Factors affecting surface changes in intact cercariae and cercarial bodies of Schistosoma mansoni

The effect of different incubation media and of temperature on the induction of water sensitivity has been investigated in intact and tailless Schistosoma mansoni cercariae. Removal of the cercarial tail by vortex stirring and elevation of the temperature of the medium from 27 to 37 degrees C resulted in the rapid onset of permeability changes in the larvae. The rate of change was greater in water than in TC-199 or Hanks' BSS media. Lowering the pH of the medium or increasing the concentration of Ca2+ ions decreased the rate of permeability change: raising the pH of the medium or the addition of 10(-5) M EDTA enhanced the rate. Raising the temperature of the medium also increased the rate of permeability change in intact cercariae although the rates obtained varied with the different media tested, being greatest in TC-199. It is concluded that both temperature elevation and loss of the cercarial tail influence the onset and rate of permeability changes in cercarial bodies during the transformation to schistosomula.