Redescription of Gyrodactylus teuchis Lautraite, Blanc, Thiery, Daniel & Vigneulle, 1999 (Monogenea: Gyrodactylidae); a species identified by ribosomal RNA sequence.

Molecular and morphological features of Gyrodactylus specimens from Oncorhynchus mykiss, Salmo trutta and Salmo salar were examined. Sequences from variable region V4 of the small subunit ribosomal RNA gene and the ribosomal RNA internal transcribed spacers, produced by the FRS Marine Laboratory, revealed that these were not the same as other well-characterised Gyrodactylus that are common on European salmonids and were in fact a distinct species. Initial morphological examination of the opisthaptor indicated that this species very closely resembles G. salaris Malmberg, 1957. More detailed analysis revealed differences in the shape of the marginal hook sickle of these two species and thus Gyrodactylus teuchis Lautraite, Blanc, Thiery, Daniel & Vigneulle, 1999 was erected. Analysis of the ribosomal RNA gene or spacer sequences remains the most reliable method of identifying this species. This is believed to be the first record of a Gyrodactylus species identified first from molecular data and confirmed by morphological examination; previous molecular analyses had provided alternative methods for identifying species that had already been described using morphological characters.