Miracidium of Schistosoma mansoni: a macromolecular glycoconjugate as signal for the behaviour after contact with the snail host.

1. The behaviour of the miracidium of Schistosoma mansoni after contact with agar blocks containing Biomphalaria glabrata snail conditioned water (SCW) or its components, was studied. 2. "Repeated investigation" was the most specific response at contact with the snail host. 3. Fractionation and specific chemical treatment of SCW revealed that this response was stimulated by a lysozyme sensitive glycoconjugate with a mol. wt greater than 300,000. 4. Low molecular weight components of SCW had no stimulatory effect on the miracidia, although MgCl2 offered as pure chemical did so.