The effects of sub-lethal doses of dichlorvos and formalin, antimicrobial/parasitic agents used in aquaculture, on lipid composition and metabolism of rainbow trout skin cells in primary culture were investigated. Both dichlorvos and, especially, formalin appeared to significantly inhibit Î9 and Î6
desaturase.Changes in the distribution of radioactivity between individual phospholipid classes was also influenced by formalin and dichlorvos, and this may be related to changes in desaturase activity. This study has shown that topically active agents used in aquaculture, formalin and dichlorvos, had a range of effects on the rainbow trout skin cell cultures that may affect cell proliferation and lipid and fatty acid metabolism. Both agents significantly inhibited desaturation of fatty acids, particularly of 18:2n-6 to 20:4n-6 and, as 20:4n-6 is a major eicosanoid precursor in fish and considering the importance of eicosanoids in the biochemistry of skin ,it is suggested that these agents may have direct effects on fish skin that may have important consequences for fish health in general.3