One field season in the Salish Sea turned up two sea spider species new to science

The gap Toler-Scott ran into is the ordinary kind. He wanted to know how sea spiders in the Salish Sea respond to warming water and human disturbance, and the literature had nothing to answer with. "I was interested in how sea spiders are impacted by climate change and human disturbance, because marine invertebrates in the Salish Sea are particularly at risk, and I couldn't find anything," he said ^[4]. He put that down to something more basic: "That's largely because people don't know much about what species exist here and what their lifestyle is" ^[6].

Sea spiders are arthropods that evolved around 500 million years ago and never left the ocean, related to spiders, scorpions and horseshoe crabs, with as many as 12 legs and a sucking proboscis ^[17]. They breathe through their skin, and the males rear the young ^[19]. "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 ^[5].

Callipallene pilosuspedes is known from one animal ^[10]. One specimen is enough to describe a species. Abundance, the amount of variation between individuals, and thermal tolerance all take more animals than that. The description does rest on direct observation: under a microscope, the animal wrapped its egg-carrying ovigers around its own legs and cleaned them with attached comb-like spines ^[9]. Its lower legs carry the long curved spines the Latin name refers to, and it has red eyes, a short proboscis with claws, and a triangular three-lipped mouth covered in sensory tendrils ^[8].

The other new species, Tanystylum kiixin, has much smaller, less dexterous ovigers and cannot clean itself effectively ^[12]. In the dirt and debris on those bodies the team repeatedly found parasites of the sea spider's own, which Toler-Scott described as "an ecosystem within an ecosystem within an ecosystem" ^[13]. It is named for the ancient Indigenous village site near where the first specimens came up, pronounced "kee-hin", a word that comes from the sound of waves breaking at the base of the site ^[11].

The sampling was one season, September 2023 to August 2024, about twelve months ^[7][21], on dives no deeper than 18 metres at Quadra Island, Vancouver, Bamfield and Victoria ^[7]. That is a shallow slice of habitat for a group whose known species run from under a centimetre to more than 70 cm in Antarctica, a range of more than seventyfold ^[18][22]. Nothing in the work measures a climate response. What it produced is a regional identification guide and genetic data for several species that had never been sequenced ^[14]. A monitoring program needs those inputs before it can detect anything.

The two species are now registered in a global database ^[15]. Toler-Scott expects the regional count to keep climbing: "I only had one field season, but there's definitely more diversity out there that we haven't documented," he said ^[16].