the animals move slowly across the seafloor and are small enough to be easy to overlook entirely.
For marine biologists, the most striking part of the finding may be less the anatomy of the new species than the location and timing of the discovery. Sea spiders are known from many parts of the world's oceans, but the Salish Sea had gone more than a century without a recorded new species from the group. The researchers' haul suggests that a habitat long considered comparatively well surveyed still holds obvious gaps.
A century-long gap can reflect real absence, but it can also reflect where people have looked. Sampling in coastal marine environments tends to cluster around accessible shorelines, harbors and popular research sites, leaving deeper shelves, offshore channels and seasonally difficult conditions undersampled. A pair of centimeter-long animals recovered in routine collections suggests that additional undescribed species may be waiting in similar water, waiting only for someone to sort through the samples.
The timing of the collecting also matters. The specimens were gathered across nearly a full year, from September 2023 through August 2024, which is consistent with animals that are present in the water year-round rather than brief seasonal visitors. The slow, crawling lifestyle Toler-Scott describes means these animals are not fast swimmers that might evade a net or a trap; they simply stay put on the bottom, filtering or grasping whatever the current brings them.
The naming of the new species follows long-standing conventions in marine taxonomy, in which discoveries are formally described, published and made available to the wider scientific community before being announced publicly. Giving a species a scientific name is what allows researchers elsewhere to compare notes, revisit the same animals in future surveys and fold the new data into broader studies of ocean biodiversity.
For the public, the practical upshot is reassuring. These animals are small, slow-moving inhabitants of saltwater, and the Salish Sea species in particular are not equipped for life on dry land, much less indoors. "They're quite slow moving. They just kind of crawl on the seafloor," Toler-Scott said — a description that puts the discovery squarely in the category of small wonders found by patient observation rather than looming threats.
The broader significance is cumulative. Each new species added to a group like sea spiders refines estimates of how much life exists in a given body of water, and those figures feed into conservation planning, habitat protection and decisions about which coastal areas are under pressure. The discovery that no new sea spider had been recorded in the Salish Sea for more than 100 years is a useful reminder that "well known" and "fully known" are not the same thing.
For now, the two new species remain a work in progress in the public imagination: a red-eyed animal with a triangular, three-lipped mouth and a curved spine over its legs, and a relative photographed carrying round eggs inside its legs. Both were collected in shallow water off Canada's British Columbia coast, both are about the size of a fingernail, and both are reminders that the census of ocean life is far from complete.
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