A number of microscopic techniques and
dyes are available to diagnose microsporidian
infections in invertebrate and vertebrate hosts. Among these,
DNA-specific
fluorochrome DAPI is widely used to
stain DNA in prokaryotic and eukaryotic cells, alone or in combination with other histochemical or
fluorescent dyes. Moreover, this
dye also binds to membraneous structures and
protein complexes. In our studies,
DAPI was used to
stain spores of microsporidia infecting orthopteran, coleopteran, dipteran and lepidopteran insect hosts.
DAPI staining of diplokarya helped to discriminate the Nosema-like microsporidian spores from spore-shaped bodies lacking this characteristic staining. It was found, moreover, that non-
DNA staining occurred in many cases and other components of the spores were stained: the exospore, the cytoplasm, the extruded polar filament and the polaroplast. Staining of these structures was feeble as compared to
DNA and in most cases did not interfere with nuclear apparatus staining. Feebly stained cytoplasm and exospore clearly indicated unstained zone of endospore, making it easier to diagnose both mono- and diplokaryotic spores. Staining of extruded polar filament allowed to demonstrate viability and to observe some stages of extrusion process of microsporidian spores.