HOUSTON -- (Dec. 19, 2012) -- A new report in the journal Nature unveils three of the first genomes from a vast, understudied swath of the animal kingdom that includes as many as one-quarter of Earth's marine species. By publishing the genomes of a leech, an ocean-dwelling worm and a kind of sea snail creature called a limpet, scientists from Rice University, the University of California-Berkeley and the Department of Energy's Joint Genome Institute (JGI) have more than doubled the number of genomes from a diverse group of animals called lophotrochozoans (pronounced: LOH-foh-troh-coh-zoh-uhns).
Lophotrochozoans are a diverse group of animals that includes mollusks such as snails, clams and octopuses -- and annelids -- such as leeches and earthworms. Like humans and all other animals, lophotrochozoans can trace their evolutionary history to the earliest multicellular creatures. But the lophotrochozoan branch of the evolutionary tree diverged more than 500 million years ago from the branch that produced humans.
"Most animals, including people, have body plans with bilateral symmetry, which means they have left and right sides that are mirror images of one other," said co-author Nicholas Putnam, assistant professor of ecology and evolutionary biology at Rice. "When you look at all bilaterian species, you can divide them into three big groups that biologists call clades.
"Lophotrochozoans are one of these clades, and when we looked at all of the genomes that had been sequenced, we found that only two were lophotrochozoans," he said. "That left a big hole in the genetic record, and our goal with this study was to fill in some of the gaps in that blank space."
Genome sequencing for the new study was performed at JGI in Walnut Creek, Calif. The three newly sequenced species are Capitella teleta, an ocean-dwelling worm; Helobdella robusta, a freshwater leech; and Lottia gigantean, a large marine mollusk.
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