''Megabalanus'' is a genus 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. Barnacles are exclusively marine invertebra ...

s 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 ...

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

intertidal zone The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various ...

Morphology

''Megabalanus'' is an acorn barnacle, a sessile crustacean that secretes a

calcium carbonate Calcium carbonate is a chemical compound with the chemical formula . It is a common substance found in Rock (geology), rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skel ...

shell consisting of five plates. It reaches up to in height .

Ecology

Like other barnacles, they are

suspension 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 spec ...

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 U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

and the greater North American Pacific Coast. While many barnacles deal with competition for space by organisms such as

limpet Limpets are a group of aquatic snails with a conical gastropod shell, shell shape (patelliform) and a strong, muscular foot. This general category of conical shell is known as "patelliform" (dish-shaped). Existing within the class Gastropoda, ...

s and

mussel Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and Freshwater bivalve, freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other ...

s 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 in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

, 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 epoch (geology), 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 mea ...

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

Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...

. 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 A trace fossil, also called an ichnofossil (; ), is a fossil record of biological activity by lifeforms, but not the preserved remains of the organism itself. Trace fossils contrast with body fossils, which are the fossilized remains of part ...

'' Zoophycum'' in the predicted deepest waters, suggesting that barnacles can be a good proxy 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 ''Megabalanus coccopoma'', the titan acorn barnacle, is a tropical species of barnacle first described by Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English Natural history#Before 1900, natu ...

'' ( 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 Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

1758 Events January–March * January 1 – Swedish biologist Carl Linnaeus (Carl von Linné) publishes in Stockholm the first volume (''Animalia'') of the 10th edition of ''Systema Naturae'', the starting point of modern zoologic ...

) (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 yamaguchii'' Karasawa & Kobayashi, 2025 * '' Megabalanus zebra'' Russell et al., 2003

References

{{Authority control Barnacles Extant Miocene first appearances