Fine structure and sporogonic development of a Vavraia sp. (Microsporida: Pleistophoridae) in the biting midge Culicoides edeni (Diptera: Ceratopogonidae)

A microsporidium with ultrastructural characteristics of the genus Vavraia was found in the fat body of an adult specimen of Culicoides edeni (Diptera: Ceratopogonidae) collected in northern Florida. The sporogonial stages developed within sporophorous vesicles, which contained variable numbers of oval spores at maturity. The wall of the sporophorous vesicle was composed of two electron-dense outer layers and an electron-lucent intermediate layer. Sporonts contained haplokaryotic nuclei and divided by rosette formation. Mature spores had anisofilar polar filaments and measured 3.8 +/- 0.28 microns in length and 2.2 +/- 0.16 microns in width in thick sections of resin-embedded material. This is the first report of a Vavraia sp. from a species of Culicodes.