An adult Japanese eel that might have escaped from a dark sleeper’s stomach at some point in the past. Photo: Wikimedia Commons
Remember that scene in Alien where the Chestburster erupts out of Kane’s chest? It’s an iconic part of an iconic movie and generally thought of as nothing more than an awesome bit of science fiction. Japanese eels, however, are very much real, and they’ve taken a page from that scene.
“We have discovered a unique defensive tactic of juvenile Japanese eels using an X-ray video system,” said Yuuki Kawabata of Nagasaki University in Japan in a statement. They escape from the predator’s stomach by moving back up the digestive tract towards the gills after being captured by the predatory fish. This study is the first to observe the behavioral patterns and escape processes of prey within the digestive tract of predators.”
Japanese eels routinely become a meal for a fish with a decidedly evil-sounding name: dark sleepers. They’re not huge fish — about 10 inches long at most — but Japanese eels are only about five inches long, so they needed to figure out a way to evade getting digested.
The team of researchers watched in amazement as 32 eels were eaten by dark sleepers. Not all of them managed to fully escape, though. Thirteen came close, getting the ends of their tails out of the gills. Nine got all the way out and lived to fight another day. According to IFLScience, two of them tried to escape through an alternate exit, and not the exit that food goes in. They weren’t successful in their butt-route escape plan.
“The most surprising moment in this study was when we observed the first footage of eels escaping by going back up the digestive tract toward the gill of the predatory fish,” Kawabata says. “At the beginning of the experiment, we speculated that eels would escape directly from the predator’s mouth to the gill. However, contrary to our expectations, witnessing the eels’ desperate escape from the predator’s stomach to the gills was truly astonishing for us.”
The eels that were able to get all the way out of the dark sleepers did so pretty quickly, in an average time of just under a minute. The one that didn’t died in just over three minutes.
