Morphology

The body of the Capitulum mitella barnacle often reaches 5 centimetres in total length and consists of a tough stalk (or peduncle) topped by a capitulum.

The capitulum consists of yellowish shell plates that surround and enclose the barnacle 'body'.

The peduncle is contractile and covered by numerous fine scales, while the fan-shaped capitulum has 8 shell plates with 18 to 25 small shell plates in a basal ring below.

Both peduncle and the tissues associated with the shell plates are strictly derived from the head of the barnacle which is an atypical crustacean.

The 'body' within the mantle cavity - the (strictly external) space bound by the shell valves - is attached to remaining tissue. It is made up of the rest of the head - the oral cone with mouthparts - and the thorax with six pairs of thoracic legs. The abdomen is vestigial.

Glossary
Hermaphrodite

An animal that has reproductive organs of both males and females of the species, and can act as ‘male’ or ‘female’ in the reproductive process.

Nauplius

First stage larvae of crustaceans.

Phytoplankton

Tiny water dwelling plants.

Lower eulittoral zone

An area of shoreline that ranges from the high water mark to areas that are permanently submerged.

Sessile

Permanently attached and not free to move.