Semibalanus balanoides
Encyclopedia
Semibalanus balanoides 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
.
, living attached to rocks and other solid substrates. They have six greyish wall plates surrounding a diamond-shaped
operculum
. The base of the shell is membranous
in Semibalanus, unlike other barnacles which have calcified
bases. When the tide rises to cover the barnacles, the operculum opens, and feathery cirri (modified thoracic appendage
s) are extended into the water to filter food
from the seawater. When the tide falls, the operculum closes again to prevent desiccation
; the reduction from the primitive condition
of eight wall plates to six is believed to decrease water loss even further by reducing the number of sutures through which water can escape.
in the world's northern ocean
s. Its distribution is limited in the north by the extent of the pack-ice
and in the south by increasing temperature which prevents maturation of gamete
s. The mean monthly temperature
of the sea must drop below 7.2 °C (45 °F) for it to breed.
In Europe
, S. balanoides is found on Svalbard
and from Finnmark
to north-west Spain
but excluding part of the Bay of Biscay
. It is common throughout the British Isles
, except in parts of Cornwall
, the Scilly Isles and south-western Ireland
. On the North America
n coast of the Atlantic Ocean
, it reaches as far south as Cape Hatteras
, North Carolina
, and on the Pacific coast
, it reaches as far south as British Columbia
. S. balanoides is the most common and widespread intertidal barnacle in the British Isles, and the only intertidal barnacle of the north-east coast of North America.
, although with some overlap. S. balanoides can tolerate salinities
down to 20 psu, allowing it to colonise parts of estuaries
. On semi-exposed shores, S. balanoides may form a patchwork with patches of seaweed
s, such as Fucus serratus, and limpet
s; the frond
s of the seaweeds brush the barnacle larvae from the rocks, allowing limpets to colonise it instead. At the southern limit of its range, including Cornwall
, S. balanoides is replaced by Chthamalus montagui
. Although capable of living in the sublittoral zone
, S. balanoides tends to be restricted to the intertidal by predation and by competition from species such as the blue mussel
, Mytilus edulis, and the algae Ascophyllum nodosum
and Chondrus crispus.
, using its thoracic
appendage
s, or cirri, to capture zooplankton
and detritus
from the water. If there is a current, then the barnacle holds its cirri stiffly into the flow, but when there is no current, the barnacle beats its cirri rhythm
ically. Plankton levels are highest in Spring and Autumn, and drop significantly during Winter, when the barnacles are dependent on reserves of food which they have stored.
, but cannot fertilise
itself. Gamete
s are transferred with a penis
which may be up to 7.5 centimetres (3 in) long; barnacles that are further apart than about 5 cm (2 in) are therefore unable to reproduce together. 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. Up to 10,000 eggs may be produced, and they are stored in sacs within the shell cavity. While the eggs are developing, the adult barnacle does not moult. The eggs hatch into nauplius larvae, which have three pairs of legs
, one pair of antennae
and a single eye
and are released to coincide with the spring algal bloom
. These spend several weeks in the water column, feeding on plankton
. Over a series of moults
, the larva passes through six naupliar instar
s before changing into a cypris larva, with a two-valved carapace
. These larvae can survive weeks embedded in sea ice
. The cypris larva does not feed but seeks out a suitable substrate for its adult life. Having settled on a substrate, the larva examines the area until it finds another barnacle of the same species and then attaches itself to the substrate with its antennae, whereupon it metamorphoses
into the adult. Sexual maturity is usually only reached after two years, and adults of S. balanoides may live for up to seven years, depending on their position on the shore.
Nucella lapillus
, the shanny Lipophrys pholis
, the sea star
Asterias vulgaris, and nudibranch
s. Although they have no eye
s, barnacles are aware of changes in light, and withdraw into their shells when threatened. Parasites of S. balanus include Pyxinoides balani, a protozoa
n which lives in the barnacle's midgut, and Epistylis horizontalis, a ciliate
which lives on the gill
s. The isopod Hemioniscus balani
occurs from France
to the Faroe Islands
and the Oslofjord
, and from Labrador
to Massachusetts
, and is a parasite of S. balanoides, effectively castrating
the barnacle if it is heavily infested. The lichen
s Arthropyrenia sublittoralis and Pyrenocollema halodytes may colonise the shells of barnacles.
