Functional Ecology Group
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           Stress, cortisol and immune function in fish
                Responsible researcher: Associate professor Yngvar A. Olsen
                    Ph.D. student: Lene Valvik

         Stress affects immune function

         Chronic stress puts the body in a catabolic state and may have dire effects on immune function. The hormone cortisol is a primary mediator of stress and is increased by stressful stimuli like poor water quality or threat and fear. In fish, cortisol is produced by the interrenal cells of the kidney. Short-term stress may in some cases be beneficial to immune function, but long-lasting stress is commonly detrimental.
 

Interrenal tissue (light gray) in Atlantic salmon kidney
 
Atlantic salmon covered with fungus
 

     
     

      Artificially increasing cortisol level in Atlantic salmon leaves the fish susceptible to pathogens in the water. A common pathogen in water is fungi of the genus Saprolegnia. This organism invades the skin of the fish and the growing hyphae look like cotton-wool on the skin.
          
           Stress associated with transport or crowding in aquaculture results in increased cortisol levels. Depending on the pathogens present in the water, different diseases may occur. Vibriosis is commonly observed after moving salmon to sea water. We still have incomplete knowledge of the effect of stress on the immune system. The innate immune system is the prime candidate for investigation  concerning the detrimental effects of cortisol and stress in our research group.


     Chinook salmon with vibriosis disease
     Gills of rainbow trout
    Skin of rainbow trout



              




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 University of Agder
Faculty of Engineering and Science
Functional Ecology Group
Servicebox 422, NO-4604, Kristiansand, Norway
Phone + 47 38 14 10 70,  Fax + 47 38 14 10 71