Diurnal changes in the fine structure of photoreceptors in an abalone,Nordotis discus

Summary The ultrastructure of the synapses in the brain of the monogenean Gastrocotyle trachuri (Platyhelminthes) is described. The synapses consist of one presynaptic terminal separated by a uniformly wide synaptic cleft, from one or more postsynaptic elements. The presynaptic terminals are characterized by the presence of paramembranous dense projections and associated synaptic vesicles. The postsynaptic elements while possessing membrane densities, are usually devoid of vesicles.The structure of the synapses in the brain of Gastrocotyle is compared to synapses from other platyhelminths.