......Velella velella :  By-the-wind Sailor



Velella velella :  By-the-wind Sailor

 


Millions of By-the-wind Sailors, or Velella velella, have been washing up on Sanctuary beaches this past week.


Velella velella up close and personal on Zmudowski State Beach.


On the surface, Velella velella can appear as an oil slick with their iridescent coloring.


Velella velella sailing on the surface.
 

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 anthomedusae.  
    The float and surrounding tissues are endowed with an attractive deep blue pigment.  The float contains a series of sealed air chambers that provide buoyancy.  Total width of the floating polyp is usually less than 6 cm.  Beneath the float is a grouping of several types of zooids, colored brown by the presence of zooxanthellae.   A large central mouth is surrounded by shorter reproductive stalks with mouth openings that bud tiny adult medusae that produce eggs and sperm.  Multitudes of tiny brownish medusae that never grow to more than 3 mm tall are cast off.  These then release the eggs and sperm that produce free-swimming larvae which develop into more floating polyps.  Dangling beneath the rim of the float are hollow tentacles that ensnare fish and invertebrate eggs, copepods and appendicularians.  Velella is found in warm and temperate seas throughout the world.  Although not dangerous to people, it's best not to touch your face or eyes if you've been handling beached individuals.  

 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.