Do you know which animals live on their heads and kick food into their mouths? The animals that live in this extraordinary position are the barnacles. You must have noticed barnacles encrusting large rocks at low tide on the shore and you might be forgiven for mistaking them for limpets or some other kind of mollusc.
In fact, they used to be called molluscs until it was noticed that the larvae hatching from the eggs has several features in common with crustaceans. The larva swims around for a while feeding and growing. It eventually changes into a shelled form and chooses a suitable place on a surface on which to settle head first.
A special secretion sticks it in position and it quickly encloses itself in a shell made up of plates. When the tide exposes the barnacle the plates stay closed to prevent loss of water from the animal. When the tide returns, however, the opt pair opens and the feathery feet are pushed out to comb the water for suspended food particles.
Where do barnacles live?
Barnacles will encrust practically any suitable surface on the shore. These include piles, pier supports, old tin cans and crabs which do not move fast enough to avoid the setting larvae. At one time they caused ships to slow done by settling on their bottoms but special paints are now used which inhibit the larvae from settling.
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