As It Happens

Rare deep-sea video captures 'carnivorous ravioli' starfish chowing down

After three weeks at sea, a deepwater research team is celebrating rare live sightings of a variety of starfish species — including one that looks remarkably like ravioli.

Inflatable gills give the starfish 'the look of a plump pasta,' says researcher Christoper Mah

A still from underwater video shows a group of ravioli starfish feeding on a sea sponge — with an urchin standing by, ready to snap up any leftovers. (NOAA Office of Ocean Exploration and Research/Windows to the Deep 2019)
Listen5:32

Transcript

At first glance, it looks like a handful of ravioli noodles propped on top of a stale old donut.

But make no mistake, this rare deep-sea footage captures what scientists are calling a "feeding frenzy," in which several starfish and a lone sea urchin join forces to slowly suck the life out of an unsuspecting sea sponge. 

And it's just one of the many marvels caught on camera by the crew of the National Oceanic and Atmospheric Administration's Okeanos Explorer as they study coral and other marine habitats off the southeast coast of the United States.

"It would I think surprise a lot of people that sea stars are capable of this almost brutal kind of attack," Christopher Mah, starfish expert at the Smithsonian Institution, told As It Happens guest host Robyn Bresnahan.

"It seems like that to other people. But, of course, to biologists it's simply part of ecology, of life."

This rare deep-sea footage from the U.S. National Oceanic and Atmospheric Administration shows ravioli starfish and a sea urchin feeding on a sea sponge. 1:05

The ravioli-shaped starfish in the video are officially known as the Plinthaster dentatus. The species dates back to the time of the dinosaurs, Mah says, but have only recently been seen alive. 

The deep-sea creatures earned their nickname because of their pentagonal shape and puffy swollen gills.

They are also sometimes referred to as "cookie stars" thanks to the flattened cookie cutter shape they take when deflated and on display in museums.  

"When they're seen alive like this, there's water that fills the body in order for it to breathe and so it's that really strong swollen, inflated look, which gives it the look of a plump pasta," he said. 

Plinthaster dentatus — the pasta of the sea — has been dubbed the "'ravioli' starfish because of its inflatable gills. (NOAA Office of Ocean Exploration and Research/Windows to the Deep 2019)

But there's more to a ravioli starfish than its looks.

The group feeding in the video shows that the marine creatures have "the same level of complexity as Savannah mammals," Mah said.

"We'd never seen them feeding, which in itself was novel — but the fact that they were in a group was amazing," he said.

"Seeing this attack, you think of them as living carnivorous raviolis attacking this sponge. And on top of it, we also have the sea urchin which has joined in on the fray."

He compared it to "watching some antelope being brought down by by lions ... followed by hyenas and many other kinds of predators."

Elusive, slimy and transparent 

NOAA also captured what it says is the first-ever footage of a living Sthenaster emmae starfish.

The elusive pale pink sea star was filmed munching on some coral, proving scientists' hypothesis it was a coral predator.

Researchers captured other species of starfish including this transparent sea star, likely in the genus Hymenaster. (NOAA Office of Ocean Exploration and Research)

They also photographed some Pteraster star fish, which are known as "slime stars" because they're covered in a thick, canopy-like membrane, as well as the Hymenaster, a completely transparent star fish whose gelatinous flesh exposes its stomach and internal skeleton.

On the left is a Pteraster, also known as a 'slime star' or a 'cushion star.' On the right is a Sthenaster emmae, pictured alive for the first time. (NOAA Office of Ocean Exploration and Research)

Mah says it's exciting to witness starfish living their lives in their natural habitat, and he hopes the footage will boost people's interest in these diverse and colourful creatures, which he says are a lot more interesting than people realize. 

While starfish may look like they're not doing much of anything, he says they actually exhibit complex behaviours — it's just hard for humans to appreciate because they move so slowly.

"There's a whole different world that people don't see because of the fact that these sea stars act in an almost separate timeframe," he said.

"Under a time lapse video, you can see a tremendous amount of complicated behaviour from sea stars, and we have yet to really understand what goes on in the species which live at great depth like this."

Written by Sheena Goodyear and John McGill. Produced by Chloe Shantz-Hilkes.

Comments

To encourage thoughtful and respectful conversations, first and last names will appear with each submission to CBC/Radio-Canada's online communities (except in children and youth-oriented communities). Pseudonyms will no longer be permitted.

By submitting a comment, you accept that CBC has the right to reproduce and publish that comment in whole or in part, in any manner CBC chooses. Please note that CBC does not endorse the opinions expressed in comments. Comments on this story are moderated according to our Submission Guidelines. Comments are welcome while open. We reserve the right to close comments at any time.