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Strange Findings on Comb Jellies Uproot Animal Family Tree

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Unbelievably, comb jellies may have evolved separately from EVERY other animal!

So... completely unrelated to jellyfish?! Whoa.

"It's a paradox," said Leonid Moroz, a neurobiologist at the University of Florida in Gainesville and lead author of a paper in today's Natureabout the biology of the comb jelly nervous system. "These are animals with a complex nervous system, but they basically use a completely different chemical language" from every other animal. "You have to explain it one way or another."

The way Moroz explains it is with an evolutionary scenario—one that's at odds with traditional accounts of animal evolution.

Moroz and his colleagues have been studying comb jellies, whose scientific name is ctenophores (pronounced TEN-o-fors), for many years, beginning with the sequencing of the genome of one species,the Pacific sea gooseberry, in 2007. The sea gooseberry has 19,523 genes, about the same number as are found in the human genome.

The scientists enlarged their library to the genes of ten other species of comb jelly (out of the 150 or so species known to exist) and compared them to the analogous genes in other animals. And when they looked at the genes involved in the nervous system, they found that many considered essential for the development and function of neurons were simply missing in the comb jelly.

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