Thelohania contejeani Henneguy, 1892: dimorphic life cycle and taxonomic affinities, as indicated by ultrastructural and molecular study

Thelohania contejeani is a dimorphic species with two simultaneous routes f or sporogony. In the first, diplokaryotic sporonts produce 8 uninucleate sp ores with 9-10 turns of polar tube, within a sporophorous vesicle wall. The episporontal space contains two kinds of tubules and a spongiform mass. In the second, single diplokaryotic sporonts produce small membrane-bound com partments in which they transform into mature diplokaryotic spores with 5-6 turns of polar tube. Analysis of the small subunit (SSU) rRNA revealed two copies of 16S-like rDNA, one of them 1,311 bp, the other 1,361 bp long, wi th an overall identity of 93%. The majority of sequence differences were lo cated in a 120-bp stretch between positions 336 and 456, with only 40.5% id entity between the sequences. Careful consideration suggests that the short er sequence represents a pseudogene. According to the SSU rDNA sequence, T. contejeani is not closely related to any of the microsporidians where this sequence is available and could not be unambiguously placed in the 16S phy logenetic tree.