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What Are Velella Velella?

Each year, little blue creatures wash up along the California coast. They’re about two and a half inches across, blue, and shaped kind of like pringles. Sometimes they’re beached by the millions. They’re called velella velella.


“The marine life so nice they named it twice” are also commonly referred to as the “by-the-wind sailors,” because they travel along the ocean surface using their ridge, or sail, to catch the wind.


Joe Mueller is a professor of marine biology at the College of Marin, and an animal lover extraordinaire. He gets asked about velella velella a lot. Typically, beachings happen every three to seven years, and every time they wash ashore, Mueller’s inbox fills with questions.


Often, people assume that velella velella are jellyfish because they are jellylike with tentacles. They are wrong.


“They are not true jellyfish, they’re actually a colony of creatures we call hydroids,” says Mueller.


A hydroid colony is a cluster of polyps, which are sea anemone-like creatures. Together the polyps help operate a velella velella colony. Some specialize in stinging and some specialize in feeding.


The velella velella reproduce by asexually budding off pieces of the colony. The pieces that bud off are shaped like little bells and called medusa. They have both male and female parts.


“Somehow those parts find each other in the big wide ocean and they get together and make this little larvae [that] floats up to the surface and grows into this colony,” says Mueller.


For people, this would be similar to if your genitals fell off, went and found other genitals, had sex and made a baby without you. That’s how velella velella reproduce.


The velella valella feed on organisms that dwell along the ocean surface, including plankton and fish eggs. However, they don’t digest like most animals.


“They haven’t developed an anus yet,” says Mueller. “Food goes in and comes out the same place. It’s a cul-de-sac, not a one-way street.”  


The velella velella also have a mutually beneficial relationship with a special algae living on them. The algae feeds off velella waste and in return, the algae turn sunlight into sugars that feed the velella velella. So if a velella can’t eat for a long period of time, they can still survive.


The end of life for velella velella can be caused by the beach, or it can be brought on by one of its predators. These predators are beautiful in their own right and deserve a Google: They include a blue dragon nudibranch (Glaucus atlanticus), which is a type of sea slug and a purple snail, janthina janthina, which travels along the surface of the ocean using a bubble raft.



Credit Greg Schechter, Flickr Creative Commons

Why are velellavelella on the beach?


Beachings are a result of warm waters pushing the jelly-like creatures around. This is not in the velella velellas’ interest. When they come ashore, they all die.


“The best thing for [velella velella] is to stay out in the ocean. It likes to live beyond the continental shelf, ” says Mueller. “And to stay out there, it rides the Pacific Gyre.”


The Gyre is a clockwise current in the northern hemisphere,. The velella use their sails to tack in its circulating current. Mueller says if you look at velella from above, most sails are angled like a backslash on the oval bodies. This allows them to tack in the circular current forever.


In the southern hemisphere, winds go counterclockwise, so Mueller says velella sails flip below the equator and the backslash becomes a forward slash. This is where the trouble can start. “Their sail is designed for the Pacific Gyre,” he says “So southern is opposite of that and the sail doesn’t work, and they go the other way and they go onto land.”


Mueller says decades ago his mentor, a marine biologist named Al Molina, noticed that the velella velella beachings followed a pattern.


“He noticed over the many years, probably for him, 40-45 years, that he was observing these, that when they came ashore it was a sign of drought and when they didn’t it was a sign of a wet year.”


There haven’t been any scientific studies to confirm this; Mueller says it’s a difficult population to research because it would require floating research stations to follow velella valella around over several years. Until that’s feasible, we wait for them to come to us.

This piece originally aired on July 23, 2015.