A crustacea has:
- An entire body divided into 3 parts; the head*, abdomen and thorax**.
- A hard exoskeleton.
- 2 pairs of antennae.
- The thorax bears legs, which may be specified as "walking legs"*** and "feeding legs"****.
- Produce Eggs
- 3 or 4 stages, depending of the animal
If you want to sound smarter, here are the more complicated words but have the same meanings.