Observations on the Fine Structure of the Nervous System of Echinococcus granulosus

Abstract

The fine structure of elements of the nervous systems of adults and protoscolices of Echinococcus granulosus is described. The lateral nerve trunks are composed of numerous unmyelinated fibers without a surrounding cellular sheath. The nerve fibers contain mitochondria and several sizes and types of vesicles. Synaptic junctions are commonly seen with clear vesicles accumulating on one side of the synapse. Dense vesicles resembling neurosecretory vesicles are seen at a presumed neuromuscular junction as well as in the nerve processes. A sensory ending in the tegument is described. This structure is composed of a ciliumlike terminal process, which extends beyond the tegumental surface from a bulbous expanded area. A rootlet structure is contained in the bulblike expansion. The rootlet is composed of filaments which emanate radially from the basal body and extend into the nerve process.