Some will see it as a sequence worthy of a horror movie, others will admire the unlimited power of the animal survival instinct. The images made public on Monday, September 9, by a team from Nagasaki University (Japan), in support of an article published in the journal Current biology, can only impress. We see a young eel swallowed by a large fish, which emerges from the stomach and escapes from the predator’s body through… its gills.
Yuuki Kawabata and his colleagues carried out this observation in two stages. During an initial investigation, published in 2022, they wanted to study the behavior of juvenile Japanese eels in the face of one of their predators. In the role of the latter, the black sleeper (Dark odontobutis), a solid and unattractive cousin of the gobies. In contrast, the fragile eels, about a year old and fresh from their eel stage, did not exceed 7 centimeters. During their observation, they discovered, “stunned”One of the prey previously ingested – therefore, through the mouth – comes out this time through the gills. “We thought that eels went directly from the black sleeper’s mouth to these gills. We wanted to see exactly how.”says Yuuki Kawabata.
Observing the operation was not easy. There are X-ray cameras. They can see through the predator’s body. But the eels’ skeleton is so thin that it cannot be imaged. That’s why they were injected with a contrast agent, barium sulphate. They also had to adapt the aquariums to avoid unwanted movements of the predators and thus follow the entire operation on video.
And then, the second shock: they noticed that all the eels had been swallowed and that they had continued their journey down the black sleeper’s oesophagus until they reached the stomach. This is where the “survival” operation begins, the accumulation of strength and flexibility. The eel unfolds its thread-like body, starting with the tail, which moves backwards and slides towards the sphincter. From the stomach, it goes up the esophagus and deviates towards the gills. Once the end comes out, it grabs onto the edge, starts pulling the rest of the body. Finally the head turns, tilts and escapes from the trap.
Nine eels rescued
This behaviour seems all the more surprising as the stomach (of all species together) is known to be particularly hostile, even towards prey that has not yet been bitten. Between the extreme acidity and the lack of oxygen, survival time is limited. The Japanese researchers found that after 210 seconds, no movement was recorded because the eels succumbed. Those who survive this therefore act much more quickly. On average, fifty-six seconds.
You have 34.14% of this article left to read. The rest is reserved for subscribers.
