| The purpose of this study was to determine the duration of infection by M. salvelini during the period after O. nerka enters sea water. An additional experiment was done to determine if a blood stage of M. salvelini existed and whether this stage could be transmitted by intraperitoneal injection of blood from infected smolts into uninfected smolts. O. nerka smolts were divided into two groups: fresh water and sea water. After 12 weeks, or the last detection of spores in the seawater fish, they were reacclimated to fresh water, left for 8 weeks, and re-examined for the presence of spores and developmental stages of M. salvelini in the kidney. After reacclimation to fresh water, M. salvelini resumed development and spore production, indicating that infection of M. salvelini persisted in an arrested stage during the seawater phase. This suggests that M. salvelini could persist within the kidney tubules for the seawater life of O. nerka, giving M. salvelini renewed status as a potential biological tag. All attempts at blood transmission of M. salvelini failed, but this does not rule out the possibility of the presence of a blood stage. (Abstract shortened by UMI.)... |
