Genetic characterization of six species of diplozoids (Monogenea; Diplozoidae)

The second internal transcribed spacer (ITS2) of the ribosomal RNA gene arr ay of 6 species of diplozoids; Eudiplozoon nipponicum, Paradiplozoon blicca e, P. homoion, P. megan, P. pavlovskii and P. sapae, was amplified by PCR a nd sequenced. These sequences clearly demonstrate discrimination at the spe cies level and confirm the validity of species determined by morphological identification. No intraspecific variation was found in the ITS2 sequences. There were no differences in the ITS2 sequences of P. homoion from populat ions parasitizing different host species. The length of the PCR product all owed discrimination of E. nipponicum from the Paradiplozoon species. Digest ion of the amplified ITS2 fragment with enzymes AluI, HaeIII and HinfI prov ided useful genetic markers for species identification. The genetic relatio nships between diplozoids again demonstrated that E. nipponicum was the mos t genetically distinct species, whereas P. bliccae and P. sapae were the sp ecies most closely related. This represents the first molecular taxonomic s tudy of these interesting parasites and demonstrates the utility of these m ethods for addressing questions of systematics.