Velella velella, or by-the-wind sailor
Usually in spring, but occasionally in winter, great windrows of blue- to purple-bodied jellyfish line our beaches. The scientific name of the jellyfish is Velella velella. A good common name is “by-the-wind sailors,” or you might prefer the shorter “purple sailor.” Some beachcombers call them Portuguese man-of-war, but this is incorrect. The man-of-war jellyfish live only in warm waters.
Velella is an offshore resident. Winds blowing gently against its triangular, clear sail move the jellyfish. The sail is set diagonally to the long axis of the animal. On our side of the north Pacific Ocean, their sails are set in a northwest to southeast direction. In the southern hemisphere, sails are reversed. As long as the winds blow gently, Velella tack at about 45 ̊ away from the following wind. This keeps the animals offshore.
When winds are strong, Velella loses its tacking ability and begins spinning and more directly follow the wind. Strong westerly winds, then, are what drive these animals onto our beaches.
All jellyfish have stinging cells in their tentacles. Most people are not bothered by touching one from our beaches with their hands. However, you should not rub your eyes or put a finger in your mouth after handling a jellyfish because this could cause you pain—and maybe even more serious problems. Also, you should avoid walking barefoot through freshly beached jellyfish.
Velella is not the only jellyfish you might find on your beach walks.
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