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If you've heard someone called a barnacle, it means they're overly clingy.

What are barnacles? Barnacles are among the oldest living organisms on Earth and live in oceans around the world. It is a small crustacean that clings to hard surfaces on rocks, sea walls, boats, debris, land structures, and other marine animals such as turtles, sea snakes, lobsters, crabs, and whales. The arthropod is a member of the subphylum Crustacea, which includes crabs, lobsters, shrimps, prawns, crayfish, krill and psyllids.

It forms a symbiotic relationship with other marine animals, forming a layer of armor in return for being transported to plankton-rich waters for filter feeding. Edible gooseneck species are eaten by many people.


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6 Unbelievable Barnacle Facts!

  • It is one of the oldest living animals in the world.
  • It was once thought to be related to snails, which are mollusks because many species have hard shells.
  • It feeds with its lower legs, or feet, called "cirri" while levitating
  • Root barnacles are a parasite.
  • Symbiosis refers to a symbiotic relationship between a barnacle and another marine animal, in which the barnacle reaps most of the benefits.
  • It is androgynous.

Barnacles do not have a type species and therefore do not have a scientific name. Barnacles are members of the marine invertebrate class Maxillopod. The subclasses are Thecostraca, Tantulocarida, Branchiura, Pentastomida, Mystacocarida, Copepoda and Cirripedia. From Theocostraca, the Cirripedia subclass was divided into the superorder Thoracica, Acrothoracica and Rhizocephala, and then into 11 orders.

A glass bottle full of barnacles lies on the sand.
Barnacles are members of the marine invertebrate class Maxillopod.


Scientific names and types of barnacles

There are more than 14,000 species of barnacles, the most common being the acorn barnacle. However, many species have the common name of acorn barnacles. Scientific names for acorn barnacles can include the genera Balanus , Chthamalus , Megabalanus , Paraconcavus , or Semibalanus :

  • Common Acorn Barnacles ( Balanus glandula ) – These barnacles are common along the Pacific coast of North America and absorb oxygen from the air and water. Collectively, they are conical and live up to 10 years.
  • Giant Acorn Barnacle ( Balanus nubilus ) – True to its name, this is the largest barnacle in the world. They are found along the Pacific coast of North America, from Baja California to Alaska, in water depths up to 300 feet.
  • Acorn barnacles ( Chthamalus antennatus ) – also known as six-plate barnacles – these barnacles are found along the eastern and southern coasts of Australia.
  • Titan Acorn Barnacle ( Megabalanus coccopoma ) – This barnacle was first described by Charles Darwin. These can be found in South and Central America along the Pacific coast. They are a large conical barnacle.
  • Titan Acorn Barnacle ( Megabalanus tintinnabulum )
  • Red-striped acorn barnacle ( Paraconcavus pacificus ) – This is a glans-headed barnacle that grows to less than an inch and a half long. They have pink stripes with stripes on their plate growth rings.
  • Northern Acorn Barnacles ( Semibalanus balanoides ) – These are also known as common barnacles and northern rock barnacles. They are a very common version that can be found in rocky areas on the coasts of Western Europe, as well as on the western and eastern coasts of North America.
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Gooseneck barnacles, also known as stalked barnacles or goose barnacles, are also common. They are common names for members of the subclass Thoracica and order Pedunculata. The scientific names of gooseneck barnacles include the genera Pollicipes and Lepas .

  • Goose or leaf barnacle ( Polcipipes polymerus )
  • Gooseneck barnacles ( Pollicipes pollicipes ) – These are the stalked version of barnacles. They live on the rocky Pacific coast of North America, where they compete directly with other animals for limited living space.
  • Smooth gooseneck barnacles ( Lepas anatifera ) – Also known as pelagic gooseneck barnacles, these barnacles use their stems to attach to all types of driftwood, piers, ship hulls and floating objects.
A flock of goose barnacles with shells attached to wood by the sea.
The scientific names of gooseneck barnacles include the genera Pollicipes and Lepas .

© Ernie/Shutterstock.com

History and Evolution

Barnacles are among the oldest animals. They have lived for hundreds of millions of years, and the oldest fossils are over 300 million years old! About 20 million years ago, they evolved into something closer to their modern form.

Scientists were able to deduce information about water depths in prehistoric times based on barnacle fossils and evidence. They were able to do this by placing the finds and estimating how far they dipped down and deep into the ocean.


What are the characteristics of barnacles? A barnacle has specific anatomy depending on its species and whether it is in the larval stage of a nauplius or goldfish or a mature adult. Nauplius larvae hatch from fertilized eggs and have an eye, a head and telson, but no thorax or abdomen. It then goes through several molts to shed the cuticle, during which time it looks like a shrimp until they become juvenile adults.

Adult barnacles are 8.5 to 1 inch long and 0.5 to 1.5 inches tall, depending on the species. They are usually white, cream, yellow or black in color and their shells are bleached. Barnacles secrete 4 to 8 calcite plates, with an average of 6, to protect their soft bodies. Adult barnacles have little guts and no appendages to their anatomy other than legs or feet (called "cirri"), which they use for feeding and breathing. They have no heart or gills. There is no information about their weight, mainly the weight of their shells.

The barnacles attached to the hull, buoys and piers are volcanic, stony and gray in color. Gooseneck barnacles have a stalk to attach to a hard surface, but acorn barnacles do not and are cone-shaped. Acorn barnacles also have a "operculum" or opening at the top with a "door" of 2 or 4 additional plates, while gooseneck barnacles have a pinkish-white heart-shaped shell with black lines. Each type of barnacle has a different anatomy.

