Evidence for an autonomic nervous system in decapod crustaceans

In vertebrates, the regulation of internal organs is primarily driven by the autonomic nervous system. In crustaceans, nervous control of organs has been investigated elaborately but primarily on the isolated organs. The increased interest in examining the whole system in crustaceans, especially in freely behaving animals, indicates that an ample and sophisticated nervous control of these internal organs is typical for these higher invertebrates. To prepare for rapid escape or confrontation, or for maintenance of a resting state during a relaxed period, these animals appear to need certain neural structures which can be compared to the autonomic nervous system of vertebrates. This review is to examine evidence for an analog to the autonomic nervous system in the crayfish and other decapod crustaceans. It was concluded that, notwithstanding obvious structural differences, some functional similarities take place in both groups of animals. The common features include the existence of its own nerve nets in the heart and digestive system as well as an inhibitory or acceleratory extrinsic control of their functions by specialized neurotransmitters. Additionally, the release of neuromodulators and neurohormones into the circulation appears to be widespread and extremely important for control of the vegetative organs in decapods as in vertebrates.