Blue Jellyfish washed ashore

Billions of small, blue jellyfish-like creatures called “by-the-wind sailors” have washed ashore on the West Coast.

Images credit NOAA

These creatures, Velella velella (scientific name), which ride wind and currents, were washed up on the West Coast of the U.S, creating a dark blue carpet on the beach.

Professor of Biology at Monterey Peninsula College, Kevin Raskoff, told

‘The numbers, if you extrapolate, are awe inspiring. With some of my students we counted more than a thousand per meter. The numbers get astronomical pretty fast.’

Velella is a cosmopolitan genus of free-floating hydrozoans that live on the surface of the open ocean. Only one known species, Velella velella, is in the genus. Velella velella is commonly known by the names sea raft, by-the-wind sailor, purple sail, little sail, or simply Velella.

These small cnidarians are part of a specialised ocean surface community that includes the better-known cnidarian siphonophore, the Portuguese man o’ war. Specialized predatory gastropod mollusks prey on these cnidarians. Such predators include nudibranchs (sea slugs) in the genus Glaucus and purple snails in the genus Janthina.

Each apparent individual V. velella is in fact a hydroid colony, and most are less than about 7 cm long. They are usually deep blue in colour, but their most obvious feature is a small, stiff sail that catches the wind and propels them over the surface of the sea. Under certain wind conditions, they may be stranded by the thousands on beaches.

Blue Jellyfish Velella velellaImage credit wikimedia