Two bizarre sea spiders discovered in Salish Sea after nearly 100-year gap

Cormac Toler-Scott was hunting for answers about how sea spiders respond to climate change when he realized he was looking for something that barely existed in the scientific record. The Salish Sea, that cold stretch of water between Vancouver and the Pacific Northwest coast, had not yielded a newly identified sea spider species in nearly a century. When Toler-Scott, a zoology master's student at the University of British Columbia, tried to find baseline information about these creatures, he found almost nothing. "I couldn't find anything," he said. "That's largely because people don't know much about what species exist here and what their lifestyle is."

That gap in knowledge matters because the Salish Sea's marine invertebrates face mounting pressure from climate change and human activity, yet scientists cannot protect what they cannot identify. To begin closing that blind spot, Toler-Scott and his colleagues spent a year—from September 2023 through August 2024—diving to depths of about 59 feet around Quadra Island, Vancouver, Bamfield, and Victoria, collecting sea spiders from the seafloor. The fieldwork paid off. They found two previously unknown species, the first new sea spiders described from the region since the 1920s. The findings appeared in the journal Organisms Diversity & Evolution.

Sea spiders belong to an ancient lineage of marine arthropods that diverged from their land-dwelling cousins around 500 million years ago. Unlike spiders and scorpions, they never left the ocean. Instead, they evolved into creatures that defy easy description: some carry as many as twelve legs, breathe directly through their skin, and feed through a tube-like appendage called a proboscis. The smallest species measure less than a centimeter; the largest, found in Antarctic waters, stretch beyond 28 inches. Many shallow-water species occupy the smaller end of that range, small enough to survive as parasites attached to larger organisms, using their proboscis to extract fluids from their hosts.

The first newly described species, named Callipallene pilosuspedes—Latin for "hairy feet"—looks like something from a fever dream. It has bright red eyes, long curved spines running down its lower legs, and at the front of its body, a short proboscis equipped with claws for grasping food, followed by a three-lipped mouth covered in sensory tendrils that resembles, as one researcher noted, a miniature Sarlacc pit from Star Wars. Only one specimen was collected during the study. Under the microscope, researchers discovered that C. pilosuspedes is fastidious about cleanliness. The animal possesses specialized limbs called ovigers, which males normally use to carry and tend eggs. In this species, those same limbs function as grooming tools: they curl around the spider's own legs while comb-like spines sweep across them, allowing the creature to maintain itself with remarkable precision.

The second species, Tanystylum kiixin, tells a different story. Named after an ancient Indigenous village site near where specimens were first collected—the word mimics the sound of waves crashing at the village's base—T. kiixin lacks the dexterous egg-carrying limbs of its hairy-footed relative. As a result, dirt and debris accumulate on its body. But the spider is not traveling alone. Researchers repeatedly found tiny parasites living on T. kiixin itself, creating what Toler-Scott described as "an ecosystem within an ecosystem within an ecosystem."

The fieldwork accomplished more than simply naming two new species. By combining detailed imaging with DNA analysis, the team conducted the first comprehensive study of Salish Sea sea spiders using both methods, generated genetic sequences for several species that had never been studied at the molecular level, and created an identification guide to help researchers recognize the animals living throughout the region. Both newly described species have been registered in a global database. Yet one field season was enough to suggest that the Salish Sea still harbors undocumented diversity. Toler-Scott acknowledged that more remains to be found, waiting in the cold water for the next researcher willing to dive deep enough to look.