In vivo effects of UV radiation on fatty acids synthesis and expression profiles of fatty acid synthesis and antioxidant mechanisms in the cycloid copepod Paracyclopina nana

Abstract

In our previous study, we found a slight reduction in the composition of essential fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the ultraviolet (UV) radiation exposed copepod Paracyclopina nana with lipid peroxidation. To evaluate the effects of UV radiation on fatty acid synthesis, P. nana was irradiated with several doses (1,2, and 3 kJ/m2) of UV radiation. After UV irradiation, they were incubated for 48 h in dark condition with 13C labelled phytoplankton (Tetraselmis suecica). Then, the newly produced fatty acids derived from diet were measured using GC-IRMS. After incubation, 13C labelled EPA contents was significantly reduced with dose dependent manners. It suggested that the transfer of dietborn EPA was modulated under UV exposure in P. nana. The mRNA expressions of fatty acid synthesis related enzymes also modulated in UV exposed copepod. However, there was no significant change in DHA in P. nana. Additionally, no DHA contents were measured in the phytoplankton T. suecica used as a diet demonstrated that DHA is fully synthesized in copepod after feeding. Thus, we can conclude that DHA synthesis was not influenced by UV irradiation in this study. However, the reduced DHA observed in our previous study indicates DHA, already assimilated in zooplankton was affected by UV irradiation.d peroxidation. To evaluate the effects of UV radiation on fatty acid synthesis, P. nana was irradiated with several doses (1,2, and 3 kJ/m2) of UV radiation. After UV irradiation, they were incubated for 48 h in dark condition with 13C labelled phytoplankton (Tetraselmis suecica). Then, the newly produced fatty acids derived from diet were measured using GC-IRMS. After incubation, 13C labelled EPA contents was significantly reduced with dose dependent manners. It suggested that the transfer of dietborn EPA was modulated under UV exposure in P. nana. The mRNA expressions of fatty acid synthesis related enzymes also modulated in UV exposed copepod. However, there was no significant change in DHA in P. nana. Additionally, no DHA contents were measured in the phytoplankton T. suecica used as a diet demonstrated that DHA is fully synthesized in copepod after feeding. Thus, we can conclude that DHA synthesis was not influenced by UV irradiation in this study. However, the reduced DHA observed in our previous study indicates DHA, already assimilated in zooplankton was affected by UV irradiation.