Fossil range: Early Palæozoic - recent, although only common from Neogene
"Cirripedia" from Ernst Haeckel's Kunstformen der Natur (1904). The Paleozoic or Palaeozoic Era (from the Greek palaio (παλαιο "old" and zoe (ζωη "life" meaning "ancient life" The Neogene is a geologic period and system starting 2303 ± 0 Ernst Heinrich Philipp August Haeckel ( February 16, 1834 — August 9, 1919)also written von Haeckel, was an eminent German Kunstformen der Natur ( German: Art Forms of Nature) is a book of lithographic and Autotype prints by German biologist The crab at the centre is nursing the externa of the parasitic cirripede Sacculina
Thyrostraca, Cirrhopoda (meaning "tawny-footed"), Cirrhipoda, and Cirrhipedia. Sacculina is a Genus of Barnacles that parasitize Crabs The adults bear no resemblance to the barnacles that cover ships and piers Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " Structure of crustaceans As Arthropods crustaceans have a stiff Exoskeleton, which must be shed to allow the animal to grow ( Ecdysis or molting Maxillopoda is a class under the Phylum Arthropoda. It is also a class of Crustaceans (subphylum Crustacea) and the class is Thecostraca are a group of marine Invertebrates containing about 1320 described species Karl Hermann Konrad Burmeister ( January 15, 1807 - May 2, 1892) was a German Zoologist and Entomologist. This article is about the taxonomic rank for the sequence of species in a taxonomic list see Taxonomic order In scientific classification used Thoracica is a Superorder of Crustaceans which contains the most familiar species of Barnacles found on rocky Coasts such as Semibalanus Rhizocephala are peculiar Barnacles parasitic on decapod crustaceans In Scientific nomenclature, synonyms are different Scientific names used for a single Taxon.
A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence distantly related to crabs and lobsters. Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " In Zoology, an infraclass is a further subdivision of a subclass, but it is rarely used Taxonomic rank ( rank, category, taxonomic category is an abstract term used in the Scientific classification, or Taxonomy, of organisms Structure of crustaceans As Arthropods crustaceans have a stiff Exoskeleton, which must be shed to allow the animal to grow ( Ecdysis or molting Crabs are decapod Crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (βραχύ / brachy Clawed lobsters compose a family ( Nephropidae, sometimes also Homaridae) of large marine Crustaceans Lobsters are economically important as Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have two nektonic larval stages. Nekton refers to the aggregate of actively swimming aquatic organisms in a body of water (usually oceans or lakes able to move independently of water currents
Around 1,220 barnacle species are currently known. In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank.  The name "Cirripedia" is Latin, meaning "curl-footed".
Barnacles are encrusters, attaching themselves permanently to a hard substrate. The most common, "acorn barnacles" (Sessilia) are sessile, growing their shells directly onto the substrate. Sessilia is an order of Barnacles comprising the barnacles without stalks  The order Pedunculata ("goose barnacles" and others) attach themselves by means of a stalk. Goose barnacles (suborder Lepadomorpha) sometimes Gooseneck barnacles, are filter-feeding Crustaceans that live attached to hard surfaces of 
Most barnacles are suspension feeders; they dwell continually in their shell - which is usually constructed of six plates - and reach into the water column with modified legs. These feathery appendages beat rhythmically to draw plankton and detritus into the shell for consumption.
Other members of the class have quite a different mode of life. For example, members of the genus Sacculina are parasitic, dwelling within crabs. A genus (plural genera from Γένος Latin genus "descent family type gender" is a low-level Taxonomic Sacculina is a Genus of Barnacles that parasitize Crabs The adults bear no resemblance to the barnacles that cover ships and piers Parasitism is a type of symbiotic relationship between Organisms of different Species. 
Although they have been found at water depths up to 600m, most barnacles inhabit shallow waters, with 75% of species living in water depths of less than 100m, and 25% inhabiting the intertidal zone.  Within the intertidal zone, different species of barnacle live in very tightly constrained locations, allowing the exact height of an assemblage above or below sea level to be precisely determined. 
