Biodiversity of monogenean parasites of fishes in Caspian Sea

Objective: Caspian Sea is an ancient lake which is being under many changes in its ecological conditions, resulting in a great diversity of its parasitic fauna. The aim of the present study is to investigate the biodiversity of monogenean parasites in Caspian Sea. Method & Materials: The data in the present study are from previous reports of monogeneans in Caspian Sea published by present authors and other investigators. Results & Conclusion: In total, 54 species of monogenean parasites belong to nine genera, including Dactylogyrus, Gyrodactylus, Ancyrocephalus, Ligophorus, Tetraonchus, Nitzschia, Diclibothrium, Mazocraes and Paradiplozoon, have been reported from 25 species of fish in the Caspian Sea. The dominant monogeneans are Dactylogyrus having 35 species, followed by the genus Gyrodactylus with 10 species. Ancyrocephalus and Ligophorus comprise two species each. The rest of the genera are represented by one species only. In recent years, the salinity of the Caspian Sea is being decreased gradually mainly due to connection between Volga River and Caspian Sea. The data shows that the composition of monogenean fauna in Caspian Sea is from both marine and freshwater origins. In addition, introduced fish species to Caspian Sea which belong to three families, including Mugillidae, therinidae and Pleuronectidae have their own specific monogeneans. Nitzschia sturionis may cause disease in marine conditions while some pathogenic species, i.e., Dactylogyrus vastator, D. extensus, Gyrodactylus katharineri and G. medius are specific to freshwater systems. Most of the species present had a boreal plain origin. Variation in morphology, host and origins of the various species are discussed here