Bay Nature magazineApril-June 2016

The Ocean

The Purple Storm Snail, an Unusual Visitor to Northern California

April 1, 2016

The purple snail Janthina umbilicata, sometimes called the purple storm snail, is an unusual visitor to Northern California. Most of the time these marine snails drift on the surface of warm tropical seas, hanging upside-down from a raft of small bubbles. The snail makes its own raft one bubble at a time. By extending its foot to the surface and curving it into a concave shape, it creates an air pocket that is then pulled underwater, making a bubble. The snail coats the bubble with mucus and adds it to the raft.

This year, the brightly-colored snails seem to have drifted north following warm El Niño waters, then been blown ashore on North Coast beaches by strong storm winds. The snail pictured here was found alive in early March 2016 at Bodega Head by Bodega Marine Lab research coordinator Jackie Sones and BML marine biologist Eric Sanford, who brought it back to Sanford’s lab. Once in a lab tank, the snail created a new bubble raft, and then feasted on a gelatinous by-the-wind sailor (Velella velella) that the scientists offered it.

The purple storm snail is one of five species in the Janthina genus and was given its scientific name in 1840 by the French naturalist Alcide d’Orbigny, who collected it in Cuba. (Charles Darwin considered him a competitor, complaining in a letter to his Cambridge mentor, “I am very selfishly afraid he will get the cream of all the good things before me.”)

Since purple snails are such a rare occurrence on our coast, Sones and Sanford want to know where else they might have landed. You can upload photos and observations to the citizen science app iNaturalist—which has never had an observation of any species of Janthina north of San Diego—or visit Sones’s blog at

About the Author

Eric Simons is a former digital editor at Bay Nature. He is author of The Secret Lives of Sports Fans and Darwin Slept Here, and is coauthor, with Tessa Hill, of At Every Depth: Our Growing Knowledge of the Changing Oceans.