Phoronidea


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Phoronidea

 

a class of benthic marine invertebrates. The body, which measures 0.6–45 cm in length, is enclosed in a leathery chitinous tube. Numerous tentacles, located on the horseshoe-shaped base, surround the mouth. The Phoronidea feed on small organisms, moving them to the mouth with the cilia of the tentacles. The intestine is U-shaped. The anal opening is on the dorsal side, near the mouth. The nervous system has a dorsal “brain.” The secondary body cavity is represented by two (according to some research, three) pairs of coelomic sacs. The excretory organs are a pair of metanephridia. There is a circulatory system. The Phoronidea are dioecious. A planktonic larva, the actinotrocha, hatches from the egg.

The class comprises 23 species. Five species are found in the seas of the USSR. Some Phoronidea may possibly serve as food for benthic fishes. Phoronidea is usually classified in the phylum Tentaculata, but some systems assign it to the phylum Podaxonia. Still others view it as the independent phylum Phoronoidea.

REFERENCES

Livanov, N. A. “Foronidy, mshanki i brakhiopody.” Trudy ob-va estestvoispytatelei pri Kazanskom gos, un-te, 1963, vol. 66.
Zhizn’ zhivotnykh, vol.1. Moscow, 1968.
Dogel’, V. A. Zoologiia bespozvonochnykh, 6th ed. Moscow, 1975.