In vitro excystation of metacercariae of Microphallus turgidus under different physicochemical conditions.

This study examined the excystation of metacercarial cysts of Microphallus turgidus under varying conditions of temperature, NaCl concentration, and pH. Metacercarial cysts were dissected from abdominal muscle tissue of grass shrimp Palaemonetes pugio, and immediately incubated for 24 h under one of the following abiotic conditions: temperature (22, 26, 30, 34, 38, and 42 degrees C), NaCl concentrations (0.5, 0.6, 0.7, 0.8, and 0.9%), pH (2, 3, 4, 5, 6, 7, and 8), and percent excystation was recorded. The optimum in vitro excystation of metacercarial cysts occurred in 0.7% saline at 38 degrees C at pH 7; 92% of the cysts excysted under these conditions. Our results indicate that such a combination of extrinsic factors is provided by the definitive host for successful excystation of M. turgidus.