Jorge A. Masso-Silva and Gill Diamond
Pharmaceuticals 2014, 7(3), 265-310; doi:10.3390/ph7030265
“AMP” = antimicrobial peptide
Piscidins exhibit potent antimicrobial activity against a variety of microorganisms.
They are widely active against bacteria Gram-positive and -negative species…
Piscidins have also been shown to possess anti-fungal activity, anti-parasitic activity, and anti-viral activity.
Piscidins are mainly expressed in gill, skin and intestine, although can be also found in head-kidney and spleen. However, in Atlantic cod piscidin was found to be ubiquitous, being detected in chondrocytes, heart, oocytes, exocrine and endocrine glands, swim bladder, and other tissues.
Like AMP genes from mammals, piscidin genes can be induced by a variety of stimuli, including Gram-positive and -negative bacteria, bacteria cell components like LPS or the bacterial antigen ASAL.
Furthermore, piscidin genes are induced by parasites, viruses,…
Another study demonstrated that high biomass density (i.e., a higher concentration of fish per volume water in an experimental tank) used as an acute stressor component, led to an to up-regulation of dicentracin in gills and skin as well.
Histone-derived AMPs have been identified in a number of fish species, with broad-spectrum activity against both human and fish pathogens, including water molds and a parasitic dinoflagellate. They are expressed and secreted in fish skin, and found in other tissues, including gill, speen and the gut.
Further evidence that they play a role in host defense of the fish comes from studies showing that expression of histone-derived AMP genes are induced under conditions of stress in specific tissues of different fish species.
This is just a sample of quotes that focuses only on piscidins and histidins, where the review article goes on at length with lots more good info.
There really should be no doubt about a healthy fish’s ability to defend itself.
The doubt should be focused on whether, or how much, we limit or support their abilities with stress and nutrition.