Bryan McAllister’s personal reference notebook
July 30, 2026Short & citedBlog
Civic Viewpoint.
A quiet encyclopedia with a personal desk
Kept by Bryan McAllister — short guides, clear facts, and the Canadian angle when it matters.
Field Notes • 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.

Updated July 30, 20261 min readCited sources

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

What it is

Barnacles belong to the subclass Cirripedia and are crustaceans, not molluscs. More than 1,000 species exist, most living in marine environments. Adults are sessile and encased in hard calcium carbonate plates.

How it feeds and attaches

Barnacles are filter feeders. They extend feathery cirri to sweep plankton and other particles from the water. They permanently attach to surfaces using a strong natural cement, often on rocks, docks, and boat hulls.

Life cycle and habitat

Barnacles begin as free-swimming larvae (nauplius and cypris stages). After settling, they metamorphose into sessile adults. They are common in intertidal and coastal zones worldwide, including all three Canadian coasts.

In short

  • Barnacles are crustaceans, not plants or shellfish.
  • They attach permanently using a natural cement.
  • They filter-feed with feathery cirri.
  • Common on hard surfaces in marine intertidal zones.
Canadian angle

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

Quick 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.

Sources

  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.