Excystment in vitro of Cotylurus cornutus (Trematoda: Strigeidae) metacercariae

An acid-medium pretreatment appeared to be essential for in vitro excystation of Cotylurus cornutus metacercarial cysts. Both acid-pepsin or acid-saline were effective but optimum excystation occurred after 15 min acid-pepsin pretreatment and subsequent 2 hr treatment at 41.5 C in an alkaline bile salt-trypsin medium. The rate of excystation was rapid, reaching 78.1% by 1 hr and increasing to 84.3% after 2 hr. Storage of metacercarial cysts up to 16 wk at 4 C in sterile Locke's 1:1 solution did not alter cyst viability.