When Pacific hagfish burrow into a carcass and eat their way out, they may be feeding directly through their gills and skin as well as their guts.

Lab tests suggest that hagfish actively take up nutrients through their outer tissues, says fish physiologist Chris M. Wood of McMaster University in Hamilton, Canada. Plenty of marine animals without backbones can feed through their skin, but no one had demonstrated the power in a species so close to fish and modern vertebrates, Wood and his colleagues say in a paper to be published in the Proceedings of the Royal Society B.

“One of the i...