Yuanmu for fish is a metaphor for people, meaning that the direction or method is not right, because it is impossible for people to find fish in the tree. But mangrove killifish break the rules, not only can swim freely in the water, but also "climb" trees, which is eye-opening.

The mangrove killifish, also known as the Huaxi killifish, is very colorful and only a few centimeters long. At present, it is only distributed in a few areas such as Africa and South America. It is a living fossil-like creature that existed in the age of dinosaurs. In arid and rainy Africa, mangrove medakas living in ponds, because the water in the ponds often dry up, are forced to evolve continuously and have a kind of ability to cope with the natural environment. When the water in the pond is about to dry up, the mangrove killifish will bury their eggs in the soil, and when the rainy season comes again, these eggs will grow again and start a new life. In addition, the seemingly insignificant mangrove killifish can temporarily change their physiological structure, and their respiratory organs can switch between water and land. Mature mangrove killifish can use their body to beat the water surface and use the rebound force to prey on cicadas, crickets and other insects on the trees. When they realize that the water in the pond is about to dry up, they will use this special skill of "carp jumping over the dragon gate" to find the logs hollowed out by insects, and collectively move to the rotten tree holes or branches, and start their interesting " hibernation". Scientists have found that the mangrove killifish in the tree hole are connected end to end, neatly arranged, and they stay for several months without eating or drinking, and their metabolism drops to a minimum.