Life cycle, ultrastructure, and molecular phylogeny of Crispospora chironomi g.n. sp.n. (Microsporidia: Terresporidia), a parasite of Chironomus plumosus L. (Diptera: Chironomidae)

The life cycle, ultrastructure, and molecular phylogeny of a new microsporidium Crispospora chironomi g.n. sp.n., a parasite of the midge Chironomus plumosus, are described. The parasite infects the gut epithelium of the host larvae and possesses sporogonies of two types, polysporoblastic and disporoblastic, respectively, proceeding within the same host cell. In the sporogonial sequence of the first type, dozens of spherical monokaryotic spores within a thick-walled capsule are formed. The spores are 1.5–2.0 μm in diameter; the exospore possesses two to three bundles of tubular protrusions. In the sporogonial sequence of the second type, diplokaryotic oval spores, 2.5 × 1.5 μm in size, are formed within a compartment, partially surrounded with multilayered membranes. Spores of both types are similar in respect to inner structure, possessing a well-developed extrusion apparatus with (a) the anterior vesicular part of the polaroplast covering the lamellar posterior one and (b) isofilar polar filament with several coils in one row. Small subunit ribosomal DNA phylogeny showed position of the new microsporidium in a cluster uniting microsporidia of terrestrial origin infecting diverse hosts, nested within Clade IV, corresponding to Class Terresporidia sensu Vossbrinck and Debrunner-Vossbrinck (Folia Parasitol 52:131–142, 2005).