Balanus balanus
Encyclopedia
Balanus balanus is a species
of acorn barnacle
in the Balanidae
family. It is native to the colder seas of the northern hemisphere.
s, barnacles are unable to move from place to place. Cement glands near the base of the antennae
fix them to the rock. The carapace
of this species is conical with a circular base which has an irregular edge and a diameter of up to three centimetres. The surface is ridged and white or pale brown. The cover plates protecting the opening are shaped like the beak of a bird.
, boulders, pebbles and shells. It seems to favour habitats with strong currents and when overcrowding occurs, adopts different shapes to fit the space available. It is often found growing alongside another barnacle, Balanus crenatus
. Other species often found in its vicinity include Tubularia larynx
, Obelia geniculata
, Pomatoceros triqueter
, Pecten maximus
, Hydroides norvegica
, Chlamys opercularis
and Sertularia
species. Coralline algae
was often present as were the whelk
, the European edible sea urchin
(Echinus esculentus), the great spider crab
(Hyas araneus) and the shore crab (Carcinus maenas
).
The main predator
is the juvenile common starfish
(Asterias rubens). Medium sized barnacles seem to be at greatest risk. Small specimens are ignored while large specimens seem able to withstand attack.
and the more northerly seas of the northern hemisphere. It has been introduced to Argentina where it is displacing other species and is considered invasive
.
in about April and attach themselves to objects on the sea floor. The newly metamorphosed
cyprid develops slowly reaching 1 millimetre (0.0393700787401575 in) diameter in a few weeks and 7 mm (0.275590551181102 in) by September. The growth rate then slows over the winter so that the year old barnacle averages 8 mm (0.31496062992126 in). Thereafter it grows at 5 millimetre a year and the largest specimens, 30 millimetre across are probably four to six years old. Under experimental conditions of total submersion growth is faster and more nearly resemble growth rates of Semibalanus balanoides
and Balanus crenatus
. This may be because these barnacles, being always under water, have a greater continuity of food supply. There is a wide variation in rate of growth and the factors affecting it include currents and nutrient content. A scarcity of diatom
s in mid-summer may slow growth at this time.
B. balanus is a cross-fertilising hermaphrodite
and the single brood of nauplii is produced in the middle of winter. In mature individuals (barnacles at least ten millimetres in diameter) the white vesiculae seminales
are very much enlarged at this time and filled with spermatozoa
, occupying much of the body cavity and the penis
is also greatly enlarged. At the same time, a creamy mass of eggs
are present in the ovarian tubules
. Fertilisation takes place over the course of a few days in each group of barnacles and the fertilised eggs change to an orange colour and then to a greyish-brown as the nauplii develop. New ovaries begin to form soon after fertilisation, and the testes re-develop during the summer with the size of the penis being reduced. After about forty days of embryonic development, the nauplii are liberated into the water. Many first year specimens are not fully mature in their first winter but those that are liberate 3,000 to 4,000 nauplii. Second year individuals at an average size of twenty millimetres will produce about 20,000 nauplii, whilst larger individuals of thirty millimetres may produce over 100,000.
The nauplii feed, moult
five times and swim with their antennae
. It takes about one month for them to develop into the cyprid larvae, the non-feeding stage before adulthood.
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
Barnacle
A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have...
in the Balanidae
Balanidae
Balanidae is a family of barnacles of the order Sessilia.- Genera :* †Alessandriella Carriol, 2001* Amphibalanus Pitombo, 2004* Arossia Newman, 1982* Austromegabalanus Newman, 1979* Balanus Da Costa, 1778* †Concavus Newman, 1982...
family. It is native to the colder seas of the northern hemisphere.
Description
Unlike most crustaceanCrustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s, barnacles are unable to move from place to place. Cement glands near the base of the 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....
fix them to the rock. The 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...
of this species is conical with a circular base which has an irregular edge and a diameter of up to three centimetres. The surface is ridged and white or pale brown. The cover plates protecting the opening are shaped like the beak of a bird.
Ecology
This species is found at depths of up to 60 metres (196.9 ft) and grows on bedrockBedrock
In stratigraphy, bedrock is the native consolidated rock underlying the surface of a terrestrial planet, usually the Earth. Above the bedrock is usually an area of broken and weathered unconsolidated rock in the basal subsoil...
, boulders, pebbles and shells. It seems to favour habitats with strong currents and when overcrowding occurs, adopts different shapes to fit the space available. It is often found growing alongside another barnacle, Balanus crenatus
Balanus crenatus
Balanus crenatus is a species of acorn barnacle in the Balanidae family. It is found in the North Pacific and the North Atlantic Ocean.-Description:...
. Other species often found in its vicinity include Tubularia larynx
Tubularia
Tubularia is a genus of hydroids that appear to be furry pink tufts or balls at the end of long strings, thus causing them to be sometimes be called "pink-mouthed" or "pink-hearted" hydroids. T. larynx is described as:The stems are tubular, with a yellowish coloured tegument and are branched at the...
, Obelia geniculata
Obelia
Obelia is a genus in the class Hydrozoa, which consists of mainly marine and some freshwater animal species and have both the polyp and medusa stages in their life cycle...
, Pomatoceros triqueter
Pomatoceros triqueter
Pomatoceros triqueter is a species of tube-building annelid worm in the class Polychaeta. It is common on the north eastern coasts of the Atlantic Ocean and in the Mediterranean Sea....
