Benedenia seriolae , Benedenia melleni, B.lolo et al. (<i>Benedenia seriolae</i> and benedenia mellenia)


Skin turbidity
Skin shows an over all turbidity or haze.
Gills transparent nodules
On a magnifying glass examination of the gills of a fish in a wet net, several transparent nodules can be seen.
Respiration rapid
Fish is breathing very fast, much faster than is normal.
Fish constantly rubs or scratches itself against any object available.
Fins folded
The fins of the fish remain in a closed position due to discomfort.
Raised bumps
Solid looking raised bumps are evident on the skin.
Salinity full salt water
Normal full salinity salt water.


Parasitic monogenean trematode. The parasite is translucent and hard to see. Quite common in marine aquaria.   There are few species of Benedenia Trematodes but all have a similar set of symptoms, and the treatment and prognosis are very similar.


Seldom fatal as it takes a long time to develop. If recognized the outlook is good.


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This malady is most often observed in Public and home aquaria. It is best when purchasing new specimens to watch them for a few days to see they are clear of any obvious symptoms. If need be offer the vendor a deposit and say you will collect fish after a week. 

DNA and RNA diagnostic references

Quantitative Trait Loci (QTL) Associated with
Resistance to a Monogenean Parasite (Benedenia seriolae) in Yellowtail (Seriola
quinqueradiata) through Genome Wide Analysis

From June 2013

Akiyuki Ozaki et al. 


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