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

'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, 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.