Identification of Gyrodactylus (Monogenea) species parasitizing salmonid fish using DNA probes

Oligonucleotides GsV4B, GdV4 and GtV4, complementary to sequences from Gyrodactylus safaris, G. derjavini and G. truttae, respectively, were designed following examination of the sequence of the small subunit ribosomal RNA (srRNA) gene from each species. The oligonucleotides were end-labelled with digoxigenin for use as species-specific probes. The V4 region of the srRNA gene was amplified from individual gyrodactylids using the polymerase chain reaction (PCR) and aliquots of the PCR products were spotted onto nylon membrane. Optimum conditions for hybridization of the oligonucleotide probes to these samples were determined. The use of these three probes against aliquots of PCR product provides an objective, sensitive and specific method suitable for routine diagnostic use in identifying Gyrodactylus species found on salmonid fish, but cannot be used to distinguish G, safaris and G. thymalli.