1. horseshoe crab is a kind of marine animal, which belongs to national protected wild animals and cannot be bought or sold. It is different from other animals. Its blood is blue because it contains copper ions, belongs to arthropods, and breathes through gills.

2. horseshoe crab, horseshoe crab, is an animal as old as trilobites. The blood of horseshoe crab contains copper ions, and the blood is blue. Marine horseshoe crabs, arthropods, arthropods. Sea horseshoe crab is an arthropod that breathes through gills. There are only four kinds in the world: Chinese horseshoe crab, American horseshoe crab, Malay horseshoe crab and round-tailed horseshoe crab.