There is a saying that “do not let children lose on the starting line”, it seems that sharks have already known this: when their baby is in the mother’s stomach, they began to “practice” swimming.
Most mammalian fetuses are usually immobile in the mother’s womb, and the amplitude is not too large. Like mammals, some sharks are also viviparous, not oviparous. Scientists speculate that the shark fetus is always in one place. However, underwater ultrasonic display is not the case.
Recently, a Japanese research team performed an ultrasound scan of three pregnant rust sharks in an aquarium. The female rust shark has two connected uteruses, and the researchers found that the number of fetuses in both uterus has been changing since the third month of pregnancy.
This suggests that developing shark babies often swim from one uterus to another. To swim between the uterus, you must pass through a narrow U-shaped interface. Ultrasound images show that when the shark baby traverses the interface, it swings its tail, exactly the same as when the adult shark swims.
It is not clear why shark babies started swimming before they were born. One possibility is that they are looking for food. The fetus of the rust shark feeds on undeveloped eggs, and their swimming between the uterus may be to find more bad eggs.
If this is the case, the babies of the rust sharks are not consciously learning to swim “not losing on the starting line”, but to find food and learn to swim without knowing it.
The uterus is dark, how do they find the route? Researchers have speculated that shark babies may swim along the wall of the uterus and navigate by constantly touching the wall of the uterus.
