Nervous system of Clonorchis sinensis as revealed by acetylcholinesterase activity.

The gross neuroanatomy of Clonorchis sinensis has been revealed by the localization of acetylcholinesterase, well known to be associated with the nervous system. The central nervous system is composed of two cerebral ganglia situated postero-dorsally to the pharynx and connected by a transverse commissure. These ganglia give off four pairs of nerves anteriorly and three pairs posteriorly. The anterior nerves contribute to the pharynx and to the formation of the circum-oral ring located in the oral sucker. The posterior nerves, of which the postero-ventral nerve cords are the most prominent, contribute to the innervation of the acetabulum, the gut, the reproductive organs and the excretory bladder. All the posterior nerve cords are connected by a number of transverse connections throughout their course forming a complicated nerve net. At least two types of nerve cells, bipolar and multipolar ones, were observed.