November 29th, 2009
Six species of barnacle were found in a week of sightings at Chesil. The six species included; the buoy barnacle Dosima faciculalaria, Scalpellum scalpellum and four species of goose barnacle; Lepas anserifera, Lepas hilli, Lepas pectinata and Lepas anatifera.
Dosima fascicularis is also known as the buoy barnacle. Young forms of the buoy barnacle settle on small floating objects in the water such as twigs or feathers, often in groups of about 2-5 juveniles. As they grow, attached to these objects, they produce a white, spongy secretion from cement glands that acts as a float and is similar in texture to polystyrene. Other barnacles can attach to this float and the colony increases in size. Dosima fascicularis is a pedunculate barnacle (has a stalk) which can be pale yellow to purple-brown in colour. Its capitulum can grow up to 30 mm in length.
Another stalked barnacle, Scalpellum scalpellum, attaches to rocks, hydroids, bryozoans etc. It has a flexible muscular peduncle that has an armour of calcareous scales. Its capitulum grows to about 30 mm in height and is usually a white-grey colour with thirteen plates. This is the only shallow water scalpellid barnacle in British waters.
Lepas anatifera is a common goose barnacle. It attaches itself to large floating objects and consists of two parts; the capitulum and the peduncle. The capitulum is about 50mm in length and contains the feeding tentacles and the body of the barnacle. It is oblong in shape and consists of five white plates separated by red-brown or black tissue. The peduncle is a flexible stalk that can grow from 4 up to 85 cm in length! It attaches the barnacle to floating objects.
Lepas pectinata is a small barnacle with a capitulum of only 15 mm. The outer surface or scutum of the barnacle is ridged and it attaches to both small and large objects, such as seaweed. Lepas anserifera is a rare species that is similar to Lepas pectinata but larger with a capitulum up to 40mm long. The barnacle, Lepas hilli is also a rarer species, similar to Lepas anatifera and is distinguished by a paler band between the peduncle and the capitulum.
All photos: Steve Trewhella
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Added by Rachelle Long