Eels’ escape shows ‘the fight for survival doesn’t end after being eaten,’ scientist says

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When you’re a predatory fish, sometimes the lunch you gobbled up doesn’t agree with you. Rather than accepting its fate, the still-living meal escapes your stomach and flees through the nearest orifice.

Dark sleeper fish (Odontobutis obscura) can gulp down young Japanese eels (Anguilla japonica) whole, but the swallowed eels can wriggle back up through the digestive tract and out of the stomach, swimming to freedom through the bigger fish’s gills, scientists recently discovered.

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Such a feat may be hard to imagine, but researchers recorded the daring eel escapes using an X-ray video system, describing their findings in a study published Monday in the journal Current Biology.

“Before capturing the first X-ray footage, we never imagined that eels could escape from the stomach of a predatory fish,” said lead study author Yuha Hasegawa, an assistant professor in the Graduate School of Fisheries and Environmental Sciences at Japan’s Nagasaki University. “Witnessing the eels’ desperate escape from the predator’s stomach to the gills was truly astonishing for us.”

A Japanese eel exhibits circling behavior along a predator's stomach wall in this X-ray video footage.

In general, it’s unclear what happens when a fish is swallowed whole by another fish, making this revelation “super surprising and informative,” said ichthyologist Kory Evans, an assistant professor of biosciences at Rice University in Houston.

“We do know that many fishes have a second set of jaws in