Boreal ecosystem
The term boreal is usually applied to ecosystems localized in subarctic and subantarctic zones, although Austral is also used for the latter....
-arctic
Arctic
The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...
species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of acorn barnacle. It is common on rocks and other substrates in the intertidal zone
Intertidal zone
The intertidal zone is the area that is above water at low tide and under water at high tide . This area can include many different types of habitats, with many types of animals like starfish, sea urchins, and some species of coral...
of north-western Europe
North-West Europe
North-West Europe is a term that refers to a northern area of Western Europe, although the exact area or countries it comprises varies.-Geographic definition:...
and both coasts of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
.
Description
Adult S. balanoides grow up to 15 millimetre (0.590551181102362 in) in diameter, and are sessileSessility (zoology)
In zoology, sessility is a characteristic of animals which are not able to move about. They are usually permanently attached to a solid substrate of some kind, such as a part of a plant or dead tree trunk, a rock, or the hull of a ship in the case of barnacles. Corals lay down their own...
, living attached to rocks and other solid substrates. They have six greyish wall plates surrounding a diamond-shaped
Rhombus
In Euclidean geometry, a rhombus or rhomb is a convex quadrilateral whose four sides all have the same length. The rhombus is often called a diamond, after the diamonds suit in playing cards, or a lozenge, though the latter sometimes refers specifically to a rhombus with a 45° angle.Every...
operculum
Operculum (gastropod)
The operculum, meaning little lid, is a corneous or calcareous anatomical structure which exists in many groups of sea snails and freshwater snails, and also in a few groups of land snails...
. The base of the shell is membranous
Biological membrane
A biological membrane or biomembrane is an enclosing or separatingmembrane that acts as a selective barrier, within or around a cell. It consists of a lipid bilayer with embedded proteins that may constitute close to 50% of membrane content...
in Semibalanus, unlike other barnacles which have calcified
Calcification
Calcification is the process in which calcium salts build up in soft tissue, causing it to harden. Calcifications may be classified on whether there is mineral balance or not, and the location of the calcification.-Causes:...
bases. When the tide rises to cover the barnacles, the operculum opens, and feathery cirri (modified thoracic appendage
Appendage
In invertebrate biology, an appendage is an external body part, or natural prolongation, that protrudes from an organism's body . It is a general term that covers any of the homologous body parts that may extend from a body segment...
s) are extended into the water to filter food
Filter feeder
Filter feeders are animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feeding are clams, krill, sponges, baleen whales, and many fish and some sharks. Some birds,...
from the seawater. When the tide falls, the operculum closes again to prevent desiccation
Desiccation
Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic substance that induces or sustains such a state in its local vicinity in a moderately sealed container.-Science:...
; the reduction from the primitive condition
Primitive (biology)
Primitive in the sense most relevant to phylogenetics means resembling the first living things and in particular resembling them in the simple nature of their anatomy and behaviour...
of eight wall plates to six is believed to decrease water loss even further by reducing the number of sutures through which water can escape.
Distribution
S. balanoides is found in the intertidal zoneIntertidal zone
The intertidal zone is the area that is above water at low tide and under water at high tide . This area can include many different types of habitats, with many types of animals like starfish, sea urchins, and some species of coral...
in the world's northern ocean
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
s. Its distribution is limited in the north by the extent of the pack-ice
Polar ice packs
Polar ice packs are large areas of pack ice formed from seawater in the Earth's polar regions, known as polar ice caps: the Arctic ice pack of the Arctic Ocean and the Antarctic ice pack of the Southern Ocean, fringing the Antarctic ice sheet. Polar packs significantly change their size during...
and in the south by increasing temperature which prevents maturation of gamete
Gamete
A gamete is a cell that fuses with another cell during fertilization in organisms that reproduce sexually...
s. The mean monthly temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
of the sea must drop below 7.2 °C (45 °F) for it to breed.
In Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, S. balanoides is found on Svalbard
Svalbard
Svalbard is an archipelago in the Arctic, constituting the northernmost part of Norway. It is located north of mainland Europe, midway between mainland Norway and the North Pole. The group of islands range from 74° to 81° north latitude , and from 10° to 35° east longitude. Spitsbergen is the...
and from Finnmark
Finnmark
or Finnmárku is a county in the extreme northeast of Norway. By land it borders Troms county to the west, Finland to the south and Russia to the east, and by water, the Norwegian Sea to the northwest, and the Barents Sea to the north and northeast.The county was formerly known as Finmarkens...
to north-west Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
but excluding part of the Bay of Biscay
Bay of Biscay
The Bay of Biscay is a gulf of the northeast Atlantic Ocean located south of the Celtic Sea. It lies along the western coast of France from Brest south to the Spanish border, and the northern coast of Spain west to Cape Ortegal, and is named in English after the province of Biscay, in the Spanish...
. It is common throughout the British Isles
British Isles
The British Isles are a group of islands off the northwest coast of continental Europe that include the islands of Great Britain and Ireland and over six thousand smaller isles. There are two sovereign states located on the islands: the United Kingdom of Great Britain and Northern Ireland and...
, except in parts of Cornwall
Cornwall
Cornwall is a unitary authority and ceremonial county of England, within the United Kingdom. It is bordered to the north and west by the Celtic Sea, to the south by the English Channel, and to the east by the county of Devon, over the River Tamar. Cornwall has a population of , and covers an area of...
, the Scilly Isles and south-western Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
. On the North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
n coast of the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
, it reaches as far south as Cape Hatteras
Cape Hatteras
Cape Hatteras is a cape on the coast of North Carolina. It is the point that protrudes the farthest to the southeast along the northeast-to-southwest line of the Atlantic coast of North America...
, North Carolina
North Carolina
North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...
, and on the Pacific coast
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
, it reaches as far south as British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
. S. balanoides is the most common and widespread intertidal barnacle in the British Isles, and the only intertidal barnacle of the north-east coast of North America.
Ecology
S. balanoides can be the dominant species of rocky shores, where it grows in a range of situations, from very sheltered to very exposed. It is typically found lower on the shore than another barnacle, Chthamalus montaguiChthamalus montagui
Chthamalus montagui, common name Montagu's stellate barnacle, is a species of acorn barnacle common on rocky shores in South West England, Ireland, and Southern Europe.The vertical distribution of C...
, although with some overlap. S. balanoides can tolerate salinities
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
down to 20 psu, allowing it to colonise parts of estuaries
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
. On semi-exposed shores, S. balanoides may form a patchwork with patches of seaweed
Seaweed
Seaweed is a loose, colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae...
s, such as Fucus serratus, and limpet
Limpet
Limpet is a common name for a number of different kinds of saltwater and freshwater snails ; it is applied to those snails that have a simple shell which is more or less conical in shape, and either is not spirally coiled, or appears not to be coiled in the adult snails.The name limpet is most...
s; the frond
Frond
The term frond refers to a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group...
s of the seaweeds brush the barnacle larvae from the rocks, allowing limpets to colonise it instead. At the southern limit of its range, including Cornwall
Cornwall
Cornwall is a unitary authority and ceremonial county of England, within the United Kingdom. It is bordered to the north and west by the Celtic Sea, to the south by the English Channel, and to the east by the county of Devon, over the River Tamar. Cornwall has a population of , and covers an area of...
, S. balanoides is replaced by Chthamalus montagui
Chthamalus montagui
Chthamalus montagui, common name Montagu's stellate barnacle, is a species of acorn barnacle common on rocky shores in South West England, Ireland, and Southern Europe.The vertical distribution of C...
