Acorn Barnacles are cone-shaped marine crustaceans that can be found along most of the rocky coasts of England at low tide. They can be seen clinging onto rocks and other hard surfaces such as on the underside of boats.

The Acorn Barnacle usually grows to a maximum of one and half centimetres and it has the name ‘Acorn’ because of its cone-shaped shell. The shell is usually an off-white colour and is made up of six plates which surround and protect the barnacle’s body. The Acorn Barnacle opens its shell when the tide is in and then extends six legs out of the shell. The legs are quite small and feathery and are used to filter water to help the Acorn Barnacle to find food particles. It closes the shell when the tide goes out to stop itself from drying out.

Acorn Barnacles are ‘hermaphrodite’ which means they are both male and female. They carry their eggs in special cavities within their shells for about five months. When the larvae hatch out of the eggs, they swim freely in the sea and become part of zooplankton until they grow bigger and can attach themselves to objects.