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A barnacle is a type of
arthropod An arthropod (, (gen. ποδός)) is an invertebrate animal having an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Euarthropoda,Reference showing that Euarthropoda is a phylum: ...
constituting the
infraclass In biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, ...
Cirripedia in the subphylum
Crustacea Crustaceans (Crustacea ) form a large, diverse arthropod An arthropod (, (gen. ποδός)) is an invertebrate animal having an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Eua ...
, and is hence related to
crab Crabs are Decapoda, decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen#Other animals, abdomen) ( el, :wikt:βραχύς, βραχύς , translit=brachys = short, / = tail), usually hid ...

crab
s and
lobster Lobsters are a family (biology), family (Nephropidae, sometimes also ''Homeridae'') of large marine crustaceans. Lobsters have long bodies with muscular tails, and live in crevices or burrows on the sea floor. Three of their five pairs of leg ...

lobster
s. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile (nonmobile) and most are suspension feeders, but those in superorder
Rhizocephala Rhizocephala are derived barnacle A barnacle is a type of arthropod An arthropod (, (gen. ποδός)) is an invertebrate animal having an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form ...
are parasitic. They have four
nekton Nekton or necton (from the ) refers to the actively swimming aquatic organisms in a body of water. The term was proposed by German biologist Ernst Haeckel Ernst Heinrich Philipp August Haeckel (; 16 February 1834 – 9 August 1919) was a Germ ...
ic (active swimming) larval stages. Around 1,000 barnacle
species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individu ...

species
are currently known. The name "Cirripedia" is
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, it became ...

Latin
, meaning "curl-footed". The study of barnacles is called cirripedology.


Description

Barnacles are encrusters, attaching themselves temporarily to a hard substrate. The most common, "acorn barnacles" (
Sessilia Sessilia is an order of barnacles, comprising the barnacles without stalks, or acorn barnacles. They form a monophyletic group and are probably derived from stalked barnacles. The order is divided into three suborders. The Brachylepadomorpha co ...
), are sessile, growing their shells directly onto the substrate. The order ''Pedunculata'' ( goose barnacles and others) attach themselves by means of a stalk. Free-living barnacles are attached to the substratum by cement glands that form the base of the first pair of
antennae Antenna (pl. antennas or antennae) may refer to: Science and engineering * Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves * Antennae Galaxies, the name of two coll ...
; in effect, the animal is fixed upside down by means of its forehead. In some barnacles, the cement glands are fixed to a long, muscular stalk, but in most they are part of a flat membrane or calcified plate. A ring of plates surrounds the body, homologous with the
carapace A carapace is a Dorsum (biology), dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tor ...
of other crustaceans. These consist of the rostrum, two lateral plates, two carinolaterals, and a carina. In sessile barnacles, the apex of the ring of plates is covered by an operculum, which may be recessed into the carapace. The plates are held together by various means, depending on species, in some cases being solidly fused. Inside the carapace, the animal lies on its stomach, with its limbs projecting downwards. Segmentation is usually indistinct, and the body is more or less evenly divided between the head and
thorax The thorax or chest is a part of the anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Bioc ...

thorax
, with little, if any,
abdomen The abdomen (colloquially called the belly, tummy, midriff or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the Trunk (anatomy) ...

abdomen
. Adult barnacles have few appendages on their heads, with only a single, vestigial pair of antennae, attached to the cement gland. The eight pairs of thoracic limbs are referred to as "cirre", which are feathery and very long, being used to filter food, such as plankton, from the water and move it towards the mouth. Barnacles have no true
heart The heart is a muscular MUSCULAR (DS-200B), located in the United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' use ...

heart
, although a sinus close to the
esophagus The esophagus (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American E ...

esophagus
performs a similar function, with blood being pumped through it by a series of muscles. The blood vascular system is minimal. Similarly, they have no
gill A gill () is a respiratory organ that many aquatic Aquatic means relating to water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent ...
s, absorbing oxygen from the water through their limbs and the inner membrane of their carapaces. The excretory organs of barnacles are maxillary glands. The main sense of barnacles appears to be touch, with the hairs on the limbs being especially sensitive. The adult also has three photoreceptors (ocelli), one median and two lateral. These photoreceptors record the stimulus for the barnacle shadow reflex, where a sudden decrease in light causes cessation of the fishing rhythm and closing of the opercular plates. The photoreceptors are likely only capable of sensing the difference between light and dark. This eye is derived from the primary .


