Genome of simplest animal reveals ancient lineage, confounding array of complex ca...( Trichoplax was the earliest branch bef...)

"The latest and most complex analysis again suggests that placozoans populated the oceans long before sponges evolved," said Bernd Schierwater, director of the Institute of Animal Ecology & Cell Biology and head of the Center for Biodiversity at TiHo Hannover, Germany. Schierwater, a study co-author, joined Stephen Dellaporta and Leo Buss of Yale University in proposing the Trichoplax sequencing project in 2004 to DOE JGI's Community Sequencing Program [http://www.jgi.doe.gov/CSP/overview.html].

"The outcome of the Trichoplax adhaerens genome sequencing is so exciting that we are now culturing another 13 placozoan species in order to identify the most basal placozoan lineage and genome," said Schierwater.

"Trichoplax is an ancient lineagea good representation of the ancestral genome that is shedding light of the kinds of genes, the structures of genes, and even how these genes were arranged on the genome in the common ancestor 600 million years ago," said Srivastava. "It has retained a lot of primitive features relative to other living animals."

Originally collected from the Red Sea, and cultured over the last 40 years in the laboratory, Trichoplax is a two-millimeter flat disk containing fluid sandwiched between two cell layers. It lacks organs and only has four or five cell types. Yet, despite its apparent simplicity, its genome encodes a panoply of signaling genes and transcription factors usually associated with more complex animals.

Trichoplax has no neurons, but has many genes that are associated with neural function in more complex animals. "It lacks a nervous system, but it still is able to respond to environmental stimuli. "It has genes, such as ion channels and receptors, that we associate with neuronal functions, but no neu
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