How does a crustacean carapace protect the body and gills?

The crustacean carapace serves as a protective shield that often encloses the animal's trunk, including its limbs and respiratory organs.1

Regarding the protection of gills, the carapace plays a critical role in many groups, particularly in decapods. In these animals, the gills are situated within a branchial chamber located beneath the overhanging carapace. This arrangement provides a physical barrier that shields the delicate, thin-walled gill structures from external damage. Furthermore, this chamber facilitates the controlled movement of oxygenated water over the gills, which is essential for respiration.23

While the carapace is a widespread feature, it is important to note that its presence and function vary across different groups; for instance, it is absent in amphipods and isopods, and in some species where it is present, it may not cover the leg bases where gills are located.13