Life cycle

Barnacles have two distinct larval stages, the nauplius and the cyprid, before developing into a mature adult.


Nauplius

A hatches into a nauplius: a one-eyed larva comprising a head and a
telson Image:Penaeus diagram telson.png, upright=1.4, Diagram highlighting the telson of the prawn ''Litopenaeus setiferus'' The telson is the posterior-most division of the body of an arthropod. Depending on the definition, the telson is either consider ...
, without a thorax or abdomen. This undergoes six moults, passing through five
instar An instar (, from the Latin ''īnstar'', "form", "likeness") is a developmental stage of arthropods An arthropod (, (gen. ποδός)) is an invertebrate Invertebrates are animals that neither possess nor develop a vertebral column (commonly ...
s, before transforming into the cyprid stage. Nauplii are typically initially brooded by the parent, and released after the first moult as larvae that swim freely using
seta In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...

seta
e.


Cyprid

The cyprid larva is the last larval stage before adulthood. It is not a feeding stage; its role is to find a suitable place to settle, since the adults are sessile. The cyprid stage lasts from days to weeks. It explores potential surfaces with modified antennules; once it has found a potentially suitable spot, it attaches head-first using its antennules and a secreted glycoproteinous substance. Larvae assess surfaces based upon their surface texture, chemistry, relative wettability, color, and the presence or absence and composition of a surface
biofilm A biofilm comprises any Syntrophy, syntrophic consortium of microorganisms in which cell (biology), cells cell adhesion, stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix th ...

biofilm
; swarming species are also more likely to attach near other barnacles. As the larva exhausts its finite energy reserves, it becomes less selective in the sites it selects. It cements itself permanently to the substrate with another proteinaceous compound, and then undergoes
metamorphosis Metamorphosis is a biological process Biological processes are those processes that are vital for an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are ...
into a juvenile barnacle.


Adult

Typical acorn barnacles develop six hard calcareous plates to surround and protect their bodies. For the rest of their lives, they are cemented to the substrate, using their feathery legs (cirri) to capture plankton. Once metamorphosis is over and they have reached their adult form, barnacles continue to grow by adding new material to their heavily calcified plates. These plates are not moulted; however, like all
ecdysozoa Ecdysozoa () is a group of protostome animals, including Arthropod An arthropod (, (gen. ποδός)) is an invertebrate animal having an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the ...

ecdysozoa
ns, the barnacle itself will still moult its
cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non-homology (biology), homologous, differing in the ...
.


Sexual reproduction

Most barnacles are
hermaphroditic In reproductive biology, a hermaphrodite () is an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life#Biology, properties of life ...

hermaphroditic
, although a few species are gonochoric or
androdioeciousAndrodioecy is a sexual reproduction, reproductive system characterized by the coexistence of males and hermaphrodites. Androdioecy is rare in comparison to the other major reproductive systems: dioecy, gynodioecy and hermaphroditism. In animals, an ...
. The ovaries are located in the base or stalk, and may extend into the mantle, while the testes are towards the back of the head, often extending into the thorax. Typically, recently moulted 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 Sexual reproduction is a type of reproduction Reproduction (or procreation or breeding) is the biological process Biological processes are those processes that are vital for an organism In biology, an organism (from Ancient Greek, ...
difficult, as the organisms cannot leave their shells to mate. To facilitate genetic transfer between isolated individuals, barnacles have extraordinarily long
penis A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during Copulation (zoology), copulation. Such organs occur in many animals, both #Vertebrates, vertebrate ...

