Phylum Cnidaria / Class Hydrozoa / Order Anthomedusae / Family Velellidae
Springtime visitors to much of the coast of California have recently been mystified by
the appearance of long bluish rows consisting of jellyfish-like creatures that litter the
beaches. What you seeing are actually masses of thousands of unusual mobile
hydroids that normally travel at the surface with the aid of buoyant float tissue.
Propelled by winds that act on a somewhat rigid triangular sail held above the float,
Velella normally inhabit open ocean waters. The sail has a distinctive
cellophane-like texture. Wind patterns in spring and early summer may cast thousands
of these long-distance wayfarers onto beaches all along the West Coast. Individuals
with two types of sails that are mirror images of each other exist in a population - they
are thus pushed in opposite directions by the wind. Although previously classified
in the Order Chondrophora, recent considerations indicate an alliance with the
These small Hydrozoans normally float at the surface in offshore waters, but the recent southerly and westerly winds have brought them on to the beach. Because of their iridescent coloring, even to the trained eye they can appear as an oil slick when massed in large numbers on the surface of the water. Their "sail" is a triangular crest set diagonally across the top of the flat, oval base. They can "tack' in the manner of a sailboat. The bright blue By-the-wind Sailors do have stinging cells, but they are harmless to humans. They can grow to be 4 inches long, 3 inches wide, and 2 inches tall.