Little blue creatures have been spotted washing up in large numbers along Southern California’s coast over the past few weeks. But what are they? Where did they come from? Why are they washing up on our beaches?
Anya Stajner, a biological oceanography PhD student at UC San Diego’s Scripps Institution of Oceanography, said these creatures are a species known as Velella velella or “by-the-wind sailors.” Their common name refers to their sail-like appendage that sticks up above the water.
“Velellas float on the surface of the ocean and are passively moved across the water by the wind that catches their sails,” said Stajner, who studied these organisms as an undergraduate student. “Sometimes, when the wind is blowing towards the shore, large numbers of velellas get washed ashore like we’re seeing now.”
Although they may resemble jellies, they are not in the same group as true jellies. True jellies are part of a group called scyphozoans and Velella velella are part of a different group called hydrozoans. Velellas are more closely related to animals like the Portuguese man o’war. Velella do have stinging cells within their tentacles, but they are usually harmless to humans.
According to Scripps Pelagic Invertebrate Collection Manager Linsey Sala, Velella velella entered the scientific record in 1758. These creatures, which reach about three or four inches in diameter, are commonly seen off the coast of California and further north off Oregon and Washington.
"They have a pretty complex life history. There are additional stages where they will reside in the deep sea during the wintertime. Then, when conditions are such that they support a lot of zooplankton activity, like we see here in the spring, they transition to the stage with the sail, and they make an excursion from the deep sea up to the surface,” Sala said. "That's when we start to see them in their feeding stage, with their tentacles trailing underneath them just below the surface."
The movement patterns of velellas are unpredictable, but they are most likely to show up on Southern California beaches during late spring and early autumn as a result of local wind patterns and food availability.
To learn more about Velella velella, see below for our experts’ answers to some frequently asked questions.
About Scripps Oceanography
Scripps Institution of Oceanography at the University of California San Diego is one of the world’s most important centers for global earth science research and education. In its second century of discovery, Scripps scientists work to understand and protect the planet, and investigate our oceans, Earth, and atmosphere to find solutions to our greatest environmental challenges. Scripps offers unparalleled education and training for the next generation of scientific and environmental leaders through its undergraduate, master’s and doctoral programs. The institution also operates a fleet of four oceanographic research vessels, and is home to Birch Aquarium at Scripps, the public exploration center that welcomes 500,000 visitors each year.
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