Creature Feature: By-the-Wind Sailors

December, 2014




Velella velella

This summer, North Coast beachcombers marveled in the miraculous, gelatinous presence of the Velella velella. These creatures washed up en masse beginning in mid-July, with sightings covering the entire western coastline from Washington state to southern California.
Velella velella—also known as by-the-wind sailors, purple sails, blue sails, litte sails, or sea rafts—are members of the phylum Cnidaria, which also includes jellyfish and coral. Somewhat similar to a jellyfish, these animals are bizarrely beautiful in appearance. The velella’s body is a brilliant translucent blue “float” with tiny tentacles dangling below. The ovular form is crossed diagonally by an erect, triangular sail.

Velellas still in contact with water maintain a plump and blue shape up to four inches in length, while those that have been washed above the reach of the waves transform into a desiccated plastic-like disc. Dried velellas so much resemble trashed cellophane that they were picked up by several volunteers on a recent beach cleanup!

The velella is described as a pelagic colonial hydroid. In other words, these animals inhabit the surface of the open ocean linked together in enormous colonies of individual “polyps.” They feed primarily on plankton and small fish as they float along, stunning the creatures with their short tentacles before funneling them into a centrally-located mouth. Velellas born in the northeast Pacific Ocean drift northwest to southeast per the angle of their sail. Conversely, specimens found in the western Pacific Ocean have sails angled northeast to southwest, and thus move in that direction as they catch the wind. In the southern hemisphere, the direction of the sails are reversed.

Many experts contend that this year’s mass strandings are probably not out-of-the ordinary, citing similar occurrences in years past. Others speculate that changes in climate, ocean chemistry, and ecology may be driving extreme “blooms” of velellas along with jellyfish. Fertilizer runoff into the marine environment leads to exploding populations of algae—the primary food source for velellas and jellies. Additionally, select fish species that would normally prey upon Cnidaria have been over-harvested throughout much of the velella’s range. These factors in combination with warming seas and more variable weather patterns could be blowing velellas higher north and further ashore in increasing numbers.

Whatever the nature of their appearance, the stranded Velella velellas offer a rarely seen glimpse into the vast unknowns of the open ocean. If observed, poked, and prodded in the wild, please wash your hands thoroughly before touching the eyes or face. These mysterious cobalt creatures are not thought to possess a sting powerful enough to pierce humans, but residual toxins could potentially irritate those with sensitive skin.