. Although capable of living in the sublittoral zone
Neritic zone
The neritic zone, also called coastal waters, the coastal ocean or the sublittoral zone, is the part of the ocean extending from the low tide mark to the edge of the continental shelf, with a relatively shallow depth extending to about 200 meters...
, S. balanoides tends to be restricted to the intertidal by predation and by competition from species such as the blue mussel
Blue mussel
The blue mussel, Mytilus edulis, is a medium-sized edible marine bivalve mollusc in the family Mytilidae. In spite of its specific name edulis, it is not the sole edible Mytilus species.-Distribution:...
, Mytilus edulis, and the algae Ascophyllum nodosum
Ascophyllum nodosum
Ascophyllum nodosum is a large, common brown alga in the family Fucaceae, being the only species in the genus Ascophyllum. It is seaweed of the northern Atlantic Ocean, also known as rockweed, Norwegian kelp, knotted kelp, knotted wrack or egg wrack...
and Chondrus crispus.
Feeding
Semibalanus balanoides is a filter feederFilter feeder
Filter feeders are animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feeding are clams, krill, sponges, baleen whales, and many fish and some sharks. Some birds,...
, using its thoracic
Thorax
The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
appendage
Appendage
In invertebrate biology, an appendage is an external body part, or natural prolongation, that protrudes from an organism's body . It is a general term that covers any of the homologous body parts that may extend from a body segment...
s, or cirri, to capture zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
and detritus
Detritus
Detritus is a biological term used to describe dead or waste organic material.Detritus may also refer to:* Detritus , a geological term used to describe the particles of rock produced by weathering...
from the water. If there is a current, then the barnacle holds its cirri stiffly into the flow, but when there is no current, the barnacle beats its cirri rhythm
Rhythm
Rhythm may be generally defined as a "movement marked by the regulated succession of strong and weak elements, or of opposite or different conditions." This general meaning of regular recurrence or pattern in time may be applied to a wide variety of cyclical natural phenomena having a periodicity or...
ically. Plankton levels are highest in Spring and Autumn, and drop significantly during Winter, when the barnacles are dependent on reserves of food which they have stored.
Reproduction
Breeding takes place in winter at an optimal temperature of 14 °C (57.2 °F). S. balanoides is hermaphroditicHermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...
, but cannot fertilise
Fertilisation
Fertilisation is the fusion of gametes to produce a new organism. In animals, the process involves the fusion of an ovum with a sperm, which eventually leads to the development of an embryo...
itself. Gamete
Gamete
A gamete is a cell that fuses with another cell during fertilization in organisms that reproduce sexually...
s are transferred with a penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...
which may be up to 7.5 centimetres (3 in) long; barnacles that are further apart than about 5 cm (2 in) are therefore unable to reproduce together. 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. Up to 10,000 eggs may be produced, and they are stored in sacs within the shell cavity. While the eggs are developing, the adult barnacle does not moult. The eggs hatch into nauplius larvae, which have three pairs of legs
Arthropod leg
The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa , trochanter , femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus ,...
, one pair of antennae
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
and a single eye
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
and are released to coincide with the spring algal bloom
Algal bloom
An algal bloom is a rapid increase or accumulation in the population of algae in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Typically, only one or a small number of phytoplankton species are involved, and some blooms may be recognized by discoloration...
. These spend several weeks in the water column, feeding on plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
. Over a series of moults
Ecdysis
Ecdysis is the moulting of the cuticula in many invertebrates. This process of moulting is the defining feature of the clade Ecdysozoa, comprising the arthropods, nematodes, velvet worms, horsehair worms, rotifers, tardigrades and Cephalorhyncha...
, the larva passes through six naupliar instar
Instar
An instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, or...
s before changing into a cypris larva, with a two-valved carapace
Carapace
A carapace is a dorsal 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 tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
. These larvae can survive weeks embedded in sea ice
Sea ice
Sea ice is largely formed from seawater that freezes. Because the oceans consist of saltwater, this occurs below the freezing point of pure water, at about -1.8 °C ....
