EXCYSTMENT OF CRYPTOCOTYLE LINGUA METACERCARIAE

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Abstract
The excystation of metacercariae of Cryptocotyle lingua Creplin 1825, was observed under a variety of chemical and physical conditions known to be a part of the in vivo environment. Excystment is mediated by the action of digestive enzymes, and in enhanced by treatment with carbon dioxide, bile salt and cysteine. A succession of enzyme solutions, viz., the same sequence as that met with in the host''s digestive tract, is required. Best results were obtained at 37 [degree]C by exposing the cysts to pepsin at a low pH, followed by trypsin digestion with surface-active and reducing agents at near neutrality. Under these conditions, 98.1% of the metacercariae were excysted within one hour. No single factor proved to be an absolute requirement, but the combined effect was to stimulate excystment within a biologically useful period of time.