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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 ...
The adult barnacle bears no resemblance to an acorn barnacle, but the larval development is typical of a barnacle, with four nauplius larval stages and one cyprid larval stage. [2] The female cyprid larva of L. panopaei has a spear-like stylet.
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]
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.
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]
While many barnacles deal with competition for space by organisms such as limpets and mussels by growing many organisms close together in colonies, Megabalanus responds by rapidly growing to a very large size. [4] Their large size also helps reduce predation, although it makes them large enough to be harvested for human consumption.
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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.