penis
es⁠. Barnacles probably have the largest penis to body size ratio of the animal kingdom, up to eight times their body length. Barnacles can also reproduce through a method called spermcasting, in which the male barnacle releases his sperm into the water and females pick it up and fertilise their eggs. The
Rhizocephala Rhizocephala are derived barnacle A barnacle is a type of arthropod An arthropod (, (gen. ποδός)) is an invertebrate animal having an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form ...
superorder used to be considered hermaphroditic, but it turned out that its males inject themselves into the female's body, degrading to the condition of nothing more than sperm-producing cells.


Ecology

Most barnacles are suspension feeders; they dwell continually in their shells, which are usually constructed of six plates, and reach into the water column with modified legs. These feathery appendages beat rhythmically to draw
plankton Plankton are the diverse collection of organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology ...

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
superorder In biological classification, the order ( la, ordo) is # a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also re ...
Rhizocephala Rhizocephala are derived barnacle A barnacle is a type of arthropod An arthropod (, (gen. ποδός)) is an invertebrate animal having an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form ...
, including the
genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circumscribing) and classifying gr ...
''
Sacculina ''Sacculina'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a ...
'', are
parasitic Parasitism is a Symbiosis, symbiotic biological interactions, relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is adaptation (biology), ad ...

parasitic
and live within crabs. Although they have been found at water depths to , most barnacles inhabit shallow waters, with 75% of species living in water depths less than , and 25% inhabiting the
intertidal zone The intertidal zone, also known as the foreshore or seashore, is the area above water level Water level, also known as gauge height or stage, is the elevation of the free surface of a sea, stream, lake or reservoir relative to a specified ve ...
. Within the intertidal zone, different species of barnacles 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 apertures when not feeding. These plates also protect against predation. Barnacles are displaced by
limpet Limpets are a group of aquatic snails that exhibit a conical gastropod shell, shell shape (patelliform) and a strong, muscular foot. Limpets are members of the class Gastropoda, but are polyphyletic, meaning the various groups called "limpets" ...
s and
mussel Mussel () is the used for members of several families of s, from saltwater and habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or ...

mussel
s, which compete for space. 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 than their competitors, and to be large enough to resist displacement; species employing this response, such as the aptly named '' Megabalanus'', can reach in length; other species may grow larger still (''
Austromegabalanus psittacus ''Austromegabalanus psittacus'', the giant barnacle or ' as it is known in Spanish Spanish may refer to: * Items from or related to Spain , * gl, Reino de España, * oc, Reiaume d'Espanha, , , image_flag = Bandera de España.svg ...
''). Competitors may include other barnacles, and disputed evidence indicates balanoid barnacles competitively displaced chthalamoid barnacles. Balanoids gained their advantage over the chthalamoids in the Oligocene, when they evolved tubular skeletons, which provide better anchorage to the substrate, and allow them to grow faster, undercutting, crushing, and smothering chthalamoids. Among the most common predators on barnacles are
whelk Whelk (also known as scungilli) is a common name that is applied to various kinds of sea snail. Although a number of whelks are relatively large and are in the family Buccinidae (the true whelks), the word ''whelk'' is also applied to some ot ...
s. They are able to grind through the calcareous exoskeletons of barnacles and feed on the softer inside parts.
Mussel Mussel () is the used for members of several families of s, from saltwater and habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or ...

