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SYNOPTIC DESCRIPTION OF THE PHYLUM PLACOZOA

SYNOPTIC DESCRIPTION OF THE PHYLUM PLACOZOA

EUKARYA>UNIKONTA>OPISTHOKONTA>ANIMALIA>PARAZOA>PLACOZOA
PHYLUM PLACOZOA LINKS

Description of Phylum

Hierarchical Classification

The following information came from Margulis and Schwartz (1998), Buchsbaum (1938), Barnes (1980), Barnes (1984a), Brusca and Brusca (2003), Hickman (1973), Nielsen (2001), Storer and Usinger (1965), and Tudge (2000).
  • I. SYNONYMS: Placozoa was defined by Grell in 1971. It has no common synonyms.
  • II. NUMBER: 1 or 2 known species.
  • III. PHYLUM CHARACTERISTICS:
    • A. Structure
      • Symmetry: None.
      • Body Cavity: Not present.
      • Body Covering: Upper surface covered by ciliated squamous epithelium (text with tooltip) Epithelium is a tissue that covers (or lines) a structure. Ciliated epithelium is made of epithelial cells that may have one or more flagella (=cilia) inserted into it. It is the chief means of locomotion for many invertebrates. ; lower surface covered by columnar ciliated epithelium.
      • Support: Hydrostatic (text with tooltip) A hydrostatic cavity is a fluid-filled cavity that provides support by muscular contraction of the surrounding tissue. by fluid-filled cavity.
      • Digestive System: Saprobic (Extracelluar, extracorporeal). Enzymes released from lower surface.
      • Circulatory System: None.
      • Locomotion: Movement by ventral ciliated epithelium. The ventral cells have a single flagellum with two orthogonal basal bodies (text with tooltip) Some flagellated taxa have motile cells with basal bodies that do not have attached flagella. Such basal bodies are called barren. The orientation of the basal bodies relative to each other can be varied. Orthogonal basal bodies occur at right angles to each other. (kinetosomes).
      • Excretory System: None.
      • Nervous System: None.
      • Endocrine System: None.
    • B. Reproduction:
      • Reproductive System: No special organs. Eggs and non-flagellated sperm are produced. Asexual reproduction (text with tooltip) As the name implies, asexual reproduction is the formation of offspring without the union of gametes. Usually, asexual reproduction involves the production of specialized cells or multicellular structures that can give rise to new individuals. occurs.
      • Development: Not known.
    • C. Ecology: Found mainly in marine aquaria.
LITERATURE CITED

Adl, S. M., A. G. B. Simpson, M. A. Farmer, R. A. Andersen, O. R. Anderson, J. R. Barta, S. S. Bowser, G. Brugerolle, R. A. Fensome, S. Fredericq, T. Y. James, S. Karpov, P. Kugrens, J. Krug, C. E. Lane, L. A. Lewis, J. Lodge, D. H. Lynn, D. G. Mann, R. M. McCourt, L. Mendoza, O. Moestrup, S. E. Mozley-Standridge, T. A. Nerad, C. A. Shearer, A. V. Smirnov, F. W. Spiegel, and M. F. J. R. Taylor. 2005. The new higher level classification of eukaryotes with emphasis on the taxonomy of protists. Journal of Eukaryotic Microbiology. 52(5):399-451.

Barnes, R. D. 1980. Invertebrate Zoology. Saunders College/Holt, Rinehart and Wilson, Philadelphia.

Barnes. R. S. K. 1984a. Kingdom Animalia. IN: R. S. K. Barnes, ed. A Synoptic Classification of Living Organisms. Sinauer Associates, Inc., Sunderland, MA. pp. 129-257.

Bergquist, P.R. 2001. The Porifera. In: Anderson, D.T., ed. Invertebrate Zoology. Oxford University Press. Oxford, UK. pp. 11-27.

Borchiellini, C., M. Manuel, E. Alivon, N. Boury-Esnault, J. Vacelet, and Y. Le Parco. 2001. Sponge paraphyly and the origin of Metazoa. J. Evol. Biol. 14: 171-179.

Brusca, R. C. and G. J. Brusca. 2003. Invertebrates. 2nd Edition. Sinauer Associates. Sunderland, MA.

Buchsbaum, R. 1938. Animals Without Backbones, An Introduction to the Invertebrates. The University of Chicago Press. Chicago.

Grell, K. G. 1971. Trichoplax adhaerens F. E. Schulze und die Entstehung der Metazoen. Natwiss. Rundsch. 24: 160–161.

Hickman, C. P. 1973. Biology of the Invertebrates. The C. V. Mosby Company. Saint Louis.

Margulis, L. and K. Schwartz. 1998. Five Kingdoms, an Illustrated Guide to the Phyla of Life on Earth. 3rd Edition. W. H. Freeman and Company. New York.

Ruppert, E. E., R. S. Fox, and R. D. Barnes. 2004. Invertebrate Zoology: A Functional Evolutionary Approach. Seventh Edition. Thomson, Brooks/Cole. New York. pp. 1-963.

Sperling, E.A., D. Pisani, and K.J. Peterson. 2007. Poriferan paraphyly and its implications for Precambrian palaeobiology. In: Vickers-Rich, P. and P. Komarower, eds. The Rise and Fall of the Ediacaran Biota. Geological Society, London, Special Publications. 286: 355-368.

Storer, T. I. and R. L. Usinger. 1965. General Zoology. 4th Edition. McGraw-Hill Book Company. New York.

Tudge, C. 2000. The Variety of Life, A Survey and a Celebration of all the Creatures That Have Ever Lived. Oxford University Press. New York.
By Jack R. Holt and Carlos A. Iudica. Last revised: 01/26/2010
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