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Phoronids: Phoronida

No Common Name (phoronis Ijimai): Species Account

Physical characteristics: Fully stretched out, these flesh-colored or clear-bodied phoronids may reach a length of 5 inches (120 millimeters) and are 0.02 to 0.08 inches (0.5 to 2 millimeters) thick. The lophophore sometimes is clear and has white spots. The lophophore is horseshoe-shaped, or coiled with a single spiral, and has as many as 230 tentacles. Each tentacle is 0.08 to 0.2 inches (2 to 5 millimeters) long.

Geographic range: This species is found in the eastern and western Pacific Ocean and the northwestern Atlantic Ocean.

Habitat: This species lives along coastlines, in zones affected by tides down to depths of approximately 33 feet (10 meters). They are found in groups of intertwined tubes covering rocks, wood, and other hard surfaces. They sometimes burrow in rock, algae, coral, and the shells of mollusks (mussels, clams, snails, and their relatives).

Diet: They capture plankton with their sticky tentacles.

Fully stretched out, these flesh-colored or clear-bodied phoronids may reach a length of 5 inches (120 millimeters). (Illustration by Bruce Worden. Reproduced by permission.)

Behavior and reproduction: They protect themselves by quickly withdrawing inside their tubes. Injured animals can replace damaged or lost body parts in just a few days.

This species has both male and female reproductive organs. The fertilized eggs are brooded in two groups on the tentacles. Fully grown larvae are approximately 0.03 inches (0.8 millimeters) long. Adults also reproduce by dividing their bodies in two.

Phoronis ijimai and people: This species is not known to impact people or their activities.

Conservation status: Phoronis ijimai is not considered threatened or endangered. ∎



Emig, C. C. "The Biology of Phoronida." Advances in Marine Biology (1982): 1-89.

Garey, J. R., and A. Schmidt-Rhaesa. "The essential role of "minor" phyla in molecular studies of animal evolution." American Zoologist 38, no. 6 (December): 907-917.

Web sites:

Introduction to the Phoronida. http://www.ucmp.berkeley.edu/brachiopoda/phoronida.html (accessed on March 28, 2005).

Phoronid@2005. http://www.com.univ-mrs.fr/DIMAR/Phoro/ (accessed on March 28, 2005).

"Phoronida. Horseshoe Worms." http://www.angelfire.com/mo2/animals1/phylum/phoronida.html (accessed on March 28, 2005).

"The Phoronida." http://www.ldeo.columbia.edu/edu/dees/ees/life/slides/phyla/phoronida.html (accessed on March 28, 2005).

Additional topics

Animal Life ResourceMollusks, Crustaceans, and Related SpeciesPhoronids: Phoronida - Physical Characteristics, Habitat, Behavior And Reproduction, No Common Name (phoronis Ijimai): Species Account - GEOGRAPHIC RANGE, DIET, PHORONIDS AND PEOPLE, CONSERVATION STATUS