California Aquatic Invasive Species (AIS)
University of California
California Aquatic Invasive Species (AIS)

Invasive Seaweeds and Hull Fouling Species

Tube worms

Scientific Name

Hydroides spp. (H. elegans, & H. gracilis) - Visit ITIS for full scientific classification. 



  • Small, tube-dwelling, marine worms.
  • Attach to hard surfaces by forming long, thick, irregularly coiled, white calcareous (chalk-like) tubes.
  • When viewed under a microscope, body segments and feather-like tentacles can be seen.
  • Occur in subtidal and low intertidal areas.
  • Abundant in marinas, docks, and rocky environments with many hard surfaces.
  • Found on a variety of natural and man-made surfaces including: woody debris, shells of other animals, oyster reefs, rocky reefs, pier pilings, vessel hulls, intake lines, canals, etc. 
Invasion Pathways and Distribution
  • Spread by attaching to vessel hulls, from which larvae swim to settle on surfaces in marinas.
  • One species, Hydroides elegans, is originally described from Sydney, Australia.
  • The exact native origin is assumed to be somewhere in the Indo-Pacific.
  • The origin of a close relative, H. gracilis, is Pacific Grove, California.
  • Both are found worldwide, including all along the California coast.
  • See NEMESIS for a distribution map. 
Life History
  • Filter-feeders; use feather-like gill tentacles to capture particles in the water.
  • Reproduce sexually by releasing sperm and eggs into the water, where they unite to form swimming larvae
  • Hydroides elegans is a well-known, dominant fouling species with the potential to outcompete native species for space and food.
  • The chalky tubes form heavy crusts on boat hulls.
  • This fouling growth roughens the hull’s surface, creating friction or “drag” that slows sailboats and increases fuel consumption for powerboats.
  • Tolerant of copper in antifouling paint, and are very difficult to remove.
References and Useful Links

For references by category and links to other useful AIS sites see our LEARN MORE page.

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