Description and phylogeny of Zelenkaia trichopterae gen. et sp. nov. (Microsporidia), an aquatic microsporidian parasite of caddisflies (Trichoptera) forming spore doublets.

Two novel microsporidia infecting the fat body tissues in larvae of two hosts, Halesus digitatus and Micropterna sequax (Trichoptera, Limnephilidae), were investigated using light and electron microscopy and rDNA sequence analyses. The molecular and morphological characters of these isolates warrant creation of a new microsporidian genus, Zelenkaia gen. n., with two species, one named herein. Developmental stages of Zelenkaia spp. have single nuclei. In sporogony, a plasmodium with four nuclei gives rise by rosette-like budding to two pairs of uninucleate sporoblasts, each within a thin-walled, subpersistent sporophorous vesicle. Sporoblasts and mature spores adhere temporary together, forming doublets oriented in parallel, within the sporophorous vesicle. Spores are long-oval and uninucleate, and those of the type species Z. trichopterae measure 10.3×3.5µm and have 24-25 polar filament coils. Phylogenetic analysis based on rDNA places Zelenkaia spp. within the aquatic clade of microsporidia and, more specifically, in the clade containing some microporidia from amphipod hosts.