(Vellela vellela), a subtropical cnidarian—a relative of jellyfish—that is neustonic (floats at the sea surface). Its body is oval, grows to a length of 8 centimetres (3 in.), contains a gas-filled float, and has a sail on top that sticks up into the air. The sail is set so that some individuals tack to the right and other to the left, so they tend to accumulate along slicks and windrows. On the underside there are numerous delicate tentacles armed with stinging cells that stun its prey of small plankton. Its blue coloration, typical of most neustonic animals, may either be camouflage, making the animals difficult to pick out against the blue of the ocean, or provide protection against the damaging effects of ultraviolet light. Vellela has its own predator, the purple sea snail (Ianthina). Seen from a boat, Ianthina looks like a cigarette end floating in the water because it secretes itself in a bubble float. Both are occasionally washed up on beaches in large numbers in Britain, usually in late summer after a period of south-westerly winds.
M. V. Angel
Subjects: Maritime History.