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. 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.