A technique that could have been very useful in the case of the reticulated python, when it was swallowed by one of its fellows, a Burmese python.
Eels do not escape through the mouths of predators…
As The Guardian reports, these eels travel up the digestive tract of the predatory fish.towards its esophagus, push their tails into its gills and complete their attempt at freedom by releasing their heads”. A surprise for specialists, who thought they escaped through their mouths.
“Contrary to our expectations, seeing the eels desperately escaping from the predator's stomach towards the gills was truly astonishing for us,” Yuha Hasegawa, first author of the research from Nagasaki University, explained to the British media.
Divergent techniques
To conduct the experiment, the researchers used 104 Japanese eels. They then placed them in an aquarium containing a black sleeper fish, a species known for its voracity.
The scientists then injected barium sulfate into the abdominal cavity and tail of the eels, to track the progress of the ingested serpentine fish using X-rays. In total, 32 swallowed eels were recorded by the team.
Some of them circled in the stomach of the sleeping fish, looking for an exit. Two eels “took the wrong path” by heading towards the predator’s “genital orifice” rather than its esophagus. As for the others, they did try to extricate themselves from the fish via its gills. According to the study, this experiment “revealed that eels use multiple escape routes through gill slits, rather than just one”.
The only species capable of exiting the digestive tract of a fish
According to further examinations, this species of eel would be the only one capable of extricating itself from the digestive tract of its predator. At this point, the Japanese eel is the only fish species known to be able to escape from the digestive tract of predatory fish after being captured.” explained Yuuki Kawabata, another author of the study. We never imagined that eels could escape from the stomach of a predatory fish”, emphasized Yuha Hasegawa.
According to the scientist, the predatory fish are not injured when the eels are released. However, the eels show signs of abrasion. In the future, the researchers want to determine the specific factors involved in a successful escape for the eel.
Source: Current Biology
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