, Pecten maximus
Pecten maximus
Pecten maximus, common name the "great scallop" or "king scallop", is a species of scallop, an edible saltwater clam, a marine bivalve mollusc in the family Pectinidae, the scallops.This is the type species of the genus....
, Hydroides norvegica
Hydroides norvegica
Hydroides norvegica is a species of tube-forming annelid worm in the family Serpulidae. It is found on submerged rocks, shells, piles and boats in many coastal areas around the world. It is the type species of the genus Hydroides....
, Chlamys opercularis
Queen scallop
The Queen Scallop, scientific name Aequipecten opercularis, is a medium-sized species of scallop, an edible marine bivalve mollusk in the family Pectinidae, the scallops.-Description:...
and Sertularia
Air fern
Neptune plant or Air fern is a name given to a product that is composed of a species of marine animal called Sertularia argentea, also known as the "sea fir"....
species. Coralline algae
Coralline algae
Coralline algae are red algae in the order Corallinales. They are characterized by a thallus that is hard because of calcareous deposits contained within the cell walls...
was often present as were the whelk
Buccinum undatum
Buccinum undatum, known as the common whelk, is a large edible marine gastropod in the family Buccinidae, the "true whelks".-Distribution:...
, the European edible sea urchin
European Edible Sea Urchin
Echinus esculentus, the European edible sea urchin or common sea urchin, is a species of marine invertebrate in the Echinidae family. It is found in coastal areas of northwestern Europe down to a depth of 1200 metres. It is considered "Near threatened" in the IUCN Red List of Threatened...
(Echinus esculentus), the great spider crab
Great spider crab
The great spider crab, Hyas araneus, is a species of crab found in Atlantic waters and the North Sea, usually below the tidal zone.In 2003 it was discovered around the Antarctic Peninsula apparently transported by human agency....
(Hyas araneus) and the shore crab (Carcinus maenas
Carcinus maenas
Carcinus maenas is a common littoral crab, and an important invasive species, listed among the 100 "world's worst alien invasive species". It is native to the north-east Atlantic Ocean and Baltic Sea, but has colonised similar habitats in Australia, South Africa, South America and both Atlantic and...
).
The main predator
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
is the juvenile common starfish
Common starfish
The Common Starfish or Common Sea Star is the most common and familiar starfish in the north-east Atlantic. It has five arms and usually grows to between 10–30 cm across, although larger specimens are known. The Common Starfish is usually orange or brown, and sometimes violet;...
(Asterias rubens). Medium sized barnacles seem to be at greatest risk. Small specimens are ignored while large specimens seem able to withstand attack.
Distribution
Balanus balanus is found in the Arctic OceanArctic Ocean
The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest and shallowest of the world's five major oceanic divisions...
and the more northerly seas of the northern hemisphere. It has been introduced to Argentina where it is displacing other species and is considered invasive
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
.
Biology
Larvae settle out of the zooplanktonZooplankton
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"...
in about April and attach themselves to objects on the sea floor. The newly metamorphosed
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...
cyprid develops slowly reaching 1 millimetre (0.0393700787401575 in) diameter in a few weeks and 7 mm (0.275590551181102 in) by September. The growth rate then slows over the winter so that the year old barnacle averages 8 mm (0.31496062992126 in). Thereafter it grows at 5 millimetre a year and the largest specimens, 30 millimetre across are probably four to six years old. Under experimental conditions of total submersion growth is faster and more nearly resemble growth rates of Semibalanus balanoides
Semibalanus balanoides
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.-Description:...
and Balanus crenatus
Balanus crenatus
Balanus crenatus is a species of acorn barnacle in the Balanidae family. It is found in the North Pacific and the North Atlantic Ocean.-Description:...
. This may be because these barnacles, being always under water, have a greater continuity of food supply. There is a wide variation in rate of growth and the factors affecting it include currents and nutrient content. A scarcity of diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...
s in mid-summer may slow growth at this time.
B. balanus is a cross-fertilising hermaphrodite
Hermaphrodite
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...
and the single brood of nauplii is produced in the middle of winter. In mature individuals (barnacles at least ten millimetres in diameter) the white vesiculae seminales
Seminal vesicle
The seminal vesicles or vesicular glands are a pair of simple tubular glands posteroinferior to the urinary bladder of male mammals...
are very much enlarged at this time and filled with spermatozoa
Spermatozoon
A spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote...
, occupying much of the body cavity and the penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...
is also greatly enlarged. At the same time, a creamy mass of eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
are present in the ovarian tubules
Ovary
The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...
. Fertilisation takes place over the course of a few days in each group of barnacles and the fertilised eggs change to an orange colour and then to a greyish-brown as the nauplii develop. New ovaries begin to form soon after fertilisation, and the testes re-develop during the summer with the size of the penis being reduced. After about forty days of embryonic development, the nauplii are liberated into the water. Many first year specimens are not fully mature in their first winter but those that are liberate 3,000 to 4,000 nauplii. Second year individuals at an average size of twenty millimetres will produce about 20,000 nauplii, whilst larger individuals of thirty millimetres may produce over 100,000.
The nauplii feed, moult
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...
five times and swim with their 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....
. It takes about one month for them to develop into the cyprid larvae, the non-feeding stage before adulthood.