Schematic drawing of the stomatogastric nervous system (STNS) of Jonah crab, Cancer borealis. The SGs (sinus glands: located in the eyestalks of the crab) and the POs (pericardial organs: located in the chamber surrounding the heart) release hormones into hemolymph. The brain is connected to the STNS via a tiny nerve called the inferior ventricular nerve (ivn), and the STNS consists of the stomatogastric ganglion (STG), oesophageal ganglion (OG), paired commissural ganglia (CoGs), which connected by motor nerves.