Responses of the Ecological Characteristics and Antioxidant Enzyme Activities in Rotaria Rotatoria to UV-B Radiation

Background: UVB radiation is an increasing threat to aquatic organisms, and also a potential driving force for zooplankton population dynamics. The bdelloid rotifer, for its parthenogenesis and high resistance to stress, can be used as an excellent model in ecology and evolutionary biology. Given the strong tolerance of bdelloid rotifer to stressors, we hypothesized that it could hold the ability to tolerate significant UV radiation, and this capacity may be associated with the trade-off strategies among life historic components. With this study, to estimate the ecological effects and responses of antioxidant system against UV radiation, the acute lethal, life history strategies, population growth, and antioxidant enzyme activities were assessed in the bdelloid Rotaria rotatoria after exposure to UV-B radiation. Results: The persistence of tolerance (evaluating by LT50) in rotifer to stress was playing a more vital role than the radiation dose (LD50) in survival, with a significant negative correlation between the radiation intensity and LT50. The larger the culture volume, the weaker the lethal effect. Rotifers prolonged their first reproductive time (JP), and shortened their reproductive period (RP) and longevity with the increasing of radiation dose, and the fecundity was significant inhibited by UV-B radiation. These responses can be taken as energy trade-off to retard their mortality. The population density of rotifers increased at the lowest dose of radiation, and then descended with the increasing of UVR dose, and this pattern was also corroborated by detecting the content of SOD and CAT, which suggested that hormesis also applies to R. rotatoria under UV-B radiation stress. The enzyme SOD has higher level of content and more sensitive to low UVR than CAT.Conclusions: The lethal effects of UV-B radiation to organisms depends not only on the conditions they exposed to, like as intensity and time of exposure, but also combination of factors namely, the type and effectiveness of the strategy they employ to cope with the changed environment. The species specificity, ages and physiological status also could be the regulating factors under the stresses, also in this case there was the strategy of energy trade-off between reproduction and survival in rotifers.