Crustaceans
- form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles.
- Crustacean's are the crabs, lobsters and woodlice. They breath through gills, so most of them live in wet places and many are aquatic.
The Respiratory System of Crustaceans
Many of the smaller crustaceans, such as the copepods, have no special respiratory organs. Gas exchange takes place through the entire thin integument. The inner wall of the carapace, facing the trunk, is often rich with blood vessels and may in many groups be the only respiratory organ. Gills, when present, are formed by modifications of parts of appendages, most often the epipodites. These thin-walled, lamellate structures are present on some or all of the thoracic appendages in cephalocarids, fairy shrimps, and many malacostracans.