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Science & Nature • Marine Biology

Barnacle

Barnacles are marine crustaceans in the group Cirripedia, known for living attached to hard surfaces and feeding by filtering particles from the water.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 26, 2026|2 min read| Fact-checked

Barnacles are marine crustaceans in the group Cirripedia, known for living attached to hard surfaces and feeding by filtering particles from the water. Most species are free-living marine animals, while some are parasitic on other crustaceans. They are closely related to crabs, lobsters, and shrimp.

Classification

Barnacles are marine crustaceans in the subclass Cirripedia. They are more closely related to crabs, lobsters, and shrimp than to molluscs.

Anatomy and feeding

Adult barnacles are typically enclosed in hard calcium carbonate plates and feed by extending cirri, feathery appendages that capture suspended food particles from the water.

Life cycle

Barnacles begin as free-swimming larvae, including nauplius and cypris stages. After settlement, they permanently attach to a surface and transform into sessile adults.

Habitat and ecology

Barnacles are especially abundant on rocks, docks, pilings, boats, and other hard surfaces in coastal waters. They are an important part of intertidal ecosystems and food webs.

Key facts

  • Barnacles are crustaceans that spend most of their adult lives fixed to surfaces.
  • They attach using a strong natural cement and often build hard calcareous shells.
  • Their feathery cirri sweep plankton and other particles from the water for food.
  • Barnacles are most common in marine environments, especially in the intertidal zone.
  • Some barnacles live as internal parasites of other crustaceans.
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Canadian context

Barnacles are common along Canadian coasts, including the Atlantic, Pacific, and Arctic marine environments, where they are part of intertidal and nearshore ecosystems.

Frequently asked questions

Are barnacles animals or plants?
Barnacles are animals. They are marine crustaceans, not plants or shellfish in the botanical sense.
What do barnacles eat?
Barnacles are filter feeders that eat plankton and other small particles suspended in the water.
How do barnacles attach to surfaces?
Barnacles secrete a strong cement-like substance that anchors them permanently to hard surfaces.
Do barnacles move?
Adult barnacles are sessile and do not move from place to place, but their larvae swim freely before settling.
Are barnacles related to crabs?
Yes. Barnacles are crustaceans and are closely related to crabs, lobsters, and shrimp.

References

  1. Encyclopaedia Britannica — https://www.britannica.com/animal/barnacle
    Supports: Barnacles as marine crustaceans in Cirripedia; species diversity; parasitic and free-living forms.
  2. NOAA Ocean Service — https://oceanservice.noaa.gov/facts/barnacles.html
    Supports: Barnacles as crustaceans related to crabs, lobsters, and shrimps.
  3. Woods Hole Oceanographic Institution — https://www.whoi.edu/ocean-learning-hub/ocean-topics/ocean-life/barnacles/
    Supports: Attachment, feeding with cirri, larval settlement, and ecological role.
  4. PubMed — https://pubmed.ncbi.nlm.nih.gov/22821583/
    Supports: Specialized barnacle biology, calcified shell, and parasitic species.