''Balanus nubilus'', commonly called the giant acorn barnacle, is the world's largest

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 ...

, reaching a diameter of and a height of up to , and containing the largest known

muscle fibre A muscle cell, also known as a myocyte, is a mature contractile cell in the muscle of an animal. In humans and other vertebrates there are three types: skeletal, smooth, and cardiac (cardiomyocytes). A skeletal muscle cell is long and threadlike ...

Classification

''Balanus nubilus'' was named by

Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English Natural history#Before 1900, naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all speci ...

, who described its appearance and noted its habitat. He wrote that the barnacles were found on rotting wood and were associated with ''

Balanus glandula ''Balanus glandula'' (commonly known as the North American acorn barnacle or common acorn barnacle) is one of the most common barnacle species on the Pacific coast of North America, distributed from the U.S. state of Alaska to Bahía de San Quin ...

''. Darwin said the barnacles were "very distinct" but thought that the species allied with ''

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. Description Unlike most crustaceans, barnacles are unable to move from place to place. Cement glands near the ...

'' more closely "than to any other species", and also allied with '' B. cariosus''.

Ecology

''Balanus nubilus'' is a northeast Pacific species that ranges from southern

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

Baja California Baja California, officially the Free and Sovereign State of Baja California, is a state in Mexico. It is the northwesternmost of the 32 federal entities of Mexico. Before becoming a state in 1952, the area was known as the North Territory of B ...

. It is frequently found growing on rocks,

pier A pier is a raised structure that rises above a body of water and usually juts out from its shore, typically supported by piling, piles or column, pillars, and provides above-water access to offshore areas. Frequent pier uses include fishing, b ...

pilings and hard-shelled animals at depths of up to . Like other

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 ...

s, ''B. nubilus'' is a

filter 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 s ...

; it, in turn, is sometimes eaten by

sea otter The sea otter (''Enhydra lutris'') is a marine mammal native to the coasts of the northern and eastern Pacific Ocean, North Pacific Ocean. Adult sea otters typically weigh between , making them the heaviest members of ...

sea star Starfish or sea stars are Star polygon, star-shaped echinoderms belonging to the class (biology), class Asteroidea (). Common usage frequently finds these names being also applied to brittle star, ophiuroids, which are correctly referred to ...

crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...

s and the Native Americans of the

Pacific Northwest The Pacific Northwest (PNW; ) is a geographic region in Western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though no official boundary exists, the most common ...

. Abandoned shells of ''B. nubilus'' are used by the crab ''

Glebocarcinus oregonensis ''Glebocarcinus oregonensis'', commonly known as the pygmy rock crab, is a species of crab found on the Pacific coast of North America. Description It is usually red/brown but this may vary; their legs have many setae (hairs). The carapace reach ...

'' for shelter.

References

Barnacles Crustaceans of the eastern Pacific Ocean Crustaceans described in 1854 Taxa named by Charles Darwin {{Maxillopoda-stub