In DepthEvolution

Comb jelly ‘anus’ guts ideas on origin of through-gut

Science  25 Mar 2016:
Vol. 351, Issue 6280, pp. 1378-1380
DOI: 10.1126/science.351.6280.1378

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Summary

Several unprecedented videos of gelatinous sea creatures called comb jellies, or ctenophores, now threaten to upend the standard view of the evolution of the so-called through-gut. Comb jellies, jellyfish, sea sponges, and a few other creatures all were thought to lack an anus, which meant they had to eat and defecate through a single hole. These are descendants of some of the first animals to arise, so it has been thought that the through-gut and anus were an innovation that came after those lineages emerged—and perhaps something that drove the diversity of new animal forms. But on 15 March, at the Ctenopolooza meeting in St. Augustine, Florida, evolutionary biologist William Browne of the University of Miami in Florida debuted films of comb jellies pooping—and it wasn't through their mouths. Browne's videos elicited gasps from the audience, who is now rethinking when the through-gut first evolved—and whether it may have emerged more than once.

  • * Amy Maxmen is a writer based in Berkeley, California.