Studies on resistance in snails. 7. Evidence of interference with the defense reaction in Biomphalaria glabrata by trematode larvae.

Echinostoma lindoense sporocysts that develop from irradiated miracidia normally are destroyed by amebocyte capsules in the ventricle of Biomphalaria glabrata within 10 days postexposure. The survival period of these ventricular sporocysts was considerably longer in snails that also harbored normal sporocysts of E. lindoense, Paryphostomum segregatum, or Schistosoma mansoni. Protection of irradiated E. lindoense sporocysts by the same of different trematode species is presumed to be the result of an active process by which normal sporocysts interfere with capsule formation and protect themselves and other trematode larvae from encapsulation. Homologous protection was stronger than heterologous.