Rapid evolution of antioxidant defence in a natural population of Daphnia magna

Abstract

Natural populations can cope with rapid changes in stressors by relying on sets of physiological defence mechanisms. Little is known onto what extent these physiological responses reflect plasticity and/or genetic adaptation, evolve in the same direction and result in an increased defence ability. Using resurrection ecology, we studied how a natural Daphnia magna population adjusted its antioxidant defence to ultraviolet radiation (UVR) during a period with increasing incident UVR reaching the water surface. We demonstrate a rapid evolution of the induction patterns of key antioxidant enzymes under UVR exposure in the laboratory. Notably, evolutionary changes strongly differed among enzymes and mainly involved the evolution of UV-induced plasticity. Whereas D. magna evolved a strong plastic up-regulation of glutathione peroxidase under UVR, it evolved a lower plastic up-regulation of glutathione S-transferase and superoxide dismutase and a plastic down-regulation of catalase. The differentially evolved antioxidant strategies were collectively equally effective in dealing with oxidative stress because they resulted in the same high levels of oxidative damage (to lipids, proteins and DNA) and lowered fitness (intrinsic growth rate) under UVR exposure. The lack of better protection against UVR may suggest that the UVR exposure did not increase between both periods. Predator-induced evolution to migrate to lower depths that occurred during the same period may have contributed to the evolved defence strategy. Our results highlight the need for a multiple trait approach when focusing on the evolution of defence mechanisms.

Diverging responses to threats across generations in zooplankton

“…UVR exposure also changed the reproductive strategy as individuals reared under UVR stress (with or without fish cue) showed an increased clutch size through generations. The significantly reduced clutch size during the initial exposure period (generation G1 and G2) may be due to the strong UVR‐induced oxidative damages on proteins, lipids, and DNA (Oexle et al 2016). Another reason may be that D. magna allocated energy from reproduction to photoenzymatic repair or some other mechanisms to compensate for UVR damage and therefore maintain growth, because adult size was not affected by exposure to UVR.…”

Spatial and temporal heterogeneity in climate change limits species' dispersal capabilities and adaptive potential

“…Recent advances have demonstrated that rapid, directional climatic change is not necessarily the insurmountable challenge for populations it was once believed to be (Kovach et al 2012, Gill et al 2013, Bataillon et al 2016, Franks et al 2016, Krehenwinkel et al 2016, Oexle et al 2016. Instead the difficulty posed by climate change is that rates of climatic change can vary both across time within a single region, as well across regions during a single time period (Ebi et al 2016).…”

“…For instance, following the extremely cold midwinter conditions experienced by much of continental North America in January-February 2014, surviving green anoles Anolis carolinensis exhibited both marked increases in their cold tolerances and signatures of selection across the genome (Campbell-Staton et al 2017). Similarly, rapid plastic and evolutionary responses to global climate change have already been observed across taxa ranging from migratory birds (Gill et al 2013) to anadromous fish (Kovach et al 2012), arthropods (Krehenwinkel et al 2016), annual plants (Franks et al 2016), and soil (Bataillon et al 2016) and aquatic invertebrates (Oexle et al 2016). In fact, rapid, directional climatic changes may even facilitate rapid responses (Phillips et al 2016).…”

Photodegradation and ecotoxicology of acyclovir in water under UV254 and UV254/H2O2 processes

“…The results showed an increase of the production of ROS in all samples, that could enhance the sublethal toxicity in daphnids. Aquatic organisms can in fact adapt to an increase of ROS production by upregulating the activity of their antioxidant enzymes, particularly of CAT and SOD which represent the first and the second line of defense against ROS (Oexle et al, 2016). An evident increase of ROS production in the daphnids treated with UV 254 only samples was observed in comparison to the those treated with the UV 254 /H 2 O 2 samples (Fig.…”