Diel Cycles of DNA Damage and Repair in Eggs and Larvae of Northern Anchovy, Engraulis mordax, Exposed to Solar Ultraviolet Radiation

Abstract

Damage from UVB radiation (280-320 nm) in the form of cyclobutane pyrimidine dimers (CPD) in DNA and the capacity for their repair were measured in newly spawned eggs and yolk-sac larvae of northern anchovy, Engraulis mordax, exposed to natural diel cycles of sunlight. The CPD were measured by a newly developed chemiluminescent immunoblot assay capable of measuring CPD in samples as small as 50 ng DNA. Eggs and yolk-sac larvae exposed to full irradiance levels died. At lower dose rates, equivalent to deeper more natural locations in the water column, there was a diel cycle of dimer concentration that tracked solar intensity. This die1 cycle was due to the interaction of damage and repair processes. Repair of CPD in anchovy eggs and larvae could be attributed to true photodependent repair that could be stopped by moving samples into the dark.The CPD present at sunset remained until the following morning. The diel cycles of damage and repair were maintained over at least 4 days without a long-term upward or downward trend in dimer concentration. This indicates that at the UVB doses used for these experiments, there was no long-term accumulation of CPD nor an induction of increased repair capacity. Unhatched embryos spawned in the dark also exhibited a strong photorepair response, suggesting that photolyase expression was innate and not dependent on previous light exposure. The diel cycle observed here indicates that, at least for northern anchovy, the CPD concentration at the time of sampling is a good indicator of dose rate but a poor indicator of cumulative dose (i.e. late afternoon samples have the highest cumulative dose but relatively low CPD concentrations). The CPD immunoassay described here has the required sensitivity for measuring DNA damage in wild populations of ichthyoplankton exposed to natural sunlight. These results will guide the collection and interpretation of field data on natural levels of CPD in

Impact of ultraviolet radiation on marine crustacean zooplankton and ichthyoplankton:a synthesis of results from the estuary and Gulf of St. Lawrence, Canada

“…reported on DNA photorepair in UV-B exposed platyfish Xiphophorus variatus and Mitani et al (1996) observed that exposure to UV-A and blue light induced the production of cyclobutane pyrimidine dimer photolyase (involved in the repair of UV-Binduced DNA damage) in cultured cells of the goldfish Carassius auratus. Similar results on photorepair have been reported by Vetter et al (1999 (Vetter et al 1999). …”

“…Remediating effects of photorepair on UV-B-induced mortality, and DNA damage, have been reported for northern anchovy Engraulis mordax larvae (Kaup & Hunter 1981, Vetter et al 1999. reported on DNA photorepair in UV-B exposed platyfish Xiphophorus variatus and Mitani et al (1996) observed that exposure to UV-A and blue light induced the production of cyclobutane pyrimidine dimer photolyase (involved in the repair of UV-Binduced DNA damage) in cultured cells of the goldfish Carassius auratus.…”

“…Thus, these data will be used to develop BWFs for the evaluation of DNA damage in the eggs of these 2 species (Browman et al unpubl.). Such BWFs can be used to assess DNA damage to egg and Atlantic cod Gadus rnorhua eggs exposed to various spectral wavebands at the same dose rate and total dose populations exposed to sunlight, allowing a more direct evaluation of possible UV-B impacts to wild populations (sensu Vetter et al 1999). Biological weighting functions.…”

“…DNA concentration in each sample was determined with a DNA fluorometer. CPDs were measured using a chemilurninescent immunoblot assay which is thoroughly described in Vetter et al (1999).…”

UV-tolerance and instantaneous physiological stress responses of two Antarctic amphipod species Gondogeneia antarctica and Djerboa furcipes during exposure to UV radiation

“…In these species, DNA-damage and repair are simultaneous processes and UVB-induced cyclobutane pyrimidine dimers (CPDs) are repaired very rapidly within one day. This is also the case for northern anchovy eggs and larvae, where UV-induced DNA-damage (CPDs) and photoenzymatic repair happen very fast (within hours) and the daily cycle of UVR damage and photorepair follow the solar intensity, with a peak in CPD accumulation at noon, followed by a decline in CPD content until sunset, due to photorepair (Vetter et al, 1999). Dark repair during low light recovery phases in our experiments could explain oxygen consumption, 200% elevated over initial non-stressed rates.…”