''Amphibalanus improvisus'', the bay barnacle, European acorn barnacle, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of acorn barnacle in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Balanidae The Balanidae is a family of barnacle Barnacles are arthropods of the subclass (taxonomy), subclass Cirripedia in the subphylum Crustacean, Crustacea. They are related to crabs and lobsters, with similar Nauplius (larva), nauplius larvae. Ba ...

Description

''Amphibalanus improvisus'' has a smooth white or pale grey conical calcareous shell composed of six fused plates. There is an oval or rhombic opening at the top which is blocked by two hinged plates. Adults usually grow to about in diameter and in width though they are sometimes larger than this and can grow taller when densely packed. The base is characteristically grooved radially. This species can be confused with the striped barnacle ('' Amphibalanus amphitrite'') and in European waters with the northern rock barnacle ('' Semibalanus balanoides'') or the rock barnacle ('' Balanus crenatus'').

Distribution

''Amphibalanus improvisus'' has a

cosmopolitan distribution In biogeography, a cosmopolitan distribution is the range of a taxon that extends across most or all of the surface of the Earth, in appropriate habitats; most cosmopolitan species are known to be highly adaptable to a range of climatic and en ...

and is found in temperate and tropical parts of the Atlantic Ocean, the Arctic Ocean, the Baltic Sea the North Sea, the Mediterranean Sea and the Black Sea. It is not known where the species natural range lies but it may have originated in North America. It has colonised many parts of the world's oceans including the Indo-Pacific and Australasia as a

biofouling Biofouling or biological fouling is the accumulation of microorganisms, plants, algae, or small animals where it is not wanted on surfaces such as ship and submarine hulls, devices such as water inlets, pipework, grates, ponds, and rivers that ...

agent on the hulls of

ship A ship is a large watercraft, vessel that travels the world's oceans and other Waterway, navigable waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research and fishing. Ships are generally disti ...

s. It was one of the first recorded introductions to the

Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by the countries of Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden, and the North European Plain, North and Central European Plain regions. It is the ...

, having been found in

Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...

and

Lithuania Lithuania, officially the Republic of Lithuania, is a country in the Baltic region of Europe. It is one of three Baltic states and lies on the eastern shore of the Baltic Sea, bordered by Latvia to the north, Belarus to the east and south, P ...

in 1844, the

Elbe The Elbe ( ; ; or ''Elv''; Upper Sorbian, Upper and , ) is one of the major rivers of Central Europe. It rises in the Giant Mountains of the northern Czech Republic before traversing much of Bohemia (western half of the Czech Republic), then Ge ...

estuary in 1854 and

Great Britain Great Britain is an island in the North Atlantic Ocean off the north-west coast of continental Europe, consisting of the countries England, Scotland, and Wales. With an area of , it is the largest of the British Isles, the List of European ...

in the 1880s.

Habitat

''Amphibalanus improvisus'' is found, sometimes in vast numbers, down to a depth of about on rocks, man made structures, buoys, ships' hulls, the shells of crabs and molluscs, and certain seaweeds. It has been known to block the water intake pipes of factories and power stations. It is tolerant of both high and low salinity levels and is often found in estuaries and low salinity bays. As an invasive species it competes with native organisms and it is an unwanted coloniser of the shells of cultivated oysters and mussels and aquaculture cages.

Biology

''Amphibalanus improvisus'' is a

filter feeder Filter feeders are aquatic animals that acquire nutrients by feeding on organic matters, food particles or smaller organisms (bacteria, microalgae and zooplanktons) suspended in water, typically by having the water pass over or through a s ...

. It extends its six pairs of modified legs called cirri to catch

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

and other organic material floating past. It is a

hermaphrodite A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many ...

and sperm is passed into the cavity of a neighbouring barnacle through a long penis. The eggs are fertilised and brooded in the cavity and hatch into nauplius larvae which drift with the currents. After six naupliar stages occupying two to five weeks, these become cyprid larvae and find a suitable surface on which to settle. Here they cement themselves to the

substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (aquatic environment), the earthy material that exi ...

and undergo

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and different ...

into juveniles. There may be several broods in the year but usually just two in the cooler waters of the Baltic and only one in low salinity environments.

Control

Marine paints may contain an

antifouling Biofouling or biological fouling is the accumulation of microorganisms, plants, algae, or small animals where it is not wanted on surfaces such as ship and submarine hulls, devices such as water inlets, pipework, grates, ponds, and rivers that ...

substance, the free base form of medetomidine, sold as Selektope. The anti-settling effect against the barnacle has been shown in vitro: When the barnacle cyprid larva encounters a surface containing medetomidine the molecule interacts with the octopamine receptor in the larva. This causes the settling larva to increase its kicking to more than 100 kicks per minute, which makes becoming sessile nearly impossible.

References

External links

''Balanus improvisus''
European Network on Invasive Species * {{Authority control Barnacles Crustaceans described in 1854 Taxa named by Charles Darwin