Amputated animals are characterized by exoskeleton, body and appendages. Crabs are arthropods, and their appendages are segmented, but why not segment them?

Arthropods are also called arthropods. Arthropods are called arthropods because they usually have a pair of segmented appendages on each body segment, which is also called arthropods. Therefore, the original definition of arthropod is the division of appendage, not the division of trunk.

There are many kinds of arthropods, some of which are undifferentiated in the chest and abdomen, and some of which are completely healed without splitting in the chest and abdomen. Some are split and trunk; Some are divided into three parts: chest and abdomen; Some are divided into chest (precursor) and abdomen (afterbody). Some somites have merged during embryonic development. Crab is a kind of inseparable chest and abdomen.