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Barnacle adults are sessile; most are suspension feeders with hard calcareous shells, but the Rhizocephala are specialized parasites of other crustaceans, with reduced bodies. Barnacles have existed since at least the mid-Carboniferous, some 325 million years ago. In folklore, barnacle geese were once held to emerge fully formed from goose ...
One barnacle may inseminate another up to eight times, and up to six concurrent penetrations may occur. The penis degenerates after copulation, and a new one is regrown the following year. [2] Up to 10,000 eggs may be produced, and they are stored in sacs within the shell cavity. [8] While the eggs are developing, the adult barnacle does not moult.
Balanus nubilus, commonly called the giant acorn barnacle, is the world's largest barnacle, reaching a diameter of 15 cm (6 in) and a height of up to 30 cm (12 in), [3] and containing the largest known muscle fibres. [4] [5] Balanus nubilus is a northeast Pacific species that ranges from southern Alaska to Baja California. [6]
Rhizocephala are derived barnacles that are parasitic castrators. Their hosts are mostly decapod crustaceans, but include Peracarida, mantis shrimps and thoracican barnacles. Their habitats range from the deep ocean to freshwater. [1] [2] Together with their sister groups Thoracica and Acrothoracica, they make up the subclass Cirripedia. [3]
Balanus trigonus, the triangle barnacle, is a species of barnacle in the family Balanidae.It is steep-sided, conical barnacle, has six shell plates and is pink in colour. Originally found only in the Indo-Pacific and the east Pacific coast, they have now been introduced to the Atlantic Ocean and are now found worldwid
This acorn barnacle is a moderate-sized one with a diameter of up to 22 mm (0.9 in). [1] The shell is formed by overlapping plates and has a calcareous basis. It has more the shape of a cylinder than the shape of a cone. The white operculum has heavily ridged walls. [1] It can live up to ten years. [1]
Acorn barnacle and acorn shell are vernacular names for certain types of stalkless barnacles, generally excluding stalked or gooseneck barnacles. As adults they are typically cone-shaped, symmetrical, and attached to rocks or other fixed objects in the ocean.
Balanus perforatus is a large barnacle which grows up to 30 millimetres (1.2 in) in both diameter and height. Its shape resembles a volcano with steep sloping sides. The six fused lateral calcareous plates are pale purplish-brown and often ridged vertically.