The Migration of Cotylurus erraticus Cercariae (Trematoda: Strigeidae) in Rainbow Trout (Salmo gairdneri) and Their Effects on the Host

The migration routes of C. erraticus cercariae were determined from laboratory infected rainbow trout which were killed at 12 intervals from 0-48 hours after exposureHistological sections were made, stained, and examined from these fish. The location and tissue were noted for each of 5,015 cercariae and the migration routes were determined from the progressive movement of cercariae in the tissues and organs. The circulatory system and loose connective tissue serve as migratory routes to the pericardium. The former is probably used by a greater percentage of the cercariae. The migration was nearly complete by 7.5 hours after exposure. Some cercariae were found in the body cavity after 48 hours. Hemorrhage was the primary effect of these cercariae on fish although a small amount of tissue damage was also found. THE MIGRATION OF COTYEURUS ERRATICUS CERCARIAE (TREMATODA: STRIGEIDAE) IN RAINBOW TROUT (SALMO GAIRDNERI) AND THEIR EFFECTS ON THE HOST by KEITH ALAN JOHNSON A thesis submitted to the Graduate Faculty in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in Zoology