Since the intertidal zone periodically desiccates, barnacles are well adapted against water loss. Their calcite shells are impermeable, and they possess two plates which they can slide across their aperture when not feeding. These plates also protect against predation.
Barnacles are displaced by limpets and mussels, who compete for space. The name Limpet is used for many kinds of mostly saltwater but also freshwater Snails specifically those that have a simple shell which is more or less broadly conical The common name mussel is used for members of several different families of Clams or Bivalve Molluscs, from both saltwater and freshwater habitats They also have numerous predators. 
They employ two strategies to overwhelm their competitors: "swamping", and fast growth. In the swamping strategy, vast numbers of barnacles settle in the same place at once, covering a large patch of substrate, allowing at least some to survive in the balance of probabilities.  Fast growth allows the suspension feeders to access higher levels of the water column then their competitors, and to be large enough to resist displacement; species employing this response, such as the aptly named Megabalanus, can reach 7 cm in length; other species may grow larger still. Megabalanus is a genus of Barnacle. It grows to centimetres in length and inhabits the lower zone
Competitors may include other barnacles, and there is (disputed) evidence that balanoid barnacles competitively displaced chthalamoid barnacles. Balanoids gained their advantage over the chthalamoids in the Oligocene, when they evolved a tubular skeleton. This provides better anchorage to the substrate, and allows them to grow faster, undercutting, crushing and smothering by the latter group. 
Barnacles have 2 distinct larval stages, the nauplius and the cyprid, before developing into a mature adult. A nauplius (plural nauplii) is the first Larva of animals classified as Crustaceans (subphylum of Arthropoda) The barnacle cyprid (syn cypris larva is the final lecithotrophic Larval stage of Barnacles.
A fertilized egg hatches into a nauplius: a one eyed larva comprising a head and a telson, without a thorax or abdomen. This undergoes 6 molts before transforming into the bivalved cyprid stage. Nauplii are typically initially brooded by the parent, and released as free-swimming larvae after the first molt.
The cyprid stage lasts from days to weeks. The barnacle cyprid (syn cypris larva is the final lecithotrophic Larval stage of Barnacles. The barnacle cyprid (syn cypris larva is the final lecithotrophic Larval stage of Barnacles. During this part of the life cycle, the barnacle searches for a place to settle. It explores potential surfaces with modified antennules structures; once it has found a potentially suitable spot, it attaches head-first using its antennules, and a secreted glycoproteinous substance. Antennae (singular antenna) are paired Appendages connected to the front-most segments of Arthropods In Crustaceans they are Larvae are thought to assess surfaces based upon their surface texture, chemistry, relative wettability, colour and the presence/absence and composition of a surface biofilm; swarming species are also more likely to attach near to other barnacles. As the larva exhausts its finite energy reserves, so it becomes less picky in the sites it selects. If the spot is to its liking, it cementing down permanently with another proteinacous compound. This accomplished, it undergoes metamorphosis into a juvenile barnacle. Metamorphosis is a Biological process by which an Animal physically develops after Birth or hatching involving a conspicuous and relatively
Typical acorn barnacles develop six hard calcareous plates to surround and protect their bodies. Semibalanus balanoides is a common and widespread boreo - Arctic Species of Acorn barnacle. For the rest of their lives they are cemented to the ground, using their feathery legs (cirri) to capture plankton.
Once metamorphosis is over and they have reached their adult form, barnacles will continue to grow by adding new material to their heavily calcified plates. These plates are not moulted; however, like all ecdysozoans, the barnacle itself will still molt its cuticle. Ecdysis is the Molting of the Cuticula in Arthropods and related groups ( Ecdysozoa) The Ecdysozoa (ˌɛkdɪsəˈzoʊə are a grouping of Protostome animals including the Arthropoda ( Insects, Chelicerata, Crustaceans In Biology, the term cuticle or cuticula is given to a variety of tough but flexible non-mineral outer coverings of an organism or part of an organism that
Most barnacles are hermaphroditic, although a few species are gonochoric or androdioecious. A hermaphrodite is an organism having both male and female reproductive organs In Biology, gonochorism ( Greek offspring + disperse or unisexualism describes sexually reproducing species in which there are at Androdioecy is a reproductive system found in Species composed of a Male Population and a distinct Hermaphrodite population Typically, recently molted hermaphroditic individuals are receptive as females. Self-fertilization, although theoretically possible, has been experimentally shown to be rare in barnacles  .
