Mitochondria are thought to have a biphasic response to the production of reactive oxygen species (ROS), where low levels of ROS benefit mitochondrial performance and high levels are damaging. As such, we hypothesized that moderate ROS production would lead to more advantageous life history characteristics, possibly caused by the upregulation of antioxidants, biogenesis, or repair mechanisms. We used UV-B light as an oxidant to determine if moderate ROS production has any positive or negative influence on life history characteristics in a marine copepod (Tigriopus californicus). We measured longevity, clutch frequency, gestation length, and nauplii production between a control group (full-spectrum lighting without UV-B) and both short (1 hour) and long-term (3 hour) UV-B treatments. We used zero-inflated negative binomial, Poisson, and linear regression to examine variation in life history characteristics while controlling for age.
Results/Conclusions
We found that longer UV-B exposure lead to greater first clutch fecundity among females that reproduced. However, UV-B exposure had no effect on whether or not females produced clutches. In addition, females that did produce clutches (versus those that did not) tended to live longer; more specifically, higher clutch frequencies lead to greater longevity. UV-B exposure did not seem to have any significant effect on gestation length or clutch frequency. These findings indicate possible benefits to moderate UV-B exposure. Individuals with increased mitochondrial function may therefore be better adapted to survive and reproduce within a given population. Hence, exposure to such oxidants may explain certain light-dependent behaviors (e.g., diel vertical migration) in organisms such as copepods.