Scientists Describe Two New Sea Spider Species Found in the Salish Sea

Researchers at the University of British Columbia have described two new species of sea spider found in the Salish Sea, the first such discoveries in the inland waters between British Columbia and Washington state in nearly a century.

The species, detailed in a paper published this month in the journal Organisms Diversity & Evolution, were collected during scuba dives conducted between September 2023 and August 2024 at sites including Quadra Island, Bamfield and Victoria, at depths of up to 18 metres. Sea spiders, formally known as pycnogonids, are not true spiders but a distinct class of marine arthropod that has existed largely unchanged for hundreds of millions of years, with thin, hollow legs through which parts of their digestive and reproductive systems extend, since their bodies are too small to contain the organs entirely.

One of the new species, Callipallene pilosuspedes, is distinguished by long, curved spines covering its lower legs, along with red eyes and a triangular, three-lipped mouth equipped with claws. Its Latin name combines "pilosus," meaning hairy, with "pedes," for feet. According to the university's own account of the research, the species is capable of grooming itself using comb-like structures on its limbs, a trait not shared by the second new species described in the same paper.

That second species, Tanystylum kiixin, takes its name from an ancient Indigenous village site near where the specimens were first collected, a word pronounced "kee-hin" and drawn from the sound of waves striking the shoreline at the base of the village. Unlike its counterpart, Tanystylum kiixin has small, less dexterous egg-carrying limbs that leave it unable to clean itself effectively, and researchers frequently found the animal's body coated in debris and small parasites living on its surface.

Filling a taxonomic gap

The lead researcher on the project, Cormac Toler-Scott, an alumnus of UBC's zoology department, said identifying and classifying such organisms is a prerequisite for understanding broader threats facing marine ecosystems. "In order to understand how marine invertebrates are being impacted by things like climate change and how we can better protect these key elements of the ecosystem, we have to be able to identify them," Toler-Scott said, according to the university's release. Sea spiders as a group remain poorly studied relative to their ecological role, with roughly 1,300 described species worldwide despite their presence in oceans at nearly every depth, from tide pools to waters several kilometres deep.

The research was funded by Canada's Natural Sciences and Engineering Research Council, and the genetic analysis used to confirm the species' distinctiveness relied on DNA barcoding methods that have become standard for resolving ambiguous cases within understudied invertebrate groups. Both new species were compared against known pycnogonid specimens held in museum collections before researchers concluded neither had previously been documented anywhere in scientific literature.

The Salish Sea, an intricate network of straits, channels and inlets stretching from the southern tip of Puget Sound to the northern end of the Strait of Georgia, has been intensively studied by marine biologists for more than a century, making the discovery of previously undocumented species notable to specialists in the field. The last new sea spider species described from the same waters dates back nearly one hundred years, according to the research team, underscoring how much of the group's diversity had gone unrecorded even in a well-trafficked and comparatively well-studied body of water.

Toler-Scott and colleagues collected the specimens as part of broader survey work examining invertebrate biodiversity in nearshore habitats, work that researchers say has taken on new urgency as ocean temperatures shift and coastal development continues to alter habitats used by bottom-dwelling species. Because pycnogonids are highly specific to particular habitat conditions and often immobile for most of their adult lives, scientists consider them useful indicator species for tracking subtle changes in marine environments before those changes become apparent in better-studied, more mobile species.

The paper's authors say further surveys are planned in other underexplored sections of the Salish Sea, where they expect additional undescribed species remain to be found among the region's rocky reefs and kelp beds.