Thousands of little blue creatures are washing up on California beaches

The Velella velella, a name so nice you gotta say it twice.

Who are they? The tiny disc-like critters are colonial hydrozoans, classified under the phylum of cnidaria, and their eponymous genus of Velella (not a Game of Thrones reference).

• Formally titled the Velella velella (say that five times fast) you may know them as by-the-wind sailors.   
• The sailors are a couple of inches long, and vary in striking shades of cobalt and baby blue while they're alive.
• They have a similar build to jellyfish, but have a small sail protruding from their bell, explaining the name and their migratory patterns.

What's the big deal? California beachgoers have reported seeing thousands of the Velella velella along the shoreline recently, though they typically live far offshore.

• And their sails can explain it! They rely completely on the wind and ocean currents to move around, and when the conditions are just right, like with recent storms, they can get pushed up onto shore. 
• They also lose that beautiful blue hue once they leave the embrace of ocean waters and die onshore, typically becoming grayish or transparent. And with no exoskeleton to keep their shape propped up, they shrivel up to resemble plastic. 

• Their top predators include gloriously hued sea slugs and a special breed of predatory snail.  

Want more on oceans? Listen to the Consider This episode on why melting ice in Antarctica is a big problem for coastal Texas.

What are people saying? Marine biologist Julianne Kalman Passarelli is the education and collections curator at Cabrillo Marine Aquarium in San Pedro, California, and spoke with NPR about the mysterious blobby dudes.

On how they reproduce:

Hydrozoans are just really bizarre because they do something called alternation of generations. That's how they reproduce. And they go back and forth between a polyp stage, a colonial polyp stage, and a medusa stage. 

On the structure of the Velella velella and its ecosystem:

[The Velella velella is] a colony of animals. And if you look really closely, all those little things hanging down that look like tentacles are all different organisms within the same colony, and they all work together, kind of like coral, and they all have a different purpose. One is for reproduction, one is for feeding, and one is for defense. 

On the textures of the sail:

If you were to touch the top of the sail, it feels like plastic. It's quite thick. And actually what's in there is chitin. And that's the same material that is in the exoskeleton of crustaceans. So it's notoriously hard and protective, but you definitely don't want to pick them up and touch them because they are cnidarians. Their sting is not known to be as toxic as their relatives, the Portuguese man o' war, or even their more distant relatives jellyfish, sea nettles, things like that. But they can cause irritation. I wouldn't suggest picking them up with your bare hands. 

So, what now?

• As long as the conditions are right, the Velella velella will continue to wash ashore, until winds push them elsewhere. Real go-with-the-flow type guys.   
• Though it's not every year, seeing these tiny frisbees of the sea isn't the most unusual thing. "I've lived down here for over 20 years and I've seen them at least 10 times," Kalman Passarelli said. 

Learn more:

• Meet the worm blobs in the bowels of the Earth
• This floating ocean garbage is home to a surprising amount of life from the coasts
• California's destructively wet winter has a bright side. You'll want to see it

Copyright 2023 NPR. To see more, visit https://www.npr.org.