Mussel
s also prey on barnacle larvae. Another predator on barnacles is the starfish species ''
Pisaster ochraceus ''Pisaster ochraceus'', generally known as the purple sea star, ochre sea star, or ochre starfish, is a common seastar Starfish or sea stars are star-shaped echinoderms belonging to the class (biology), class Asteroidea. Common usage frequen ...
''. File:CornishBarnacles.JPG, Barnacles and
limpet Limpets are a group of aquatic snails that exhibit a conical gastropod shell, shell shape (patelliform) and a strong, muscular foot. Limpets are members of the class Gastropoda, but are polyphyletic, meaning the various groups called "limpets" ...
s compete for space in the intertidal zone File:Entenmuscheln.jpg, Goose barnacles, with their cirri extended for feeding File:Chesaconcavus base detail.jpg, Underside of large ''Chesaconcavus'' sp. (
Miocene The Miocene ( ) is the first geological epoch In geochronology, an epoch is a subdivision of the geologic timescale that is longer than an age (geology), age but shorter than a period (geology), period. The current epoch is the Holocene Epoch of ...
) showing internal plates in bioimmured smaller barnacles
The anatomy of parasitic barnacles is generally simpler than that of their free-living relatives. They have no carapace or limbs, having only unsegmented sac-like bodies. Such barnacles feed by extending thread-like rhizomes of living cells into their hosts' bodies from their points of attachment.


History of taxonomy

Barnacles were originally classified by
Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblement, ennoblement as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomi ...

Linnaeus
and
Cuvier Jean Léopold Nicolas Frédéric, Baron Cuvier (; 23 August 1769 – 13 May 1832), known as Georges Cuvier, was a French naturalist Natural history is a domain of inquiry involving organism In biology, an organism () is any orga ...

Cuvier
as
Mollusca Mollusca is the second-largest phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number ...

Mollusca
, but in 1830
John Vaughan Thompson John Vaughan Thompson Fellow of the Linnean Society, FLS (November 19, 1779 – January 21, 1847) was a British military surgeon, marine biologist, zoologist, botanist, and published naturalist. Early years John Vaughan Thompson was born in Briti ...
published observations showing the metamorphosis of the nauplius and cypris larvae into adult barnacles, and noted how these larvae were similar to those of crustaceans. In 1834
Hermann Burmeister Karl Hermann Konrad Burmeister (also known as Carlos Germán Conrado Burmeister) (15 January 1807 – 2 May 1892) was a German Argentine zoologist, entomologist, herpetologist, botany, botanist, and coleopterologist. He served as a professor at the ...
published further information, reinterpreting these findings. The effect was to move barnacles from the
phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number. The plural of a noun typically denotes a q ...
of Mollusca to Articulata, showing naturalists that detailed study was needed to reevaluate their
taxonomy Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a specific classification scheme. Originally used only about biological ...
.
Charles Darwin Charles Robert Darwin (; ; 12 February 1809 – 19 April 1882) was an English naturalist Natural history is a domain of inquiry involving organism In biology, an organism () is any organic, life, living system that fu ...

Charles Darwin
took up this challenge in 1846, and developed his initial interest into a major study published as a series of
monographs A monograph is a specialist work of writing (in contrast to reference works) or exhibition on a single subject or an aspect of a subject, often by a single author or artist, and usually on a scholarly subject. In library cataloging, ''monograp ...
in 1851 and 1854. Darwin undertook this study, at the suggestion of his friend
Joseph Dalton Hooker Sir Joseph Dalton Hooker (30 June 1817 – 10 December 1911) was a United Kingdom of Great Britain and Ireland, British botanist and explorer in the 19th century. He was a founder of geographical botany and Charles Darwin's closest friend ...

Joseph Dalton Hooker
, to thoroughly understand at least one species before making the generalisations needed for his theory of
evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; either through asexual reproduction or sexual reproduction, ...

evolution
by
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype right , Here the relation between genotype and phenotype is illustrated, using a Punnett square, for the character of peta ...
.


