Article: On Placozoa - - The Simplest Known Animal

From: Robert Karl Stonjek (rstonjek_at_bigpond.net.au)
Date: 03/27/05

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    Date: Sun, 27 Mar 2005 17:34:19 -0500 (EST)

    EVOLUTION: ON PLACOZOA -- THE SIMPLEST KNOWN ANIMAL

    The following points are made by D.J. Miller and E.E. Ball (Current Biology
    2005 15:R26):

    1) Often described as the simplest known animal, the unassuming marine
    placozoan Trichoplax adhaerens is one of a handful of "lower" metazoans that
    have so far defied being pigeonholed. The history of Trichoplax and its
    relatives has the elements of a scientific mystery story [1]. In 1971, Karl
    Grell [2] formally described a new Phylum, the Placozoa, to accommodate two
    species that had been reported a hundred years earlier. These were
    originally greeted with excitement as "living fossils" representing the
    ancestral animal morphology. However, the suggestion that they were, in
    fact, modified cnidarian larvae prompted a loss of interest for the next
    fifty years. One of the species upon which Placozoa was founded, Treptoplax
    reptans, has never been seen since its original description, and is assumed
    not to exist; T. adhaerens, on the other hand, appears to be widely
    distributed and relatively common in warm marine environments [1]. However,
    other than field surveys [3], all that is known about it is based on
    aquarium cultures.

    2) ....

    Full Text at Science Week
    http://scienceweek.com/2005/sw050401-1.htm

    Posted by
    Robert Karl Stonjek

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