Effects of UV-radiation on oxidative stress parameters in polar marine amphipods, and the role of UV-absorbing mycosporine-like amino acids (MAAs) in their diet

This study investigates the impact of elevated UVB radiation on UV-transparent Antarctic shallow water amphipods with respect to UV-induced oxidative stress in animal cells. Transfer of UV absorbing macroalgal-derived mycosporine-like amino acids (MAAs) was studied, to assess the importance of the algal diet for UV and antioxidant protection in crustaceans. Animals were exposed to artificial UVB light up to four weeks in the laboratory. Mortality increased to roughly 10% of exposed amphipods under moderate UVB dose (42-54% of shallow water in-situ dose, i.e. 21-27% of natural atmospheric dose over exposure time) and to a maximum of 28% under high UVB exposure (50-93% increase of shallow water in-situ dose, i.e. 75-97% of natural atmospheric dose over exposure time) in animals not fed with macroalgae over 14 days. By contrast, the state of nutrition does not seem to affect antioxidant protection and lipid peroxidation directly as no significant differences between fed and non-fed animals could be detected. Variability of in-situ values was high for superoxid-dismutase (SOD) and malondialdehyde (MDA) accumulation. SOD activity increased under moderate, and decreased during high dose UVB exposure. Lipid peroxidation (MDA) decreased after three weeks of low dose UVB exposure and exhibited a slight increase under high dose UVB. Batch uptake of MAAs from algal food was not increased under experimental high dose UVB exposure over 3 weeks, and mycosporine-glycine and P-334 were the only compounds that accumulated in exposed animals. Without UVB (cut-off filter) mycosporine-glycine as well as P-334 and palythine decreased during the experiment compared to initial values. This suggests a better conservation of individual MAAs under UVB exposure and a faster degradation of these sunscreening compounds in UVB non-irradiated amphipods.