Hairy-legged red-eyed sea spiders discovered in the Salish Sea

If you’re swimming in the Salish Sea late at night and feel a skittering along your calves, tiny hairy feet tip-tapping their way higher and higher towards your face, don’t worry, it’s probably just the stuff of nightmares: hairy-legged, red-eyed sea spiders newly discovered by UBC researchers.

Two new sea spider species are the first described in the Salish Sea in almost a century. Their documentation and genetic analysis, published recently in Organisms Diversity & Evolution, helps fill a gap in a poorly understood group of animals.

“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,” said lead author Cormac Toler-Scott, who conducted the work as part of his master’s degree in zoology at UBC. “That's largely because people don't know much about what species exist here and what their lifestyle is.”

That’s the case for a lot of marine arthropods, Toler-Scott says. “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.”

Horrifyingly fascinating

Sea spiders evolved around 500 million years ago. Related to scorpions, spiders, and horseshoe crabs, they are arthropods that never left the ocean but look like their arachnid cousins except for their leg count which can get as high as 12, and a sucking proboscis. They range in size from less than a centimetre to more than 70 cm in Antarctica, hunting in the deeps for smaller things to eat – just to make you feel happier about all of this.

“They’ve retained some weird traits,” said Toler-Scott. “A lot of the shallow water species are quite small, and so they'll live as parasites on larger organisms, and they use this weird apparatus called a proboscis to suck the juices out of their host.”

Sea spiders breathe through their skin and the males rear the young. Females have ovaries spread throughout their limbs that produce eggs which then ‘pop out’ of a dedicated pore. During mating, the male will use limbs placed at the base of his head call ‘ovigers’ to scoop up the eggs, dab them in a glue secreted from his legs, and stick them to his own body in clusters of egg sacks for rearing.

Sarlacc pits and parasites on parasites

The new species were collected between September 2023 and August 2024 from dives up to 18 metres deep in a range of marine habitats and areas including Quadra Island, Vancouver, Bamfield, and Victoria.

In tribute to the long, curved spines covering its lower legs, one of the new species is named Callipallene pilosuspedes, a play on the Latin for ‘hairy feet’. It sports red eyes, a short proboscis with claws to grasp food before biting and a triangular, three-lipped mouth covered in sensory tendrils – a tiny marine Sarlacc pit, if you will.

It also possesses highly dexterous ovigers that can function as grooming tools. Under a microscope, researchers observed the animal wrapping the appendages around its legs and using attached comb-like spines to clean itself.

Before you decide to quit the ocean altogether, however, researchers found only one specimen of this species.

The second new species, Tanystylum kiixin, is named after the ancient Indigenous village site near where specimens were first collected. Pronounced ‘kee-hin’, the word comes from the sound of waves crashing at the base of the village site. Its egg-carrying limbs are much smaller and less dexterous, leaving the animal unable to groom itself effectively. Among the collected dirt and debris on the creature, researchers frequently found it covered with tiny parasites of its own, creating what Toler-Scott describes as "an ecosystem within an ecosystem within an ecosystem."

Officially awful

The research represents the first comprehensive study of sea spiders in the Salish Sea using both detailed imaging and DNA analysis. Along the way, the team generated genetic data for several species that had never been sequenced before and created an identification guide for sea spiders living in the region.

The two new species have been registered in a global database, but more wait to be found, says Toler-Scott. “I only had one field season but there's definitely more diversity out there that we haven't documented.”

So, never fear: more nightmare fuel awaits.

This research was funded by National Sciences and Engineering Research Council of Canada.

Interview language(s): English