Studies on the surfaces of cercariae and schistosomula of Schistosoma mansoni

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Abstract
The physical nature of the cercarial surface has been observed by several workers to change during the penetration of the cercaria through the skin and its metamorphosis into the schistosomulum. Very little is known about the chemistry of this change. This paper reports the effects of the treatment of the surfaces of cercariae and schistosomula with various reagents as assessed by light microscopy. It was found that there were great differences in the stability of the surfaces of these parasitic forms. The schistosomular surface was stable to 0·2 m acetic acid, 5% calcium chloride and 8 m urea, whereas the cercarial surface was affected by these reagents. 8 m urea completely dissolved the cercarial surface, while it had little visible effect on that of the schistosomulum. This dissolution of the cercarial surface could be prevented by including small quantities of sodium or calcium chloride in the 8 m urea solution. A method has been developed to isolate pure preparations of cercarial and schistosomular surfaces. Hypotheses about the chemical changes in the surface during metamorphosis should be amenable to investigation using this method.