Molecular and structural assessment of microsporidia infecting daphnids: The "obtusa-like" microsporidia, a branch of the monophyletic Agglomeratidae clade, with the establishment of a new genus Conglomerata.

Microsporidia (Opisthosporidia, Microsporidia) are frequent parasites of planktonic cladocerans, including Daphnia (Crustacea, Branchiopoda). Analysis of available molecular data (ITS region and partial ssu and lsu rDNA) of these parasites indicates that many microsporidia infecting daphnids have a common ancestor and represent a large clade, which splits during evolution into a number of well supported subclades. These subclades are cytologically different but may be most conveniently characterised by their specific ITS barcode. We have analysed one of these subclades and we describe a new microsporidian genus and species combination, and assemble a large group of structurally indistinguishable microsporidian parasites that infect adipose cells of their hosts and form pyriform spores of a certain type ("obtuse spores"). Obtuse spores are non-infectious by feeding to their crustacean hosts and it is plausible that microsporidia forming them actually are parasites of insects with aquatic larval stages, with an obligate two-host life cycle, analogous to the Amblyospora life cycle involving copepods and mosquitoes.