ABSTRACT
The fish immune system has many similarities with that of the mammalian system, but there are also some important differences. Species living a solitary existence in cold waters have rather poorly developed immune systems compared to social species in warm waters where pathogens are more easily passed between fish and the pathogens have shorter generation times due to the higher temperatures. Cadmium metal causes both immunological inhibition and stimulation in mammals, depending on a variety of factors, especially the particular immune function measured. Copper sulfate is frequently used to control external columnaris infections of pond fishes. A major class of organic contaminants that fish may get exposed to is, of course, pesticides. The general adaptation response (GAS) of fish to any sort of stress is characterized by elevations in cortisol and catecholamines. While these hormones are involved in the maintenance of homeostasis in the face of the stress, they can also have a marked effect on numerous immunological functions.
