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

Abstract

Thelohania contejeani is a dimorphic species with two simultaneous routes for sporogony. In the first, diplokaryotic sporonts produce 8 uninucleate spores 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 compartments 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, with an overall identity of 93%. The majority of sequence differences were located in a 120-bp stretch between positions 336 and 456, with only 40.5% identity between the sequences. Careful consideration suggests that the shorter 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 phylogenetic tree.

Description of microsporidia in simulids: molecular and morphological characterization of microsporidia in the larvae of Simulium pertinax Kollar (Diptera: Simuliidae)

“…This identifi cation corroborated previous results [22][23][24][25][26] regarding the phylogeny of these parasites.…”

Histological analysis of thelohaniasis in white-clawed crayfishAustropotamobius pallipescomplex

“…The observed histological lesions were similar to those described in A. pallipes by Cossins and Bowler (1974) and in A. astacus by Oidtmann et al (1996), where up to 90% of the muscular fibres were infected. Concerning the results observed by transmission microscopy, the spores were usually found free and a few were inside a sporophorous vesicle as has already been observed by Lom et al (2001). Indigenous European crayfish species, such as A. pallipes complex, now live within a considerably restricted geographical area, largely due to disease, pollution, destruction of habitat and stressed water.…”

Thelohania parastaci sp. nov. (Microspora: Thelohaniidae), a parasite of the Australian freshwater crayfish, Cherax destructor (Decapoda: Parastacidae)

“…Only uninucleate spores developed within SPVs. Characteristic microtubules and fibrous macrotubules, similar to those of T. contejeani (Lom et al 2001), were found in the episporontal spaces of SPVs (Figs. 16,17).…”