Acorn Worm (species: Balanoglossus sp.) in taxonomy (Lizard Island Field Guide)
Balanoglossus sp.
Acorn Worm

©Anne Hoggett: Distinctive sand mound made by a burrowing Acorn Worm (genus Balanoglossus); intertidal sand flat at Casuarina Beach, Lizard Island.

©Anne Hoggett: Numerous sand mounds made by Balanoglossus sp., a large burrowing Acorn Worm; intertidal sand flat at Casuarina Beach, Lizard Island.
Kingdom Animalia
Phylum Hemichordata
Class Enteropneusta
Family Ptychoderidae
Genus Balanoglossus
Species Balanoglossus sp.

Distinguishing features

Distinctive coiled piles of sand in the intertidal zone indicate the presence of buried acorn worms. The mounds are fecal casts, passed through the digestive tract of the deposit-feeding worms. Gibbs (1978) found three species of acorn worms (all in genus Balanoglossus) in the intertidal of islands not far to the south of Lizard Island.


  • Size data has not been obtained.



The volume of sand turned over each tide indicates that these worms play an important role in the ecology of intertidal sand flats.

by Anne Hoggett


Local abundance

  • Lizard Island: Extremely common on sandy intertidal areas

Web resources


References that assist with identification

  • Allen, G.R. and R. Steene (1994). Indo-Pacific Coral Reef Field Guide Tropical Reef Research, Singapore. ISBN: 981-00-5687-7.

Other references

  • Gibbs, P.E. (1978). Macrofauna of the intertidal sand flats on Low Wooded Islands, Northern Great Barrier Reef, Philosophical Transactions of the Royal Society B, 284: 81-97. LIRS catalog number 90199.