Monogenean Infestations Among Freshwater Ornamental Fishes: An Overview

Diseases outbreaks are being increasingly recognized as a significant constraint to aquaculture and ornamental fish trade and affecting economic development of the fishery sector. Monogeneans (flukes), a group of fatal metazoan parasites are recognized as a major menace to ornamental fish culture and commonly found on the gills and skin of fishes. A few may invade the internal organs like rectal cavity, ureter, body cavity or the blood vascular system. Monogenean infestation causes heavy mortality of fish population because gills are directly involved in gas transfer ion exchange and maintenance of acid base balance in the body. They also break the site of attachment and cause localized hemorrhages. At the same time, they feed upon the cells of ruptured tissue and blood. There are more than 100 families of monogeneans found in freshwater, brackish water and marine fishes of the world in various temperatures. Among these two families Gyrodactylidae and Dactylogyridae are very important as they mostly infest cyprinid fishes which have high economic value. Several workers have emphasized the significance of highly pathogenic species of these two families Gyrodactylidae and Dactylogyridae causing morbidity and mortality in ornamental fish. A detailed account of the research done on the two families Gyrodactylidae and Dactylogyridae of class Monogenea is described in this review.