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A weird wee beastie: Trichoplax adhaerens - English
URL: http://www.microscopy-uk.org.uk/mag/artoct98/tricho.html

Trichoplax is an interesting organism to study, because it is one of those "missing links" that provides some hints about the evolution of some of the metazoa. It has only three cell layers and purportedly only four different kinds of cells. However, it raises interesting questions, some of which are still not completely answered. How it feeds is still something of a perplexity. It seems that it absorbs its nutrition through the ventral surface and probably feeds on algae.

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Trichoplax - Phylum Placozoa - English
URL: http://www.angelfire.com/mo2/animals1/phylum/trichoplax.html

General reference.

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Placozoa - English
URL: http://rainbow.ldeo.columbia.edu/ees/life/slides/oldec/placozoa.html

Only a single species, Trichoplax adhaerens, is known in this phylum. Like the other Parazoa, it lacks tissues, organs and organ systems, head and tail, and left and right. Soft bodied and inconspicuous, it is the simplest of animals. Trichoplax looks like a very large amoeba; it is barely visible to the naked eye. One can see under higher magnification that the "amoeba" is really an animal composed of a few thousand cells. Because most of the surface cells bear undulipodia (cilia), the entire surface of the animal is ciliated. Picture.

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PHYLUM PLACOZOA - The ‘plate’ animals - English
URL: http://www.teaching-biomed.man.ac.uk/bs1999/bs146/biodiversity/placoz.htm

This phylum is represented by a single described species known as Trichoplax adhaerens. However, this situation is surely farcical and numerous other species belonging to this phylum must be awaiting description. Trichoplax is a very small marine animal, 2 - 3 mm in length. It has no appreciable symmetry, no organs, no musculature and no nervous system to speak of. The body is composed of two plates of epidermal cells bearing cilia, which enclose a layer of loosely arranged cells.

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Placozoa: brief checklist - English
URL: http://erms.biol.soton.ac.uk/lists/brief/Placozoa.shtml

Part of European Register of Marine Species.

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Introduction to Placozoa - English
URL: http://www.ucmp.berkeley.edu/phyla/placozoa/placozoa.html

shown in filters: Guides et annuaires

Very little is known about them because they have never been observed in their natural habitat. No one knows what substrate they live on or what they eat in nature. It is even unknown whether or not they reproduce sexually like most animals. They were discovered in the late 1880's living on the glass walls of an aquarium in a European laboratory. Since then, most of what has been learned about their biology has come from studying cultures of them kept alive in various laboratories around the world. Not surprisingly, given their small size and squishy nature, fossil placozoans have yet to be discovered.

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