Studies on the life cycle and transmission of Cougourdella sp., a microsporidian parasite of Glossosoma nigrior (trichoptera: Glossosomatidae)

Abstract

The trichopteran Glossosoma nigrior, the dominant benthic invertebrate grazer in Michigan trout streams, hosts a microsporidian (Protozoa) pathogen, Cougourdella sp., which strongly regulates the population density of larvae in the stream. In order to better understand the interactions between these two species, two possible modes of pathogen transmission, oral and transovum, were investigated. While both sexes of adult G. nigrior were found to be infected with mature environmental spores, spores were not found associated with reproductive tissue. This suggests that transovum transmission does not occur in this system. Glossosoma nigrior, when exposed to viable spores taken from infected larvae, did not produce Cougourdella sp. infections, which suggests that oral transmission also does not occur. It is possible that an intermediate host is required.