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Cirripedi

Barnacles are crustaceans that, in their most common forms, stay permanently attached to a surface as adults. 1 2 They include three large, very different groups, with filter-feeding forms and parasitic forms. 1 3 On the reef, some species live embedded in the skeleton of hard corals. 4

Cirripedi

At a glance

Data from the scientific sources listed at the bottom.

Conservation

NEDDLCNTVUENCREWEX

IUCN Red List: not evaluated.

Where it lives

The sources read do not give a distribution for the whole group. There are 93 coral-dwelling species worldwide; the genus Cantellius, for example, is found only in the Indo-Pacific. 4 5

How to recognise it

Tap a number on the photo: the key explains what to look for.

12
  1. 1Cirri the appendages it feeds with, here extended 4
  2. 2Shell flush with the coral it stays at the same level as the coral, which often grows over it 4

Life in the wild

Where it is found

The sources read do not describe a habitat common to the whole group. Coral-dwelling species have a cup-shaped base embedded in the skeleton of the host coral and a shell flush with the surface; the coral tissue often grows over the shell. 4 Some live on a single coral species, others on many. 4 5

What it eats

WoRMS classes them as filter feeders, but this does not apply to all. 1 Coral barnacles feed mainly on what is suspended in the water, and also obtain organic substances produced by the coral's zooxanthellae. 4 The exceptions are the Rhizocephala, which absorb nutrients from inside their host, and the genus Hoekia, which feeds on an outgrowth of the coral Hydnophora. 3 6

Behaviour

The cyprid walks over surfaces on two adhesive discs before choosing where to attach. 2 In Pyrgoma cancellatum it settles at once on the right coral, without exploring. 4

Reproduction

The life cycle has four stages: nauplius, cyprid, juvenile and adult. 2 The nauplius passes through six phases; the cyprid explores surfaces, attaches with a cement and changes into a juvenile. 2 The larvae of some coral species settle only on the right host. 4

In the aquarium

From the experience of the BallingMania community.

Community rating

No rating in the original sheet.

Original sheet

Barnacles are an infraclass of marine crustaceans that attach permanently to rocks and other marine organisms such as corals.

They are parasitic organisms that attach to their host without causing harm, and they have long feathery filaments (the cirri) which they extend to filter the water and catch plankton and suspended particles, or snap back in if they sense danger. Barnacles have a fleshy mantle made of strong calcareous plates that protect them from predators.

They often attach to SPS or LPS corals in a kind of symbiosis that brings no advantage to the coral; in any case no damage has been observed in corals hosting barnacles. There are about a thousand species in the wild, and their size ranges from 0.5 to 5 cm. good or bad?

VERDICT:

Key: Good! An organism beneficial to the system. Reef Safe!

An organism whose benign or harmful nature is not yet known, to be kept an eye on.

Bad! The organism is a threat to the other inhabitants of the aquarium or could become a pest.

A food source for the other inhabitants of the aquarium.

A potentially toxic or venomous organism.

© Marc Levenson · © Pwnm30rdi3

Did you know?

The adult stays glued to the bottom even after death; its cement, under the calcareous base, forms a layer only a few micrometres thick. 2
In coral-dwelling species the ammonium released by the barnacle is absorbed by the zooxanthellae: this is why the relationship is considered beneficial to both. 4
Adult Rhizocephala have lost almost all their crustacean features: they do not kill their host, but they block its reproduction. 3

Sources

  1. WoRMS Editorial Board (2026). Cirripedia Burmeister, 1834. World Register of Marine Species.
  2. Liang, C.; Strickland, J.; Ye, Z.; Wu, W.; Hu, B.; Rittschof, D. (2019). Biochemistry of barnacle adhesion: an updated review. Frontiers in Marine Science 6: 565.
  3. Nagler, C.; Hörnig, M.K.; Haug, J.T.; Noever, C.; Høeg, J.T.; Glenner, H. (2017). The bigger, the better? Volume measurements of parasites and hosts: parasitic barnacles (Cirripedia, Rhizocephala) and their decapod hosts. PLoS ONE 12(7): e0179958.
  4. Yap, F.C.; Chen, H.N.; Chan, B.K.K. (2023). Host specificity and adaptive evolution in settlement behaviour of coral-associated barnacle larvae (Cirripedia: Pyrgomatidae). Scientific Reports 13.
  5. Kim, H.K.; Chan, B.K.K.; Song, S.J.; Khim, J.S. (2021). DNA-based diversity assessment reveals a new coral barnacle, Cantellius alveoporae sp. nov. (Balanomorpha: Pyrgomatidae) exclusively associated with the high latitude coral Alveopora japonica in the waters of southern Korea. PeerJ 9: e11284.
  6. Ross, A.; Newman, W.A. (1995). A coral-eating barnacle, revisited (Cirripedia, Pyrgomatidae). Contributions to Zoology 65(3): 129-175.

Sources checked on 5 November 2026. Community texts and ratings are kept separate from the scientific data.

Download the original sheet (Italian)All species