Horseshoe crab is an animal that lives in the deep sea. It does not belong to fish, but belongs to Arthropoda and Arthropoda. Horseshoe crab is the largest arthropod. Some people call it horseshoe crab or horseshoe crab because it is shaped like a horseshoe and moves like a spider. At the end of Devonian 400 million years ago, horseshoe crab appeared, which can be called an ancient attached organism in the ocean. This is an animal as old as the fossil trilobite. It is called "living fossil" because it has not evolved much after vicissitudes of life and still maintains its original appearance.

Most horseshoe crabs in the water are in pairs; Because the female horseshoe crab has four pliers on its first four legs, while the male horseshoe crab has four hooks. It turns out that the male horseshoe crab always puts the hook on the back of the female shark so that the "wife" can carry it around to make a living.

The ugly and lazy horseshoe crab is single-minded about "love" Once a man and a woman get married, they are inseparable. The fat female horseshoe crab, with a smaller "husband" on her back, hobbles and crawls, thus gaining the reputation of "Yuanyang under the sea". Fishermen in Beibu Gulf call them "two in-laws". Every spring, deep water heats up, and groups of horseshoe crabs swim from the bottom of the sea to the beach to give birth. Experienced fishermen are familiar with the action route of horseshoe crabs and laid long fishing nets halfway in advance. Once the horseshoe crab is ambushed, it will die in the net. These couples, whether they swim from the deep sea to the shallow water or are taken to the "prison", have always stayed together and never separated. The most surprising thing is that when the male horseshoe crab was caught by his tail, the male horseshoe crab hugged the female horseshoe crab tightly, but the female horseshoe crab did not abandon her husband. As a result, they were carried out of the water together