Ultrastructural characterisation and molecular taxonomic identification ofNosema granulosis n. sp., a transovarially transmitted feminising (TTF) microsporidium

A novel microsporidian parasite is described, which infects the crustacean host Gammarus duebeni. The parasite was transovarially transmitted and femi nised host offspring. The life cycle was monomorphic with three stages. Mer onts were found in host embryos, juveniles, and in the gonadal tissue of ad ults. Sporoblasts and spores were restricted to the gonad. Sporogony was di sporoblastic giving rise to paired sporoblasts, which then differentiated t o form spores. Spores were not found in regular groupings and there was no interfacial envelope. Spores were approximately 3.78 X 1.22 mu m and had a thin exospore wall, a short polar filament, and an unusual granular polarop last. All life cycle stages were diplokaryotic. A region from the parasite small subunit ribosomal RNA gene was amplified and sequenced. Phylogenetic analysis based on these data plates the parasite within the genus Nosema. W e have named the species Nosema granulosis based on the structure of the po laroplast.