| Balanus balanus | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Thecostraca |
| Subclass: | Cirripedia |
| Order: | Balanomorpha |
| Family: | Balanidae |
| Genus: | Balanus |
| Species: | B. balanus |
| Binomial name | |
| Balanus balanus | |
Balanus balanus is a species of acorn barnacle in the Balanidae family. It is native to the colder seas of the northern hemisphere.
Unlike most crustaceans, 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. [2]
This species is found at depths of up to 150 metres (490 ft), [3] commonly between 20 -- 30 metres [4] and grows on bedrock, boulders, pebbles and shells. [5] 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 ). [6]
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. [7] Other predators are snails, worms and birds. [8]
Balanus balanus is found in the Arctic Ocean 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.
Larvae settle out of the zooplankton in about April and attach themselves to objects on the sea floor. The newly metamorphosed cyprid develops slowly reaching 1 millimetre (0.039 in) diameter in a few weeks and 7 mm (0.28 in) by September. The growth rate then slows over the winter so that the year old barnacle averages 8 mm (0.31 in). Thereafter it grows at 5–10 mm (0.20–0.39 in) a year and the largest specimens, 30–40 mm (1.2–1.6 in) 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 diatoms in mid-summer may slow growth at this time. [6]
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. [6]
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. [9]
Barnacles are a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and are hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. Around 1,000 barnacle species are currently known.
Rhizocephala are derived barnacles that parasitise mostly decapod crustaceans, but can also infest Peracarida, mantis shrimps and thoracican barnacles, and are found from the deep ocean to freshwater. Together with their sister groups Thoracica and Acrothoracica, they make up the subclass Cirripedia. Their body plan is uniquely reduced in an extreme adaptation to their parasitic lifestyle, and makes their relationship to other barnacles unrecognisable in the adult form. The name Rhizocephala derives from the Ancient Greek roots ῥίζα and κεφαλή, describing the adult female, which mostly consists of a network of thread-like extensions penetrating the body of the host.
Cancer pagurus, commonly known as the edible crab or brown crab, is a species of crab found in the North Sea, North Atlantic Ocean, and perhaps the Mediterranean Sea. It is a robust crab of a reddish-brown colour, having an oval carapace with a characteristic "pie crust" edge and black tips to the claws. A mature adult may have a carapace width up to 25 centimetres and weigh up to 3 kilograms. C. pagurus is a nocturnal predator, targeting a range of molluscs and crustaceans. It is the subject of the largest crab fishery in Western Europe, centred on the coasts of the British Isles, with more than 60,000 tonnes caught annually.
Austrominius modestus is a species of barnacle in the family Elminiidae, native to Australia, Tasmania and New Zealand, but now spread to Britain and the north west coasts of Europe. It reaches a maximum size of about 10 millimetres in diameter.
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.
The common starfish, common sea star or sugar starfish is the most common and familiar starfish in the north-east Atlantic. Belonging to the family Asteriidae, 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 brownish in color, and sometimes violet; specimens found in deeper waters are pale. The common starfish is found on rocky and gravelly substrates where it feeds on mollusks and other benthic invertebrates.
Chthamalus stellatus, common name Poli's stellate barnacle, is a species of acorn barnacle common on rocky shores in South West England, Ireland, and Southern Europe. It is named after Giuseppe Saverio Poli.
Amphibalanus improvisus, the bay barnacle, European acorn barnacle, is a species of acorn barnacle in the family Balanidae.
Novocrania anomala is a species of brachiopod found offshore in the eastern Atlantic Ocean.
Balanus crenatus is a species of acorn barnacle in the Balanidae family. It is found in the North Pacific and the North Atlantic Ocean.
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.
Amphibalanus amphitrite is a species of acorn barnacle in the Balanidae family. Its common names include the striped barnacle, the purple acorn barnacle and Amphitrite's rock barnacle. It is found in warm and temperate waters worldwide.
Balanus perforatus is a species of barnacle in the family Balanidae. It is found on the lower shore and in the neritic zone in the warm temperate parts of the eastern Atlantic Ocean.
Pollicipes polymerus, commonly known as the gooseneck barnacle or leaf barnacle, is a species of stalked barnacle. It is found, often in great numbers, on rocky shores on the Pacific coasts of North America.
Megabalanus tintinnabulum is a species of large barnacle in the family Balanidae. It is the type species of the genus. The specific name comes from the Latin tintinnabulum meaning a handbell and probably refers to the fact that small groups of barnacles resemble clusters of miniature bells.
Amphibalanus eburneus, the ivory barnacle or American acorn barnacle, is a species of acorn barnacle in the family Balanidae. It occurs on the east coast of North America, the Caribbean Sea and Gulf of Mexico.
Leptasterias tenera is a species of starfish in the family Asteriidae. It is found on the eastern coast of North America.
Capitulum is a monotypic genus of sessile marine stalked barnacles. Capitulum mitella is the only species in the genus. It is commonly known as the Japanese goose barnacle or kamenote and is found on rocky shores in the Indo-Pacific region.
Coronula diadema is a species of whale barnacle that lives on the skin of humpback whales and certain other species of whale. This species was first described by Carl Linnaeus in the 1767 12th edition of his Systema Naturae.
Megabalanus californicus, the California barnacle, is a species of large barnacle in the family Balanidae. It is native to rocky coasts in the Eastern Pacific Ocean from North California to the Gulf of California.
