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These small cnidarians are part of a specialised ocean surface community that also includes the cnidarian siphonophore known as the Portuguese Man o' War, as well as some specialized predatory gastropod mollusks, including nudibranchs (sea slugs) in the genus Glaucus and purple snails in the genus Janthina, all of which eat Velella. Each Velella is a hydroid colony, and most are less than about 7 cm long. They are usually deep blue in colour, but their most obvious feature is a small stiff sail that catches the wind and propels them over the surface of the sea. Under certain wind conditions, they can become stranded on beaches in the thousands. In common with other Cnidaria, Velella are carnivorous animals. They catch their prey, generally plankton, by means of cnidocyst (also called nematocyst) -laden tentacles that hang down in the water. Though the toxins in their nematocysts are effective against their prey, Velella are harmless to humans, either because their nematocysts are unable to pierce our skin, or perhaps because humans do not react to the toxins encapsulated in their nematocysts. Nevertheless, it is probably wise not to touch your face or eyes if you have been handling Velella.
Bear Cut, Virginia Key, South Florida Peninsula