Print PageCopepods in clear, cold high elevation lakes and ponds in Colorado are exposed to significant levels of ultraviolet radiation (UV). The copepods are brightly pigmented due to accumulation of astaxanthin, a carotenoid which has photoprotective and antioxidant properties. Astaxanthin interacts with a crustacyanin-like protein, shifting the absorbance from 473 nm (hydrophobic free form, appears red) to 632 nm (protein-bound complex, appears blue). In seven sites in Colorado, habitat specific coloration patterns related to carotenoprotein complex have been observed. The objective of this study was to determine whether pigment accumulation or carotenoprotein expression has a greater effect on resistance to UV exposure. For each site, copepod tolerance to UV was assessed by survivorship during UV exposure trials. Control organisms were exposed only to the visible spectrum (shielded from UV). Average UV exposure was determined for each habitat. Astaxanthin profiles were generated and crustacyanin-like mRNA was quantified for copepods in each site.
Results/Conclusions
Ability to withstand UV exposure during exposure trials was significantly different between color morphs (p<0.0001). Red copepods were found to tolerate 2-fold greater levels of UVB than blue or mixed copepods (p<0.0001). Blue and mixed copepods did not have significantly different tolerance to UVB exposure. Additionally, preliminary data indicate that red copepods have much higher levels of total astaxanthin than blue or mixed copepods despite receiving a lower daily UV dose on average. Analysis of the carotenoprotein expression is ongoing. Carotenoprotein expression may be an important adaptation to changing UV conditions and may serve as an indicator of increasing UV exposure in high elevation lentic ecosystems.
