Facts: The By-the-Wind Sailor (Velella velella)

The by the wind sailor is a hydrazoan found in temperate and tropical oceans around the world. They are related to siphonophores like the Portuguese man-of-war. Like siphonophores, each individual by the wind sailor is not a single organism. They are colonial organisms consisting of many individual polyps situated under the float. The polyps of each sailor are either all male or all female. Polyps are divided into separate groups within the colony. Some polyps specialize in feeding and reproduction, while others protect the colony and provide structural support. By the wind sailors are part of the pleustin, a group of planktonic organisms that live at the water-air surface. They have a disc-like chitinous skeleton comprised of concentric circles of sealed air chambers that provide buoyancy to keep the colony afloat. The disc, called a nematophore, is oval with a sail. The sail drives the colony along with the wind. The sails are fixed diagonally, either to the right or to the left. By the wind sailors are small and usually only between 2 and 3 inches in diameter. They tend to aggregate in large swarms. Their populations are typically larger in years with warmer winters. They have no independent form of movement and drift at the whim of the wind. They typically float far offshore, but during periods of sustained onshore winds, huge groups of these creatures can end up stranded along coastlines, including the US west coast. This is especially common during spring and early summer. After time in the sun, they dry out and lose their pigmentation. By the wind sailors have symbiotic algae called zooxanthellae in their tissues that provide them with nutrients. They also feed on zooplankton. The polyps catch their planktonic food with tentacles. These polyps are called dactylozoids. The tentacles contain stinging cells that are used to capture prey. The venom is considered harmless to humans, but some people may react more strongly to the venom than others. Nudibranchs like the blue sea dragon prey on by the wind sailors and then concentrate the stinging cells in their own tissues and use them for defense. They are also preyed on by organisms like planktonic sea snails, loggerhead sea turtles, and sunfish. Reproduction is performed by tiny medusae that bud free from gonazoids. The reproductive polyps. Medusae have many yellow patches revealing the presence of their symbiotic zooxanthellae. The tiny medusae sink as far as 6600 ft deep and produce larvae. The developing larvae float and rise back to the surface as they take on their adult forms. For more marine facts, click the SUBSCRIBE button!!