Acorn Worms and the Evolution of Gills

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The genomes of a pair of species of acorn worms have been sequenced. They're marine worms belonging to the phylum Hemichordata, and thus relatives of our distant ancestors.

"Acorn worm genome reveals gill origins of human pharynx" | Berkeley News

An adult female acorn worm, Saccoglossus kowalevskii, with eggs, collected near Woods Hole, Massachusetts. The series of parallel lines on the body below the orange collar are the pharyngeal slits used for filtering food from seawater. The gill slits were the origin of fish gills and the human pharynx. Image Credit: Chris Lowe, Stanford University

"It's an ugly beast," acknowledged John Gerhart, senior author of the report and a professor of the graduate school at UC Berkeley. "Acorn worms look very different from chordates, which makes it especially surprising that they and chordates, like humans, are so similar on the genomic, developmental and cell biological levels."

In fact, about 70 percent of human genes have counterparts in the acorn worms, suggesting that these are ancient genes inherited from the common ancestor.

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