Classification

Some authorities regard the Cirripedia as a full
class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differently f ...
or subclass, and the orders listed above are sometimes treated as
superorder In biological classification, the order ( la, ordo) is # a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also re ...
s. In 2001, Martin and Davis placed Cirripedia as an infraclass of
Thecostraca Thecostraca is a Class (biology), subclass of marine invertebrates containing about 1,320 described species. Many species have planktonic larvae which become Sessility (zoology), sessile or parasite, parasitic as adults. The most important subgro ...
and divided it into six orders: Infraclass Cirripedia Burmeister, 1834 * Superorder Acrothoracica Gruvel, 1905 ** Order Pygophora Berndt, 1907 ** Order Apygophora Berndt, 1907 * Superorder
Rhizocephala Rhizocephala are derived barnacle A barnacle is a type of arthropod An arthropod (, (gen. ποδός)) is an invertebrate animal having an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form ...
Müller, 1862 ** Order Kentrogonida Delage, 1884 ** Order Akentrogonida Häfele, 1911 * Superorder Thoracica
Darwin Darwin most often refers to: * Charles Darwin (1809–1882), English naturalist and writer, best known as the originator of the theory of biological evolution by natural selection * Darwin, Northern Territory, a capital city in Australia * Darwin ( ...

Darwin
, 1854
** Order Pedunculata
Lamarck Jean-Baptiste Pierre Antoine de Monet, chevalier de Lamarck (1 August 1744 – 18 December 1829), often known simply as Lamarck (; ), was a French naturalist Natural history is a domain of inquiry involving organisms, including animals, fu ...

Lamarck
, 1818
** Order
Sessilia Sessilia is an order of barnacles, comprising the barnacles without stalks, or acorn barnacles. They form a monophyletic group and are probably derived from stalked barnacles. The order is divided into three suborders. The Brachylepadomorpha co ...
Lamarck, 1818


Fossil record

The geological history of barnacles can be traced back to animals such as '' Priscansermarinus'' from the
Middle Cambrian Middle or The Middle may refer to: * Centre (geometry), the point equally distant from the outer limits. Places * Middle (sheading), a subdivision of the Isle of Man * Middle Bay (disambiguation) * Middle Brook (disambiguation) * Middle Creek (di ...
(on the order of ), In A. J. Southward (ed.), 1987. although they do not become common as skeletal remains in the fossil record until the
Neogene The Neogene ( ) (informally Upper Tertiary or Late Tertiary) is a geologic period and system that spans 20.45 million years from the end of the Paleogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or E ...

Neogene
(last 20 million years). In part, their poor skeletal preservation is due to their restriction to high-energy environments, which tend to be
erosion In earth science Earth science or geoscience includes all fields of natural science Natural science is a branch of science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific ...

erosion
al – therefore it is more common for their shells to be ground up by wave action than for them to reach a depositional setting. Trace fossils of acrothoracican barnacle
boring Boring may refer to: *Something that causes boredom Engineering and science * Boring (earth), drilling a hole, tunnel, or well in the earth ** Tunnel boring machine, a machine used in boring tunnels * Boring (manufacturing), enlarging a hole tha ...
s ('' Rogerella'') are common in the fossil record from the
Devonian The Devonian ( ) is a geologic period and system of the Paleozoic The Paleozoic (or Palaeozoic) Era ( ; from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the H ...
to the recent. Barnacles can play an important role in estimating paleo-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. File:Balanus improvisus on Mya arenaria shell.jpg, '''', one of the many barnacle taxa described by
Charles Darwin Charles Robert Darwin (; ; 12 February 1809 – 19 April 1882) was an English naturalist Natural history is a domain of inquiry involving organism In biology, an organism () is any organic, life, living system that fu ...

Charles Darwin
File:Megabalanus on breccia.JPG,
Miocene The Miocene ( ) is the first geological epoch In geochronology, an epoch is a subdivision of the geologic timescale that is longer than an age (geology), age but shorter than a period (geology), period. The current epoch is the Holocene Epoch of ...
(
Messinian The Messinian is in the geologic timescale The geologic time scale (GTS) is a system of chronological datingChronological dating, or simply dating, is the process of attributing to an object or event a date in the past, allowing such object o ...
) '' Megabalanus'', smothered by sand and fossilised File:Chesaconcavus top view.jpg, ''Chesaconcavus'', a Miocene barnacle from Maryland


