The neural commissural rings of the adult male Schistosoma mansoni.

Adult males of Schistosoma mansoni were preincubated in 5-hydroxytryptamine (5HT) and processed through the glyoxylic acid fluorescence technique to visualize 5HT-containing neural elements. 5HT fluorescence was seen as a series of cross-sectional rings beginning behind the ventral sucker toward the tail end. The rings were connected by two lateral nerve cords running longitudinally along the whole length of the worms.