COMPARATIVE OBSERVATIONS ON CERCARIAE AND METACERCARIAE OF ECHINOSTOMA-TRIVOLVIS AND ECHINOPARYPHIUM SP

Comparative observations were made on cercariae of Echinoparyphium sp. from Physa gyrina in Charlie's pond, Stokes County, North Carolina an d cercariae of Echinostoma trivolvis from Helisoma trivolvis in Northa mpton County, Pennsylvania. The cercaria of Echinoparyphium sp. has 43 collar spines, lacks penetration and paraesophageal glands, and has a conical tail without fin folds. The cercaria of E. trivolvis has 37 c ollar spines, penetration and paraesophageal glands a finger-like proc ess at the tip of the tail and fin folds. The length of the cercarial body and tail of E. trivolvis was significantly greater than that of E chinoparyphium sp. Cercariae of both species encysted in Biomphalaria glabrata snails in single and concurrent infections. In concurrent inf ections with a single cercaria of each species, 2 encysted metacercari ae were adjacent to each other in the saccular kidney of the snail at 24 hr postinfection. The diameter of encysted metacercariae of E. triv olvis was significantly greater than that of Echinoparyphium sp. Echin oparyphium sp. metacercariae excysted at 39 C in an alkaline trypsin-b ile salts medium used previously to excyst E. trivolvis. The length of excysted metacercariae of E. trivolvis was significantly greater than that of Echinoparyphium sp.