The sessile lifestyle of barnacles makes sexual reproduction difficult, as the organisms cannot leave their shells to mate. The Evolution of sexual reproduction is a major puzzle The first Fossilized evidence of sexually reproducing Organisms is from Eukaryotes of the Stenian To facilitate genetic transfer between isolated individuals, barnacles have extraordinarily long penises, up to 15cm in length: the largest penis to body size ratio of the animal kingdom. The penis (plural penises, penes 
The geological history of barnacles can be traced back to the early Palaeozoic (in the order of 4-500 million years ago), although they do not become common in the fossil record until the Neogene (last 20 million years). The Neogene is a geologic period and system starting 2303 ± 0 In part their poor preservation is due to their restriction to high-energy environments, which tend to be erosional - therefore it is more common for their shells to be ground up by wave action than for them to reach a depositional setting. Erosion is the carrying away or displacement of solids ( Sediment, Soil, rock and other particles usually by the agents of currents such as wind It is also possible that the group was more minor in the past.
Barnacles can play an important role in estimating palæo-water depths. The degree of disarticluation of fossils suggests the distance they have been transported, and since many species have narrow ranges of water depths, it can be assumed that the animals lived in shallow water and broke up as they were washed down-slope. The completeness of fossils, and nature of damage, can thus be used to constrain the tectonic history of regions. 
Barnacles were first fully studied and classified by Charles Darwin who published a series of monographs in 1851 and 1854. Charles Robert Darwin (February 12 1809 &ndash April 19 1882 was an English naturalist, who realised and demonstrated that all Species of life A monograph ( Classical Greek, "One Writer" or "Single Writing") is a work of writing upon a single subject usually also by a single Darwin undertook this study at the suggestion of his friend Joseph Dalton Hooker, in order to thoroughly understand at least one species before making the generalisations needed for his theory of evolution by natural selection . Sir Joseph Dalton Hooker, OM, GCSI, MD, FRS (30 June 1817 – 10 December 1911 was an English Botanist and Explorer eVolution is the third Album by eLDee, it was due to be released in 2008 Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of
Barnacles are of economic consequence as they often attach themselves to man-made structures, sometimes to the structure's detriment. Particularly in the case of ships, they are classified as fouling organisms. Biofouling or biological fouling is the undesirable accumulation of Microorganisms Plants Algae and Animals on submerged structures
Some barnacles are edible by humans, and goose barnacles (e. Goose barnacles (suborder Lepadomorpha) sometimes Gooseneck barnacles, are filter-feeding Crustaceans that live attached to hard surfaces of g. Pollicipes polymerus) are treasured as a delicacy in many Mediterranean countries. The resemblance of this barnacle's fleshy stalk to a goose's neck gave rise in ancient times to the notion that geese, or at least certain seagoing species of wild goose, literally grew from the barnacle. Most notably, the wild Barnacle Goose (Branta leucopsis), whose eggs and young were rarely seen by humans because it breeds in the remote Arctic, got its popular name because it was imagined to grow from gooseneck barnacles. The Barnacle Goose ( Branta leucopsis) belongs to the Genus Branta of black geese, which contains Species with largely black The Arctic is the Region around the Earth 's North Pole, opposite the Antarctic region around the South Pole.
Some authorities regard Cirripedia as a full class or subclass, and the orders listed above are sometimes treated as superorders. A class is the Taxonomic rank in the Biological classification of organisms in Biology below phylum and above order. A class is the Taxonomic rank in the Biological classification of organisms in Biology below phylum and above order. This article is about the taxonomic rank for the sequence of species in a taxonomic list see Taxonomic order In scientific classification used This article follows Martin and Davis in placing Cirripedia as an infraclass of Thecostraca and in the following classification of cirripedes down to the level of orders :
Infraclass Cirripedia Burmeister, 1834