. The cypris larva does not feed but seeks out a suitable substrate for its adult life. Having settled on a substrate, the larva examines the area until it finds another barnacle of the same species and then attaches itself to the substrate with its antennae, whereupon it metamorphoses
Metamorphosis
Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...
into the adult. Sexual maturity is usually only reached after two years, and adults of S. balanoides may live for up to seven years, depending on their position on the shore.
Parasites and predators
Predators of Semibalanus balanoides include the whelkWhelk
Whelk, also spelled welk or even "wilks", is a common name used to mean one or more kinds of sea snail. The species, genera and families referred to using this common name vary a great deal from one geographic area to another...
Nucella lapillus
Dog Whelk
The dog whelk, dogwhelk, or Atlantic dogwinkle, scientific name Nucella lapillus, is a species of predatory sea snail, a carnivorous marine gastropod mollusc in the family Muricidae, the rock snails....
, the shanny Lipophrys pholis
Lipophrys pholis
Lipophrys pholis is a species of combtooth blenny. It matures at two years of age. Distributed in the Eastern Atlantic from the southern Norway to Morocco and Madeira, including the Mediterranean and the Balearics. Lipophrys pholis feed primarily on crustaceans, but also feeds on plants and...
, the sea star
Sea star
Starfish or sea stars are echinoderms belonging to the class Asteroidea. The names "starfish" and "sea star" essentially refer to members of the class Asteroidea...
Asterias vulgaris, and nudibranch
Nudibranch
A nudibranch is a member of what is now a taxonomic clade, and what was previously a suborder, of soft-bodied, marine gastropod mollusks which shed their shell after their larval stage. They are noted for their often extraordinary colors and striking forms...
s. Although they have no eye
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
s, barnacles are aware of changes in light, and withdraw into their shells when threatened. Parasites of S. balanus include Pyxinoides balani, a protozoa
Protozoa
Protozoa are a diverse group of single-cells eukaryotic organisms, many of which are motile. Throughout history, protozoa have been defined as single-cell protists with animal-like behavior, e.g., movement...
n which lives in the barnacle's midgut, and Epistylis horizontalis, a ciliate
Ciliate
The ciliates are a group of protozoans characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagella but typically shorter and present in much larger numbers with a different undulating pattern than flagella...
which lives on the gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
s. The isopod Hemioniscus balani
Hemioniscus balani
Hemioniscus balani is a species of isopod crustacean that is a widespread parasitic castrator of barnacles in the north Atlantic Ocean. Its range extends from Norway to the Atlantic coast of France, and as far west as Massachusetts.-Life history:H...
occurs from France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
to the Faroe Islands
Faroe Islands
The Faroe Islands are an island group situated between the Norwegian Sea and the North Atlantic Ocean, approximately halfway between Scotland and Iceland. The Faroe Islands are a self-governing territory within the Kingdom of Denmark, along with Denmark proper and Greenland...
and the Oslofjord
Oslofjord
The Oslofjord is a bay in the south-east of Norway, stretching from an imaginary line between the Torbjørnskjær and Færder lighthouses and down to Langesund in the south to Oslo in the north....
, and from Labrador
Labrador
Labrador is the distinct, northerly region of the Canadian province of Newfoundland and Labrador. It comprises the mainland portion of the province, separated from the island of Newfoundland by the Strait of Belle Isle...
to Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
, and is a parasite of S. balanoides, effectively castrating
Parasitic castration
Parasitic castration is the strategy, by a parasite, of blocking reproduction by its host, completely or in part. For example, Hemioniscus balani, a parasitic castrator of hermaphroditic barnacles, feeds on ovarian fluid, so that its host loses female reproductive ability but still can function as...
the barnacle if it is heavily infested. The lichen
Lichen
Lichens are composite organisms consisting of a symbiotic organism composed of a fungus with a photosynthetic partner , usually either a green alga or cyanobacterium...
s Arthropyrenia sublittoralis and Pyrenocollema halodytes may colonise the shells of barnacles.