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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.
Hemioniscus balani parasitically castrates adults of several species of barnacles, including Semibalanus balanoides, [2] Chthamalus fissus, Chthamalus dalli, and Balanus glandula. Rarely does more than one H. balani parasitize the same host, [ 3 ] but under conditions of heavy infestation, a single barnacle may contain as many as seven H ...
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]
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]
It is basically cone-shaped but can assume a more tubular shape in a crowded colony. Like other sessile barnacles, as an adult C. stellatus is a suspension feeder that stays in its fixed shell and uses its feathery, rhythmically beating appendages – actually modified legs – to draw plankton and detritus into its shell for consumption. [4]
Sacculina. Sacculina is a genus of barnacles that is a parasitic castrator of crabs.They belong to a group called Rhizocephala.The adults bear no resemblance to the barnacles that cover ships and piers; they are recognised as barnacles because their larval forms are like other members of the barnacle class Cirripedia.
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.