BACKGROUNDS: Gyrodactylus is a small monogenean ectoparasite that lives on the skin and fins of most of the world's fish species. Gyrodactylus appears to be one of the most prevalent parasites found in ornamental fish, especially in Cyprinids. Goldfish (Carassius auratus) are a popular ornamental fish that are highly contaminated by Gyrodcatylus. OBJECTIVES: The present study is aimed to identify morphological and molecular characteristics of the Gyrodactylus parasite on gold fish. METHODS: The morphological identification of Gyrodactylus specimens was performed using the measurements and drawings of opisthaptoral hard parts of the parasites. The molecular species description was based on a polymerase chain reaction (PCR) of partial sequence of the 5.8S region of ribosomal RNA, and a partial sequence of the internal transcribed spacer 2 (ITS2) of ribosomal RNA. The nucleotide sequences of the PCR products were compared with corresponding sequencing registered in GenBank. RESULTS: Based on the morphometric analysis and sequencing, the Gyrodactylus specimens were described as Gyrodactylus gurleyi. CONCLUSIONS: A combination of molecular techniques with morphological analysis seems to be the best approach for the identification of Gyrodactylus speices.
