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Fingerlings of the sutchi catfish Pangasianodon hypophthalmus, a favorite food fish in South Asia, is regularly imported by European fish traders and sold in pet fish shops. In shipments from Thailand, a skin and a kidney infection of this fish caused by myxosporean parasites was found both in Hungary and Russia. In the skin of the fish, small millet-sized nodules containing great numbers of a Myxobolus species were found, while in the renal glomeruli, spores and sporogonic stages of a Hoferellus species developed. The skin-infecting species described as Myxobolus hakyi sp. n. had 15.9 x 6.6-microm-sized spores with elongated polar capsules, while the renal species described as Hoferellus pulvinatus sp. n. had roundish spores with a size of 6.5 x 5.0 microm and had a characteristic pillow-like structure at its posterior end. Besides morphology, histology of infection and 18S rDNA sequences were studied.

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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).