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

. Oligonucleolides GsV4B, GdV4 and GtV4, complementary to sequences from Gyrodactylus Salaris, 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 us 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 werespotted 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 identifyingGyrodactylus species found on salmonid fish, but cannot be used to distinguishG. salaris andG. thymulli.