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The barnacles attached to the hull, buoys and piers are volcanic, stony and gray in color.

© Natursports/Shutterstock.com


The free-swimming and foraging behavior of a barnacle during its life cycle is often referred to as intertidal, referring to its long-term movement with ocean tides. When the tide comes, it opens its "door" panels and uses its tentacles to feed, closing its gill covers to conserve water. Many barnacles hibernate in winter, relying solely on their energy reserves.


Barnacle larvae swim freely for a short time after hatching from their eggs in order to find surfaces to attach to. It tends to settle where there are many other barnacles, which means they support life. The surface it colonizes must first have a film of algae, seaweed, bacteria, or diatoms in order for it to attach. Once it settles, it becomes fixed and may not move for life.

It lives on rocks, boats and marine life such as whales, fish and crustaceans in ocean waters worldwide. Because barnacles tend to encruste heavily on a boat, creating drag, and requiring pressure washing to remove, they are often referred to as "crusty fouling." When they pile up, they are said to be biofouling – meaning they are destroying it – and create drag.

Root barnacles live inside breastplate barnacles, mantis shrimp, and other crustaceans. Some non-parasitic barnacles attach to a site by growing their shells into the surface, while other species attach using superglue and peduncles (stems) first.

Because barnacles tend to encruste heavily on a boat, creating drag, and requiring pressure washing to remove, they are often referred to as "crusty fouling."

© Katopia/Creative Commons


The barnacle's food is plankton and detritus (dead organic particles), which it consumes through suspension feeding and filter feeding. It uses its extending and retracting tentacles to push food inside, and it opens its gill cover to let water in, then it closes its gill cover. The barnacle's diet is omnivorous, as it eats both plants and animals.

Barnacles are often called "encrusted polluters" because of their tendency to crust over boats in large numbers, causing drag.


Predators and Threats

Barnacles pose many threats, including competition for space with other barnacles. Other predators include mussels, starfish, limpets, whelks, and other sea snails. Barnacles are especially vulnerable to predators during the larval stage of their life cycle. If you keep barnacles as pets, there is a good chance that other animals in the aquarium will prey on them.

Barnacles are also considered a delicacy by some, for example in Spain, Portugal and other European countries. Barnacles of the order Pudenculata (goosenecks) are edible and have fleshy stems. The barnacles are scrubbed and steamed in a broth with herbs and wine, then the barnacles are peeled and served with the soup. Acorn barnacles are not edible because of the low amount of flesh on their stalks and the high level of accumulated toxins.

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Gooseneck barnacles are edible and have a fleshy stem.

© Shell World/Shutterstock.com

Reproduction, Babies and Longevity

Barnacles are hermaphrodites but cannot reproduce by self-fertilization and need to colonize with other barnacles in order to reproduce and be near a food source. When ready to reproduce, one barnacle begins to receive gametes from another, which has a long penis that can extend 6 to 8 inches.

The life cycle of a new barnacle begins as an egg, goes through two larval stages, and then grows from juvenile to full adult. Barnacles have a mantle cavity in which hundreds of eggs can be hatched at a time, and up to six broods can be incubated each year. The eggs overwinter inside the sac and hatch into small barnacles called larvae. The first larval stage, called Nauplius, swims freely for 6 months, after which the larvae transform into the second larval stage, Cyprid, which lasts anywhere from a few days to a few weeks. During this time, the baby goldfish will look for suitable surfaces to attach to. It then secretes a sticky glue from cement glands at the base of its antennae, begins to form a hard shell, and transforms into a juvenile adult. Barnacles reach sexual maturity at two years of age.

The lifespan of a barnacle depends on its species. Its lifespan can range from 18 months to 10 years or more, but averages 5 to 10 years.

Barnacles foraging underwater in Canada's St. Lawrence River
The life cycle of a new barnacle begins with an egg, two larval stages, and then the larvae into full adulthood.

© RLS Photo/Shutterstock.com


Barnacles do not move once attached to a surface or host, so they are especially vulnerable to the environment. Certain barnacle species are threatened, endangered, or nationally endangered. One threat is coastal pollution from garbage dumps, plastics, industrial runoff, chemical spills, sewage and livestock. Other threats include mangrove felling and deep-sea trawling to plunder underwater mountains, causing them to lose their habitat.

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Barnacles are omnivores, which means they eat both plants and other animals.

Barnacles belong to the animal kingdom.

Barnacles belong to the phylum Arthropoda.

Barnacles belong to the class Crustacea.

Barnacles belong to the family Thecostraca.

Barnacles belong to the class Maxillopod.

The barnacles are covered with shells.

Barnacles live in shallow sea environments.

The barnacles are attached to a hard surface, and the shell is made of plates.

Barnacles eat plankton and algae.

Predators of barnacles include fish, crabs, and humans.

Barnacles typically lay 1,000 eggs.

Barnacles can live for 8 to 20 years.

The optimum pH for barnacles is between 4.0 and 6.5.

A barnacle is a small crustacean that lives in the ocean.

It looks like shrimp but is either shelled or naked.

Yes, they are harmful to ships and buildings. Their destructive behavior is called "biofouling".

From its name alone, barnacles are sticky and difficult to remove. It hatches from the egg, floats around and goes through two larval stages before finding a suitable surface to attach to. Then it starts turning into a juvenile, then a juvenile-adult, after which it probably doesn't move for the rest of its life. Barnacles cannot move on their own, as larvae float freely in tidal movements.

Yes, the gooseneck barnacle is edible, it has a fleshy stalk.