The ability to photorepair UV damaged DNA and the rate of photoreactivation in Antarctic species compared with temperate and tropical species

Time course experimental exposure of the Antarctic sea urchin Sterechinus neumayeriembryos to UVR was carried out in a lab to examine the kinetics of UVR induced damage to DNA. Embryos (freshly fertilized embryos, blastula and 4 armed larvae) were exposed to artificial light with samples taken at 0, 1, 2, 6, 12 and 24 hours post exposure. Cyclobutane pyrimidine dimers (CPDs) were quantified. To obtain a measure of the rate of photoreactivation, the disappearance of CPDs over time in embryos that were either able to photorepair or were photorepair inhibited in two Antarctic species (Sterechinus neumayeri and Odontaster meridionalis) a temperate species (Pseudechinus huttoni) and two tropical species (Arachnoides spp. and Diadema spp.) was determined. The embryos were exposed to UVB for 1 hour then allowed to photorepair by placement under a full spectrum light or total darkness. Samples were taken at 0, 1, 2, 6, 12 and 24 hours post UV exposure. DNA photoproducts were detected by an enzyme-linked immunoabsorbent assay. The effect of temperature on DNA repair rate was quantified by running the above experiment at various temperatures depending on species. For Antarctic species, experiments were conducted at -1.9, 0 and 2.0 �C, for temperate species at 5, 10 and 15�C and tropical species at 23.5, 28 and 32�C. Time to repair 50% and 80% of the damage and percent repaired after 24 hours was calculated for each Antarctic species and compared with the temperate and tropical species.