Cirripedia is the subclass for Barnacles, which are a type of invertebrate arthropod. Any of the greater than 1,000 mostly marine crustaceans of the Cirripedia subclass have undergone extensive sedentary life modification. Acorn Barnacles are the most prevalent of the more than 1,000 kinds of Barnacles that may be found in bodies of water across the globe.

Barnacles adhere to rough surfaces and other marine creatures including  It develops a symbiotic association with other marine creatures by constructing a layer of protection in exchange for being taken to regions with lots of plankton so it may employ filter feeding.


Depending on the species, Barnacles range in size from 1-9 inches in length and 0.5-1.5 inches in height. They generally have shells that are polished white and come in shades of cream, yellow, or black. To shield their fragile bodies, Barnacles produce calcite coatings, which are six layers on average.

Singular Barnacle specimen attached to wood
Singular Barnacle specimen attached to wood

The only anatomical appendages on adult Barnacles, known as “cirri,” are their feet, which they utilize for respiration and grazing. Mature Barnacles have hardly any inner organs. They lack gills and a heart. There is no information available on their exact weight, which is measured after the fact. Barnacles that encrust themselves on ship hulls and piers are rocky and gray in color.


A Barnacle consumes either both animal or plant matter, making its diet omnivorous. The majority of Barnacles are suspension feeders, as in they remain permanently inside their shells, which are typically made of 6 plates, and extend their modified legs into the water column. Plankton and necrotic organic materials make up the food of the Barnacle, which it eats by filtering and ingesting suspensions of these nutrients. It pushes the food inside using its cirri, which it stretches and retracts, then opens its opening to let water in before closing it again.


After emerging from the egg, the larval Barnacle swims freely for a brief while in search of a substrate to adhere to. It usually settles in locations where a large number of other barnacles exist, indicating that they are conducive to life. Before it can attach, the substrate it lands on must contain a layer of algal cells. 

Barnacle accumulation on dock legs
Barnacle accumulation on dock legs

Barnacles produce a fast-curing adhesive that is one of the strongest known natural glues, with tensile strengths of 5,000 pounds per square inch and adhesive strengths of 22 to 60 pounds per square inch. It becomes sessile after it settles and may not move again for the rest of its life.


Despite being hermaphrodites, Barnacles cannot breed through self-fertilization and must cohabit with other barnacles in order to both breed and feed. When one Barnacle is ready to procreate, the other extends a large penis that spans 6 to 8 inches that becomes receptive to its gametes. 

The Barnacle can have up to 6 hatchlings a year and lays hundreds of eggs once The eggs molt into larvae throughout the course of the winter inside the cavity. They scavenge for suitable sticking surfaces for a few weeks after the larval stage. A Barnacle’s life expectancy varies depending on its species. Its lifespan can range, on average; it lasts between 5-10 years.


A barnacle faces a variety of dangers, including rival barnacles seeking limited amounts of space. Mussels, starfish, limpets, whelks, and other types of sea snails are additional predators. The larval phases of the barnacle’s entire lifecycle are when it is most susceptible to predators. 

Barnacles attached to shore exposed rocks
Barnacles attached to shore exposed rocks

Barnacles are likely to be eaten by other aquarium inhabitants if they are maintained as pets. Worldwide consumption of some barnacle species is regarded as a delicacy. However, humans often scrape them off of ships and piers. The overall performance of ships in the water is negatively impacted by large barnacle populations, which raise their drag.

Facts about the Barnacle

  1. Barnacles produce the strongest natural glue in the world.
  2. Barnacles are hermaphroditic species.
  3. Barnacles use their feet to feed.
  4. Barnacles are a type of arthropod that is linked to crabs and lobsters.
  5. Barnacles spend all of their life fixed to a single position.


Are Barnacles harmful to humans?

Barnacles are permanently fixed to a surface for the rest of their lifespan; they possess no venom or teeth that would be harmful to humans. They can be consumed as well, making Barnacles completely harmless.

Do Barnacles fall off in freshwater?

During the winter, when manatees join the relatively warm springs, they enter freshwater bodies, where the Barnacles can’t survive in freshwater conditions, so they perish. They eventually come off, leaving a somewhat circular wound on the manatee’s back.

Do Barnacles hurt sharks?

Most Barnacles sift small food particles from the surrounding water as they rest on rough surfaces. Anelasma Squalicola, a particular species of Barnacle, makes an exception. Sharks are consumed by a parasitic Barnacle that attaches to their flanks and scavenges nourishment off their tissue, eventually taking chunks.

Why do they remove Barnacles from boats?

Algae, slime, and other marine life can stick to your boat’s hull during the warmer seasons, impairing its efficiency. One of the strategies to maintain a boat smooth and clear of marine debris is to remove Barnacles and periodically scrub the bottom.

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