''Megabalanus'' is a genus of

barnacle 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 erosiv ...

s in the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Balanidae The Balanidae comprise a family of barnacles of the order Balanomorpha The Balanomorpha are an order of barnacles, containing familiar acorn barnacles of the seashore. The order contains these families: * Austrobalanidae Newman & Ross, 1976 ...

. Members of the genus grow to in length and inhabit the lower

intertidal zone The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species ...

Morphology

''Megabalanus'' is an

acorn barnacle Acorn barnacle and acorn shell are vernacular names for certain types of stalkless barnacles, generally excluding stalked or gooseneck barnacles. As adults they are typically cone-shaped, symmetrical, and attached to rocks or other fixed objects ...

, a sessile crustacean that secretes a calcium carbonate shell consisting of five plates. It reaches up to in height .

Ecology

Like other barnacles, they are

suspension feeder Filter feeders are a sub-group of suspension feeding 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 feedin ...

s, grabbing particulate matter from the water column overhead. ''M. tintinnabulum'' has a worldwide distribution and is commonly found on wave-beaten shores, in the lower intertidal zone. They tend to grow in clusters of around 12 individuals. Other species are more select, such as ''M. californicus'' of tidal habitats in

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

and the greater North American Pacific Coast. While many barnacles deal with competition for space by organisms such as limpets and mussels by growing many organisms close together in colonies, ''Megabalanus'' responds by rapidly growing to a very large size. Their large size also helps reduce

predation Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

, although it makes them large enough to be harvested for human consumption.

Geological utility

Fossilised specimens of ''Megabalanus'' have been found dating back to the

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

. Fossils bearing a close resemblance to ''M. tintinnabulum'' are preserved in large numbers in the Tabernas Basin of

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. A case study of this area showed that the state of preservation of the organisms makes possible estimating the distance they were transported ''post mortem'' . Since the species today lives in the intertidal zone, this allows an estimate to be made of the distance from the shoreline, and by implication, the water depth. These observations are backed up by the appearance of the deep-water trace fossil '' Zoophycum'' in the predicted deepest waters, suggesting that barnacles can be a good

proxy Proxy may refer to: * Proxy or agent (law), a substitute authorized to act for another entity or a document which authorizes the agent so to act * Proxy (climate), a measured variable used to infer the value of a variable of interest in climate re ...

for water depth.

Species

The World Register of Marine Species includes these species in the genus: * '' Megabalanus ajax'' (Darwin, 1854) * '' Megabalanus antillensis'' (Pilsbry, 1916) * '' Megabalanus azoricus'' (Pilsbry, 1916) (Azorean barnacle) * '' Megabalanus californicus'' (Pilsbry, 1916) (California barnacle) * '' Megabalanus clippertonensis'' Zullo, 1969 * '' Megabalanus coccopoma'' (Darwin, 1854) (titan acorn barnacle) * '' Megabalanus costatus'' (Hoek, 1913) * '' Megabalanus crispatus'' (Schröter) Darwin, 1854 * '' Megabalanus dolfusii'' (de Alessandri, 1907) * '' Megabalanus dorbignii'' (chenu, 1843) * '' Megabalanus galapaganus'' (Pilsbry, 1916) * '' Megabalanus giganteum'' (Kolosváry, 1949) * '' Megabalanus honti'' (Kolosváry, 1950) * '' Megabalanus hungaricus'' (Kolosváry, 1941) * '' Megabalanus javanicus'' (Whithers, 1923) * '' Megabalanus leganyii'' (Kolosváry, 1950) * '' Megabalanus linzei'' (Foster, 1978) * '' Megabalanus multiseptatus'' (Ross, 1964) * '' Megabalanus occator'' (Darwin, 1854) * '' Megabalanus peninsularis'' (Pilsbry, 1916) * '' Megabalanus plicatus'' (Hoek, 1913) * '' Megabalanus rosa'' Pilsbry, 1916 (acorn barnacle) * '' Megabalanus seguenzai'' (de Alessandri, 1895) * '' Megabalanus spinosus'' (Gmelin, 1791) * '' Megabalanus stultus'' (Darwin, 1854) * '' Megabalanus tanagrae'' (Pilsbry, 1928) * '' Megabalanus tintinnabulum'' ( Linnaeus, 1758) (titan acorn barnacle) * '' Megabalanus transsylvanicus'' (Kolosváry, 1950) * '' Megabalanus transversostriatus'' (Beurlen, 1958) * '' Megabalanus tulipiformis'' (Ellis, 1758) * '' Megabalanus validus'' Darwin, 1854 * '' Megabalanus venezuelensis'' (Weisbord, 1966) * '' Megabalanus vesiculosus'' (Darwin, 1854) * '' Megabalanus vinaceus'' (Darwin, 1854) * '' Megabalanus volcano'' (Pilsbry, 1916) * '' Megabalanus xishaensis'' (Ren & Liu, 1978) * '' Megabalanus zebra'' Russell et al., 2003

References

{{Taxonbar, from=Q3282981 Barnacles Extant Miocene first appearances