Relationship with humans

Barnacles are of economic consequence, as they often attach themselves to synthetic structures, sometimes to the structure's detriment. Particularly in the case of ships, they are classified as
fouling Fouling is the accumulation of unwanted material on solid surfaces. The fouling materials can consist of either living organisms (biofouling) or a non-living substance (inorganic or organic). Fouling is usually distinguished from other surfa ...
organisms. The amount and size of barnacles that cover ships can impair their efficiency by causing
hydrodynamic In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion and behavior through ...
drag Drag or The Drag may refer to: Places * Drag, Norway, a village in Tysfjord municipality, Nordland, Norway * ''Drág'', the Hungarian name for Dragu Commune in Sălaj County, Romania * Drag (Austin, Texas), the portion of Guadalupe Street adja ...
. Fortunately, this is not a problem for boats on inland waterways, as barnacles are exclusively marine. Uzun et al. (2020) provide a simplified approach for estimating the effect of real barnacle settlement in nature on the resistance and effective power of the ship. The stable
isotope Isotopes are two or more types of atoms that have the same atomic number 300px, The Rutherford–Bohr model of the hydrogen atom () or a hydrogen-like ion (). In this model it is an essential feature that the photon energy (or frequency) of ...
signals in the layers of barnacle shells can potentially be used as a forensic tracking method for
whale Whales are a widely distributed and diverse group of fully aquatic Aquatic means relating to water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is ...

whale
s,
loggerhead turtle The loggerhead sea turtle (''Caretta caretta''), is a of distributed throughout the world. It is a marine reptile, belonging to the . The average loggerhead measures around in length when fully grown. The adult loggerhead sea turtle weigh ...

loggerhead turtle
s and
marine debris Marine debris, also known as marine litter, is human-created waste Waste (or wastes) are unwanted or unusable materials. Waste is any substance which is discarded after primary use, or is worthless, defective and of no use. A by-produ ...

marine debris
, such as
shipwreck A shipwreck is the remains of a ship that has wrecked, which are found either beached on land or sunken to the bottom of a body of water. Shipwrecking may be deliberate or accidental. In January 1999, Angela Croome estimated that there have ...

shipwreck
s or a
flaperon A flaperon (a portmanteau A portmanteau (, ) or portmanteau word (from "Portmanteau (luggage), portmanteau") is a Blend word, blend of words
suspected to be from
Malaysia Airlines Flight 370 Malaysia Airlines Flight 370 (also known as MH370 or MAS370) was a scheduled international passenger flight operated by Malaysia Airlines that disappeared on 8 March 2014 while flying from Kuala Lumpur International Airport to its plan ...
. Some barnacles are considered edible by humans, including Japanese goose barnacles (''e.g.'' '' Capitulum mitella''), and goose barnacles (''e.g.'' ''Pollicipes pollicipes''), a delicacy in Spain and Portugal. The resemblance of this barnacle's fleshy stalk to a goose's neck gave rise, in ancient times, to the notion that geese literally grew from the barnacle. Indeed, the word "barnacle" originally referred to a species of goose, the barnacle goose ''Branta leucopsis'', whose eggs and young were rarely seen by humans because it breeds in the remote Arctic."...all the evidence shows that the name was originally applied to the ''bird'' which had the marvellous origin, not to the ''shell''..." Oxford English Dictionary, 2nd Edition, 1989 Additionally, the Austromegabalanus psittacus, picoroco barnacle is used in Chilean cuisine and is one of the ingredients in ''curanto''. File:Siuslaw River-1.jpg, Barnacles slowly reclaim pilings along the Siuslaw River in Oregon. File:Percebes.iguaria.jpg, Goose barnacle being enjoyed in a Spanish restaurant in Madrid


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Barnacles
from the Marine Education Society of Australasia

Article on barnacles in Spain, and their collection and gastronomy. * * * * {{Authority control Parasitic crustaceans Barnacles, Maxillopoda Articles containing video clips Extant Cambrian first appearances