Sequence analysis of the ribosomal internal transcribed spacer DNA of the crayfish parasite Psorospermium haeckeli

Two morphotypes of the crayfish parasite Psorospermium haeckeli were isolat ed from 2 crayfish species of different geographical origin. The oval-shape d sporocysts were obtained from the epidermal and connective tissue beneath the carapace of the noble crayfish Astacus astacus from Sweden and Finland . Elongated spores were isolated from the abdominal muscle tissue of the re d swamp crayfish Procambarus clarkii from USA. To compare genetic divergenc e of 2 morphotypes of the parasite, the ribosomal internal transcribed spac er (ITS) DNA (ITS 1 and ITS 2) and the 5.8S rRNA gene were cloned and seque nced. The analysed region is variable in length, with the ribosomal ITS seq uence of the European morphotype longer than the North American one, Sequen ce diversity is found mainly in ITS 1 and ITS 2 regions, and there is 66 % and 58 % similarity between the 2 morphotypes, respectively. Thus, analysis of the ribosomal ITS DNA suggests that P. haeckeli forms obtained from Eur ope and North America are genetically diverse, which supports the previousl y reported morphological characteristics.