New diplokaryotic microsporidia (Phylum Microsporidia) from freshwater bryozoans (Bryozoa, Phylactolaemata)

Abstract

Three new species of microsporidia from freshwater bryozoans were investigated by microscopy and rDNA sequencing. These microsporidia and the previously described Nosema cristatellae have been ascribed to new genera, Pseudonosema gen. nov. for N. cristatellae from Cristatella mucedo, Trichonosema gen. nov. for Trichonosema pectinatellae sp. nov. from Pectinatella magnifica and Bryonosema gen. nov. for Bryonosema plumatellae sp. nov. from Plumatella nitens and for Bryonosema tuftyi sp. nov. from Plumatella sp. The new genera have been placed in a new family Pseudonosematidae with the following characters: diplokaryotic, disporoblastic and development in direct contact with host cell cytoplasm; spores of known species large with numerous polar tube coils; exospore dense with spiky extensions; or without spiky extensions and constructed of one or two layers; endospore and exospore thinned over the anchoring disc; anchoring disc ovoid with denser boundary around lucent interior penetrated by the inner core of the polar tube; polar sac small, umbrella-like; polar tube coils arranged as a single row anteriorly and posteriorly and as 2 or 3 rows in the middle; prominent reticulate Golgi system in sporoblasts and immature spores. Analysis of 16S rDNA by Baysian inference, maximum likelihood and parsimony placed all four species from bryozoans in one clade but the genera Trichonosema and Pseudonosema were separated from Bryonosema by the genera Janacekia and Bacillidium, which, on morphological grounds, cannot be included in the new family. The species are identified by morphological characters and their small subunit rDNA sequences.