By Jake Buehler
Sea urchins are underwater lawnmowers, their unabating, vegetarian appetites capable of altering whole nearshore ecosystems. But the spiny invertebrates will also sink their teeth into something a bit more challenging — and dangerous — new research suggests.
In a first, researchers recently discovered urchins attacking and eating predatory sea stars. The observations flip a classic predator-prey script, researchers report in the June Ethology.
In 2018, marine behavioral ecologist Jeff Clements and his colleagues were at the Kristineberg Marine Research Station in Fiskebäckskil, Sweden, studying common sun stars (Crossaster papposus). At one point, Clements wanted to separate one of the sun stars for a short while and needed aquarium space. He placed the starfish in a tank containing about 80 green sea urchins (Strongylocentrotus droebachiensis).
“I thought, ‘Okay, there’s a bunch of sea urchins in there, these guys are predators of urchins, nothing’s gonna happen,’” recalls Clements, of Fisheries and Oceans Canada in Moncton. The urchins, he says, hadn’t eaten anything in two weeks.