Analysis of the movements of Schistosoma mansoni miracida using dark-ground photography.

A dark-ground photographic technique was used to study the effects of several physical and chemical conditions on the behavior of Schistosoma mansoni miracidia. Miracidial speed was affected by miracidial aging, temperature, light intensity, and to a small extent by snail conditioned water (SCW). Rates of change of direction were influenced by miracidial aging, sudden increases in light intensity, and by SCW at 20%, 60%, and 100% concentrations. Adaptation to 20% SCW was apparent within 40 min of miracidial contact with the solution.