The nuclear rDNA region of Gyrodactylus arcuatus and G-branchicus (Monogenea : Gyrodactylidae)

The primary structure of the ribosomal DNA internal transcribed spacers (IT S-1 and ITS-2) and 5.8S rRNA gene were used to characterize and identify 2 monogenean species of Gyrodactylus living externally on the threespine stic kleback (Gasterosteus aculeatus). The ITS region was amplified by PCR from freshwater, brackish, and marine isolates of Gyrodactylus arcuatus and G. b ranchicus, and the ends of the coding regions were identified by comparativ e alignment. No intraspecific and very low interspecific variation were obs erved in the 5.8S rRNA gene; high inter- and low intraspecific variation we re revealed in the ITS-1 and ITS-2 regions. The morphological species ident ification was in all cases confirmed by the molecular identification. Intra specifically, samples from 2 locations in the North Sea could be differenti ated, but the Baltic sample resembled North Sea genotypes. Our approach off ers perspectives for a multimetric genetical, morphometrical, and ecologica l taxonomy of the genus Gyrodactylus.