Placozoa – no longer a phylum of one

  title={Placozoa – no longer a phylum of one},
  author={Oliver Voigt and Allen Gilbert Collins and Vicki Buchsbaum Pearse and John S. Pearse and Andrea Ender and Heike Hadrys and Bernd Schierwater},
  journal={Current Biology},

Figures and Tables from this paper

The enigmatic Placozoa part 1: Exploring evolutionary controversies and poor ecological knowledge
The placozoan Trichoplax adhaerens offers unique prospects for understanding the minimal requirements of metazoan animal organization and their corresponding malfunctions.
Putting placozoans on the (phylogeographic) map
A world-wide collecting program greatly increases knowledge of the distribution of specific placozoan haplotypes, more than doubles the number of genetically characterized sites, and reports the first genetic data for isolates from the Eastern Atlantic and Indian Ocean.
Trichoplax and Placozoa: one of the crucial keys to understanding metazoan evolution
The discovery of Trichoplax adhaerens: In 1883, the German zoologist Franz Eilhard Schulze published a short communication on the description of a new species, Trichoplax adhaerens (the “sticky hairy
The Trichoplax genome and the nature of placozoans
Despite the apparent cellular and organismal simplicity of Trichoplax, its genome encodes a rich array of transcription factor and signalling pathway genes that are typically associated with diverse cell types and developmental processes in eumetazoans, motivating further searches for cryptic cellular complexity and/or as yet unobserved life history stages.
Morphological, evolutionary, internal and external phylogenetic aspects of the four phyla, including Porifera, Cnidaria, Placozoa and Ctenophora, are highlighted and discussed.
Comparative genomics and the nature of placozoan species
The multilevel comparative genomics approach is likely to prove valuable for species distinctions in other cryptic microscopic animal groups that lack diagnostic morphological characters, such as some nematodes, copepods, rotifers, or mites.
Global Diversity of the Placozoa
There is great potential and need to erect new taxa and to establish a firm system for this taxonomic tabula rasa within this phylum.
A taxogenomics approach uncovers a new genus in the phylum Placozoa
The genome of a placozoan lineage isolated from Hong Kong (lineage H13), which is distantly related to T. adhaerens, is sequenced and supports the designation of lineage HI3 as a new species and a robust placement of the Placozoa as sister to a cnidarian-bilaterian clade.
My favorite animal, Trichoplax adhaerens.
  • B. Schierwater
  • Biology
    BioEssays : news and reviews in molecular, cellular and developmental biology
  • 2005
The interest of zoologists and evolutionary biologists suddenly vanished for more than half a century when Trichoplax was claimed to be an aberrant hydrozoan planula larva and has been rediscovered as a key species for unraveling early metazoan evolution.


Placozoa are not derived cnidarians: evidence from molecular morphology.
The new molecular morphological characters provide compelling evidence that Trichoplax is not a derived (medusozoan) cnidarian, and it was found that the mitochondrial genome in Cubozoa consists of four linear molecules instead of a single circular molecule or two linear molecules, suggesting that the cubozoans may represent the most derived cNidarian group.
A new perspective on lower metazoan relationships from 18S rDNA sequences.
While sequencing additional lineages to identify slowly evolving taxa, the number of complete or nearly complete 18S rDNA sequences for the major diploblastic lineages was increased and the maximum-likelihood framework was used to choose a model which best explains the data.
Phylogeny of Choanozoa, Apusozoa, and Other Protozoa and Early Eukaryote Megaevolution
The taxon-rich rRNA phylogeny for eukaryotes allowing for intersite rate variation strongly supports the opisthokont clade and agrees with the view that Choanozoa are sisters of or ancestral to animals and reveals a novel nonflagellate choanozoan lineage, Ministeriida, sister either to choanoflagellates, traditionally considered animal ancestors, or to animals.
Phylogeny of Medusozoa and the evolution of cnidarian life cycles
To investigate the evolution of cnidarian life cycles, data from the small subunit of the ribosome are used and indicate that Cnidaria is monophyletic and composed of Anthozoa and Medusozoa.
Growth and Behavior of Trichoplax adhaerens: First Record of the Phylum Placozoa in Hawaii
The first record of Trichoplax adhaerens F. Schulze (phylum Placozoa) in Hawaii is reported and some observations on their behavior and growth rates in mixed laboratory culture are described.
Distinct expression patterns of the two T-box homologues Brachyury and Tbx2/3 in the placozoan Trichoplax adhaerens
It can be concluded that this simple animal has more than the four cell types described in the literature, and the unresolved position in relation to Porifera, Cnidaria, Ctenophora and Bilateria highlight the necessity of the inclusion of Trichoplax in studies of comparative evolutionary and developmental biology.
Homology of Hox genes and the zootype concept in early metazoan evolution.
Comparison of the Trox-2 gene from the presumably most basal metazoan animal, the placozoan Trichoplax adhaerens, to other Hox genes suggests the presence of unambiguous homologs in Hydrozoa and Scyphozoa and the absence of any specific homolog in triploblasts.
The Trox-2 Hox/ParaHox gene of Trichoplax (Placozoa) marks an epithelial boundary
The full coding region, spatial expression and function of Trox-2, the single Hox/ParaHox-type gene identified in Trichoplax adhaerens and either a candidate ProtoHox or a ParaHox gene is described.
Evaluating multiple alternative hypotheses for the origin of Bilateria: an analysis of 18S rRNA molecular evidence.
  • A. Collins
  • Biology
    Proceedings of the National Academy of Sciences of the United States of America
  • 1998
Six alternative hypotheses for the phylogenetic origin of Bilateria are evaluated by using complete 18S rRNA gene sequences for 52 taxa to suggest that there is little support for three of these hypotheses, but one is most strongly supported.
Global Dispersal of Free-Living Microbial Eukaryote Species
The abundance of individuals in microbial species is so large that dispersal is rarely (if ever) restricted by geographical barriers. This “ubiquitous” dispersal requires an alternative view of the