Editing Monogenea (section)

== Signs and symptoms ==
[[File:Dobbeltdyr.gif|220px|thumb|''[[Diplozoon paradoxum]]'']]
Freshwater fish that become infected with this parasite become lethargic and end up swimming towards the surface of the water. In addition, some may be seen rubbing the bottom or sides of their skin where the parasite is located. Infected skin where the parasite is attached may show areas of scale loss and may produce a pinkish fluid. Gills that are infected  may appear swollen and pale. "Pipping", which is gulping for air at the water surface, could indicate severe respiratory distress.<ref name="reed" >Reed, Peggy et al. Monogenean Parasites of Fish. ''Institute of Food and Agricultural Sciences''.  . http://www.aces.edu/dept/fisheries/education/ras/publications/Update/Monogenean%20Parasites%20of%20Fish.pdf
</ref>

In salt water fish, Monogeneans can infect the skin and gills, resulting in irritations to the host. Heavy infections could result in erratic swimming behavior. Affected gills may become irritated and swollen.<ref name="reed" />