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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.
The mating of acorn barnacles is described as pseudocopulation. [25] [29] The goose barnacle Pollicipes polymerus can alternatively reproduce by spermcasting, in which the male barnacle releases his sperm into the water, to be taken up by females. Isolated individuals always made use of spermcasting and sperm capture, as did a quarter of ...
The growth rate then slows over the winter so that the year old barnacle averages 8 mm (0.31 in). Thereafter it grows at 5–10 mm (0.20–0.39 in) a year and the largest specimens, 30–40 mm (1.2–1.6 in) across are probably four to six years old.
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]
A. amphitrite and Balanus eburneus (ivory acorn barnacles), Cayo Costa State Park, Florida. Amphibalanus amphitrite is a species of acorn barnacle in the Balanidae family. Its common names include the striped barnacle, the purple acorn barnacle and Amphitrite's rock barnacle. It is found in warm and temperate waters worldwide.
Semibalanus balanoides (common barnacle, common rock barnacle, or northern rock barnacle) is a common and widespread boreo-arctic species of acorn barnacle. It is common on rocks and other substrates in the intertidal zone of north-western Europe and both coasts of North America .
The titan acorn barnacle is a large species with calcareous plates forming a steep-sided cone which grows to a height and width of 5 centimetres (2.0 in). [2] The plates are smooth and are fused together. They are pink and are separated by narrow purple or white radii and the aperture at the top is small.