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

Abstract

Thelohania parastaci sp. nov. infects the Australian freshwater crayfish, Cherax destructor. Data on morphology, developmental patterns and sequences from the small subunit (SSU) and internal transcribed spacer (ITS) regions of the ribosomal DNA (rDNA) of T. parastaci sp. nov. are described. The ultrastructural features of different life cycle stages are very similar to those of the European crayfish parasite Thelohania contejeani. T. parastaci sp. nov. exhibits simultaneous dimorphic sporogony in muscle tissue. Meronts, sporonts and spores are found in muscle tissue, within haemocytes in the hepatopancreas, and in the intestinal wall of infected crayfish. T. parastaci sp. nov. shows 92% sequence identity with T. contejeani and only 67% sequence identity with the fire ant pathogen T. solenopsae, when SSU rDNA sequences are compared. Analysis of SSU rDNA and ITS sequences of T. parastaci sp. nov. from crayfish from Victoria, Western Australia, and New South Wales indicate that the parasite has a wide geographical distribution in Australia.

Thelohania montirivulorum sp. nov. (Microspora: Thelohaniidae), a parasite of the Australian freshwater crayfish, Cherax destructor (Decapoda: Parastacidae): fine ultrastructure, molecular characteristics and phylogenetic relationships

“…The ultrastructural features of the episporontal space in SPVs were very similar to those described for T. parastaci (Moodie et al 2003) and T. contejeani (Lom et al 2001). Macrotubules (average diameter: 171 nm, n=60) and microtubules (average diameter: 85 nm, n=60) were evident in the cytoplasm external to the developing sporoblasts (Figs.…”

“…The SSU rDNA gene was 1,318-bp long, including the 18f and 1492r primers. This compared with 1,337 bp for T. parastaci (Moodie et al 2003) and 1,361 bp for T. contejeani c2 (Lom et al 2001). T. montirivulorum sp.…”

“…As yet, there are no internationally defined conventions to delimit species based on molecular criteria (Kunz 2002). Over 60 Thelohania species that are parasites of insects (Becnel and Andreadis 1999) and at least 9 species that are parasites of crustaceans have been described (Sprague 1950;Knell et al 1977;Lom et al 2001;Moodie et al 2003); SSU rDNA data was available for only 6 Thelohania species at the time of publication, 2 from fire ant hosts (Moser et al 1998), 3 from Trees were constructed using distance (A; GTR model), maximum parsimony (B) and maximum likelihood criteria (C; MrBayes maximum likelihood calculations). Bootstrap values >50% (10,000 repetitions) are indicated on the branches of trees A and B.…”

“…parastaci Moodie, 2002 is the first species of Thelohania to be described from an Australian crayfish host. It has been found in lowland populations of yabbies, including C. destructor albidus (Austin, 1996) from Western Australia and Victoria, and C. d. rotundus (Austin, 1996) from New South Wales (Austin 1996;Moodie et al 2003). T. parastaci is very similar to the European crayfish parasite, T. contejeani Henneguy, 1892, which infects Astacus fluviatilis L. (Henneguy and Thelohan, 1892).…”

“…T. parastaci is very similar to the European crayfish parasite, T. contejeani Henneguy, 1892, which infects Astacus fluviatilis L. (Henneguy and Thelohan, 1892). Moodie et al (2003) suggested a close relationship between the two species of Thelohania was indicated by features of their ultrastructure and development, and the relatively high sequence identity (92%) between the small subunit ribosomal DNA (SSU rDNA) sequences. The taxonomic affinities of T. contejeani have recently been reviewed in detail by Lom et al (2001).…”