What will happen if an animal is swallowed raw?
The seal said that this question is not funny.
In late September, in the waters near Ana cortese, Washington, a whale-watching naturalist took an unusual photo: a humpback whale was swallowing fish, and a bewildered seal was mixed in its mouth.
Fortunately, seals are not a big problem, because whales can’t swallow a seal. Large whales like humpback whales, despite their huge mouths, can "eat".（lunge feeding）Intake a lot of small fish and water at one time,But their throats are only the size of grapefruit, which is far from enough to swallow prey much bigger than small fish.
The reason for being swallowed by mistake is very simple. When whales open their mouths to prey on small fish or krill, seals often feed in the same water area. If the seals get too close at this time, they may be caught in the whale’s mouth by mistake. As a result, because the whales can’t swallow, they can only spit out the seals from their mouths by repeatedly opening and closing their mouths.
The fate of seals is good. Those who are really swallowed want to live, so they have to find another way out, such as being bitten by Odontobutis.(Odontobutis potamophila)Swallowed Japanese eel(Anguilla japonica).
The "Meeting" between Odontobutis sinensis and Anguilla japonica
Japanese eels have a complex life cycle, their eggs hatch in the ocean, and their larvae are called willow eels.（leptocephali）The shape is slender and almost transparent. These larvae drift westward through the northern equatorial current, and then reach the coastal areas of East Asia by the Kuroshio current. This process lasts about 110 to 160 days, and then the larvae will become glass eels.（glass eels）, gradually into the estuary and fresh water.
Glass eels. Image source: Joe Reynolds
When the glass eel enters the river, it will stay in fresh water for 5 to 10 years. When it enters the yellow eel stage, it gradually grows and adapts to different habitats, mainly feeding on shrimp, insects and small fish. With the change of river environment, eels will migrate to different areas, such as estuaries, lakes or the upper reaches of rivers; When eels mature, they will begin to migrate to the deep Pacific Ocean in autumn to complete the breeding task.
Eel. Image source: global seafood
Eels enter the ocean in the larval stage (glass eel and yellow eel stage). During this long journey, they will face survival challenges brought by various predators. One of them is Odontobutis sinensis, an East Asian freshwater fish.The prey is swallowed into the stomach together with the surrounding water mainly by fast sucking, which is especially effective for smaller organisms (such as Japanese eel larvae).
Odontobutis sinensis Image source: Wikipedia
This seems to be an end moment. For most prey, entering the predator’s stomach means inevitable death. However, this time, the story did not end as expected.
The survival rate of small eels is as high as 69%
In order to observe how small eels escape from the stomach of predators, and how eels can survive tenaciously and try to escape after being swallowed by Odontobutis sinensis, Japanese eel larvae raised in the laboratory were used in the experiment. The average length of these eels was 68.1 6.0 mm (n = 104), and that of Odontobutis sinensis, a predator, was 145.4 15.6 mm (n =
The research team willBarium sulfate injectionThe Japanese eel larvae raised in the laboratory can be clearly captured by X-rays, and then the eel is put into the experimental water tank together with the "predator" Shatangyu, and the story begins.
Under X-ray, scientists found that the swallowed eels did not wait for death. They began to act in reverse, trying to swim back from the predator’s esophagus and looking for an exit. And at this time,Eels show their unique ability to escape: they can pass through the esophagus, put their tails into the gills of predators and gradually withdraw from the gills.
The swallowed eel has a tail in the white circle and a head in the black circle. Image source: references[1]
In the experiment, 32 eels were swallowed by predators, among which 13 eels successfully put their tails out of the gills, and 9 eels completed the whole escape process. This process is full of thrills and struggles, like an ultimate life-and-death competition.For those eels that successfully stick their tails out of their gills, their survival rate is as high as 69%.
The gills of Odontobutis sinensis were drilled from the tail of eel. Image source: references[1]
Scientists marvel at the complexity of this anti-predation strategy. They found that some eels move in a circle along the stomach wall after completely entering the stomach of predators, as if they were looking for potential escape paths everywhere.The secret of escape may lie in the body structure and swallowing order of eels.Snakeheads usually swallow their prey head forward, and eels’ tails are often left near the esophagus, which gives them a chance to escape first.
X-ray images and schematic diagrams. Figure B: The eel tail has been inserted into the predator’s esophagus, and the X-ray image clearly shows the position of the eel in the predator’s digestive tract. C: The eel tail begins to pass through the gill slits of predators, which is very important. Figure D: The eel pulls its head out of the predator’s gill, which indicates that the escape process is about to be completed. E: Eels swim around the stomach, showing an "exploratory" behavior, looking for possible escape paths. Image source: references[1]
Not only that,The experiment also revealed that eels need to respond as soon as possible in acidic and anoxic stomach environment.Once an eel enters a predator’s stomach, it can only live for about 211.9 seconds on average. Time is running out, and the boundary between life and death can often be decided in a few minutes.
Eels still have to struggle to find a way out, and for "fart bugs", being eaten by toads only needs to fart.
Yefart beetle "spits fire" in the stomach.
Similar to the above experiment (without X-ray), the object of this experiment is the beetle.(Pheropsophus kimaniae）。Once the beetle is swallowed by the toad, it won’t wait for its fate quietly, but it will launch a wonderful self-rescue operation:Yefart beetleIt will release a high-temperature chemical spray, which can not only protect itself, but also make toad feel severe discomfort.
Yeah, it’s a fart. Image source: Wikipedia
With a faint explosion, toad realized that he had made a mistake. In the next few minutes, toad tried to endure the stimulation of his stomach and had to make a shocking choice-vomiting.
Toad. Image source: references[2]
The success rate of the "fart bug" escape from life and death is not completely random. The study found that,The bigger the beetle is, the more chemicals it releases, and the higher the chance of escape.For toads, the smaller they are, the lower their chemical tolerance, so they are more likely to spit out beetles.
It can be said that this is a contest between "big" and "small": the little toad can’t bear the chemical counterattack of the beetle, while the big beetle has a greater chance to escape calmly. Finally, if you are eaten, don’t panic, there will always be a way out, provided that you are completely swallowed raw …
[1]Hasegawa Y, Mine K, Hirasaka K, et al. How Japanese eels escape from the stomach of a predatory fish[J]. Current Biology, 2024, 34(17): R812-R813.
[2]Sugiura S, Sato T. Successful escape of bombardier beetles from predator digestive systems[J]. Biology Letters, 2018, 14(2): 20170647.?
