''Balanus perforatus'' is a species of barnacle in the family Balanidae. It is found on the lower shore and in the

neritic zone The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminated ...

in the warm temperate parts of the eastern Atlantic Ocean.

Description

''Balanus perforatus'' is a large barnacle which grows up to in both diameter and height. Its shape resembles a volcano with steep sloping sides. The six fused lateral calcareous plates are pale purplish-brown and often ridged vertically. They often separate near the top leaving jagged ridges. Tissue inside the operculum is brightly coloured. Two pairs of moveable plates cover the operculum which can be sealed by a purplish-brown flap when the barnacle is exposed above water or it is not feeding.European Marine Life
Retrieved July 19, 2011.Marine Life Information Network
Retrieved July 19, 2011.

Distribution

''Balanus perforatus'' is found on coastlines along the eastern side of the

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

including the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ...

and the

English Channel The English Channel, "The Sleeve"; nrf, la Maunche, "The Sleeve" (Cotentinais) or ( Jèrriais), (Guernésiais), "The Channel"; br, Mor Breizh, "Sea of Brittany"; cy, Môr Udd, "Lord's Sea"; kw, Mor Bretannek, "British Sea"; nl, Het Kana ...

. Its most northerly extent is in southern areas of

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

and

Wales Wales ( cy, Cymru ) is a country that is part of the United Kingdom. It is bordered by England to the east, the Irish Sea to the north and west, the Celtic Sea to the south west and the Bristol Channel to the south. It had a population in ...

, and at this limit of its range it can be greatly affected by severe winters. It has been expanding its range with the rises in temperature that have been occurring in recent decades. It is found on rocks and man-made structures from mid-shore to the

and also forms part of the

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 sur ...

community on the hulls of ships.

Biology

When submerged, ''B. perforatus'' extends its

cirri Giovanni Battista Cirri (1 October 1724 – 11 June 1808) was an Italian cellist and composer in the 18th century. Biography Cirri was born in Forlì in the Emilia-Romagna Region of Italy. He had his first musical training with his brother ...

and beats then rhythmically at a rate of between two and twenty-four beats per ten seconds. The cirri are less extended when the beat rate is faster. It feeds on plankton and as well as catching food particles, it pumps water through its mantle cavity. The faster the beating, the more water is pumped and the volume may reach one litre per hour. Slow beat rates are linked to pauses while the cirri are retracted rather than a reduction in the speed of movement of the cirri. ''B. perforatus'' is well adapted to life as an efficient current-producing suspension feeder. Breeding takes place between May and September in the English Channel when the quantity of planktonic food for the larvae is at its greatest. Initially the larvae are brooded by the adult and after their first moult are released into the

water column A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment.Munson, B.H., Axler, R., Hagley C., Host G., Merrick G., Richards C. (2004).Glossary. ''Water on the Web''. University of Minnesota-D ...

. There are five further nauplius stages during which the larvae feed, grow, moult, drift with the currents and form part of the

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

. The last stage

cyprid A barnacle is a type of arthropod constituting the subclass 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 ...

larvae then settle out and attach themselves to a suitable substrate.

Ecology

In the habitats occupied by ''B. perforatus'' it is often associated with

sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate throug ...

s and encrusting red seaweeds on shady overhanging rocks and cave entrances and also

bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a ...

ns and

ascidians Ascidiacea, commonly known as the ascidians, tunicates (in part), and sea squirts (in part), is a polyphyletic class in the subphylum Tunicata of sac-like marine invertebrate filter feeders. Ascidians are characterized by a tough outer "tunic" ...

in deeper shade. The isopod

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can ...

'' Crinoniscus equitans'' is an ectoparasite of ''B. perforatus''. Another isopod crustacean, '' Naesa bidentata'', normally lives in rock crevices and under seaweed and stones but with the spread of ''B. perforatus'', it has adopted the empty shells of the barnacle as its home.

References

{{Taxonbar, from=Q2880537 Barnacles Crustaceans of the Atlantic Ocean Crustaceans described in 1789