(Söderbäck 1992) may underpin the observed reduction in juvenile in P. leniusculus mixed populations. Parasitism in native and invasive crayfish Four species of microsporidia were detected in the invasive crayfish P. leniusculus. In contrast, only one microsporidian parasite was detected from although A. pallipes the sample size was The overall prevalence of microsporidian infection in P. was 38 % (Table 2). This prevalence is higher than previous reports of leniusculus visible microsporidiosis in in Britain (9 %, (Brown and Bowler 1977); 26 A. pallipes % (Rogers et al. 2003); 30 % (Evans and Edgerton 2002)), France (0-8%, Chartier and Chaisemartin 1983) and Spain (1%, Dieguez-Uribeondo et al. 1993), probably reflecting a higher detection efficiency by PCR. The sequences we obtained were identical to those previously T. contejeani isolated from (Genbank accession numbers AF492593 and Astacus fluviatilis AF492594, Lom et al. 2001). This is, to our knowledge, the first molecular confirmation of infecting as well as the first report of the T. contejeani P. leniusculus, parasite in an invasive species in Europe. Whilst has previously been T. contejeani reported from in the UK (Brown and Bowler 1977; Austropotamobius pallipes Edgerton et al. 2002; Rogers et al. 2003), these reports were based on light microscopy and lack the ultrastructural or molecular information to confirm species identity (Dunn and Smith 2001). This is the first molecular confirmation of the presence of infecting T. contejeani A. pallipes. The presence of in the invasive leads to the question T. contejeani P. leniusculus of how the parasite has come to infect this species. Firstly, may have P. leniusculus
(Söderbäck 1992) may underpin the observed reduction in juvenile P. leniusculus in mixed populations. Parasitism in native and invasive crayfish Four species of microsporidia were detected in the invasive crayfish P. leniusculus. In contrast, only one microsporidian parasite was detected from A. pallipes although the sample size was The overall prevalence of microsporidian infection in P. leniusculus was 38 % (Table 2). This prevalence is higher than previous reports of visible microsporidiosis in A. pallipes in Britain (9 %, (Brown and Bowler 1977); 26 % (Rogers et al. 2003); 30 % (Evans and Edgerton 2002)), France (0-8%, Chartier and Chaisemartin 1983) and Spain (1%, Dieguez-Uribeondo et al. 1993), probably reflecting a higher detection efficiency by PCR. The T. contejeani sequences we obtained were identical to those previously isolated from Astacus fluviatilis (Genbank accession numbers AF492593 and AF492594, Lom et al. 2001). This is, to our knowledge, the first molecular confirmation of T. contejeani infecting P. leniusculus, as well as the first report of the parasite in an invasive species in Europe. Whilst T. contejeani has previously been reported from Austropotamobius pallipes in the UK (Brown and Bowler 1977; Edgerton et al. 2002; Rogers et al. 2003), these reports were based on light microscopy and lack the ultrastructural or molecular information to confirm species identity (Dunn and Smith 2001). This is the first molecular confirmation of the presence of T. contejeani infecting A. pallipes. The presence of T. contejeani in the invasive P. leniusculus leads to the question of how the parasite has come to infect this species. Firstly, P. leniusculus may have
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