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Marine Animal Encyclopedia

Horseshoe Worm Phoronis hippocrepia

Horseshoe worms are easily overlooked but they sometimes cover large areas of rock with their narrow, membranous tubes. The horseshoe worm lives inside its tube, which encrusts rock surfaces or can bore into shells or limestone rock so that only the top part of the tube shows. The end of the wormlike body is thickened and anchors the animal in its tube. The feeding head with its horseshoe of delicate ciliated tentacles is extended to catch tiny planktonic animals while the body remains hidden in the tube. The feeding head is called a lophophore and is found in all members of the phylum. Horseshoe worms brood their egg masses within the lophophore, and larvae are continually released to drift and develop in the water.

Horseshoe Wormzoom image
  • Phylum Phoronida
  • Length Up to 4 in (10 cm)
  • Depth 0–165 ft (0–50 m)
  • Habitat Rocks and empty shells
  • Distribution Shallow coastal waters of Atlantic Ocean, northeastern and western Pacific