Studies on the Development of Allassostoma parvum Stunkard

A little over a decade ago not a single life history was known for North American trematodes and up to the present time only ten, none of which concern amphistomes, have been experimentally established. An amphistome life history is here demonstrated through a study of larval and adult forms collected from the Ox-Bow, northeast of Urbana, Illinois. A cercaria from Planorbis trivolvis was found to encyst on crayfish and frog larvae, and when fed to bullfrogs (Rana catesbiana) and snapper turtles (Chelydra serpentina) developed into a known species, Allassostoma parvum Stunkard 1916. The extraordinary size of the terminal organs of the excretory system of the redia stimulated intensive studies on this system in both redia and cercaria stages. Sincere thanks and appreciation are here extended to Professor Henry B. Ward whose guidance and criticisms have made this work possible.