Anatomy & Physiology

Digestive system
The decapods have a complete gut - ie: it enters and exits the body via different holes. In a typical decapod digestive system, the foregut and hindgut both have a cuticle, whereas the midgut does not. Food enters the esophagus, then travels to a 2-chambered stomach. Both chambers have a region for easily digested substances, and a region for substances that are harder to digest. The front stomach, known as the cardiac chamber uses a gastric mill to grind food, which is then easier to digest. The setal screen of the cardiac chamber filters small particles through to the next chamber, the pyloric chamber whilst stopping any large, indigestible particles, which are directed to the intestines and the rectum via the dorsal channel. The particles in the pyloric chamber enter the filter press, which has the gland filter that acts as another sieve to filter even smaller particles. These enter the midgut, which has extensively folded ceca, which secrete enzymes and absorb food particles (Ruppert et al., 2004).

Gas exchange and respiration
Decapods have 34 paris of gills enclosed in a gill chamber, where each gill is attached to a coxa. The gills exchange gases and ions to the surrounding water. Water enters an inhalent chamber via inhalent apertures, across the gills and to the exhalent chamber and out via exhalent apertures, which are relatively restricted in brachyurans and located in their chelipeds. The water is forced through by a gill bailer (Ruppert et al., 2004).

Internal transport - the hemal system
This system has a heart located in the thorax. Blood  is transported via an arterial system, capillaries and sinuses. The blood contains a pigment known as hemocyanin (which has a similar function to haemoglobin), and in many Portinuids accounts for most of the oxygen transport (Ruppert et al., 2004).