There are four kinds of horseshoe crabs in the world: American horseshoe crab, scorpion horseshoe crab, giant horseshoe crab and Chinese horseshoe crab (the second-class protected animal in China). The body surface is covered with chitin exoskeleton, which is brown. The head and chest have well-developed horseshoe-shaped carapace, which is often called horseshoe crab (but it has nothing to do with crabs). Male and female adults often live together, live in sandy shallow waters, and often crawl or sneak in the mud. Limulus first appeared in America, and then spread to Asia with the movement of the earth's plates.
brief introduction
The body is almost ladle-shaped, and it is divided into three parts: head, chest, abdomen and tail. It has no antennae, and its head and breastplate are broad and half-moon-shaped. There are 6 pairs of appendages on its ventral surface. The first pair of appendages are claw limbs, which are used for feeding. The epigastrium is small, slightly hexagonal, with several sharp spines on both sides, six pairs of flaky swimming limbs below, and a pair of gills on each of the last five pairs for breathing.
The tail is sword-shaped, slender and three-spindle-shaped, and it is articulated with the abdomen to support the body, especially when the back and abdomen are turned over. There are three longitudinal ridges faintly visible on the back of the nail. There are a pair of monocular eyes on both sides of the front end of the middle ridge and a compound eye on the outer side of the lateral ridge, in which the monocular eye can be used to sense light and the compound eye can be used to find the opposite sex.