PREVALENCE, TRANSMISSION AND INTENSITY OF INFECTION BY A MICROSPORIDIAN SEX-RATIO DISTORTER IN NATURAL GAMMARUS-DUEBENI POPULATIONS

This is a report of the prevalence, transmission and intensity of infe ction of a microsporidian sex ratio distorter in natural populations o f its crustacean host Gammarus duebeni. Prevalence in the adult host p opulation reflects differences in the intensity of infection in transo varially infected embryos and in adult gonadal tissue. The efficiency of transovarial parasite transmission to young also differs between po pulations, but this alone is insufficient to explain observed patterns of prevalence. Infection intensity may be important in determining fu ture infection of target tissue in the adult and subsequent transmissi on to future host generations. We consider patterns of parasite infect ion in terms of selection on transmission and virulence.