Effects of U.V. radiation on the lifespan of the rotifer Asplanchna brightwelli

Novel Biopesticides Based on Nanoencapsulation of Azadirachtin with Whey Protein to Control Fall Armyworm

Biopesticides have become a global trend in order to minimize the hazards derived from synthetic chemical pesticides and improve the safety, efficacy, and environmental friendliness of agricultural pest management. Herein, we report a novel biopesticide composite encapsulating azadirachtin with the size of 260.9 ± 6.8 nm and its effects on the insect pest Spodoptera frugiperda (fall armyworm). The nanocomposite biopesticide was produced via nano emulsification and freeze-drying process using whey protein isolate as a nanocarrier matrix to encapsulate azadirachtin, a natural insect-killing compound obtained from neem seed. We found that the nanocomposite biopesticide acted quicker and with greater efficacy than bulk azadirachtin treatment with corresponding LC₅₀ values within 11 days of S. frugiperda larvae survival. Through confocal microscopy, we found the enhanced biodistribution of the nanocomposite to all parts of the insect body. Photodegradation assays revealed an enhanced UV stability facilitated by light-scattering stemming from the intrinsic nanostructure and UV scavenging vitamin-E component.

UV-induced DNA damage in Cyclops abyssorum tatricus populations from clear and turbid alpine lakes

Zooplankton from clear alpine lakes thrive under high levels of solar UV radiation (UVR), but in glacially turbid ones they are more protected from this damaging radiation. Here, we present results from experiments done with Cyclops abyssorum tatricus to assess UV-induced DNA damage and repair processes using the comet assay. Copepods were collected from three alpine lakes of differing UV transparency ranging from clear to glacially turbid, and exposed to artificial UVR. In addition, photoprotection levels [mycosporine-like amino acids (MAAs) and lipophilic antioxidant capacity] were estimated in the test populations. Similar UV-induced DNA damage levels were observed among the copepods from all lakes, but background DNA damage (time zero and dark controls) was lowest in the copepods from the glacially turbid lake, resulting in a higher relative DNA damage accumulation. Most DNA strand breaks were repaired after recovery in the dark. Low MAA concentrations were found in the copepods from the glacially turbid lake, while the highest levels were observed in the population from the most UV transparent lake. However, the highest lipophilic antioxidant capacities were measured in the copepods from the lake with intermediate UV transparency. Photoprotection and the ability to repair DNA damage, and consequently reducing UV-induced damage, are part of the response mechanisms in zooplankton to changes in water transparency caused by glacier retreat.

UV radiation and freshwater zooplankton: damage, protection and recovery

While many laboratory and field studies show that zooplankton are negatively affected when exposed to high intensities of ultraviolet radiation (UVR), most studies also indicate that zooplankton are well adapted to cope with large variations in their UVR exposure in the pelagic zone of lakes. The response mechanisms of zooplankton are diverse and efficient and may explain the success and richness of freshwater zooplankton in optically variable waters. While no single behavioural or physiological protection mechanism seems to be superior, and while several unexplained and contradictory patterns exist in zooplankton UVR ecology, recent increases in our understanding are consistent with UVR playing an important role for zooplankton. This review examines the variability in freshwater zooplankton responses to UVR, with a focus on crustacean zooplankton (Cladocera and Copepoda). We present an overview of UVR-induced damages, and the protection and recovery mechanisms freshwater zooplankton use when exposed to UVR. We review the current knowledge of UVR impact on freshwater zooplankton at species and community levels, and discuss briefly how global change over the last three decades has influenced the UVR milieu in lakes.

The effects of UV radiation and antioxidants on life span and lipid peroxidation in the rotifer Asplanchna brightwelli

Lipid peroxidation (LP) rates and life span were determined in control and in ulraviolet (UV) irradiated rotifers of the species Asplanchna brightwelli. UV irradiation administered at 6 h of life significantly increased the rate of LP as the rotifers aged; it also produced a significant shortening of rotifer life span. Pretreatment with 20 microg/ml of vitamin E blocked the increase in LP and the decrease in life span induced by UV radiation. The antioxidant synergist 3,3'-thiodipropionic acid had no such UV-protective effect. These results indicate that the decrease in life span caused by UV radiation may be mediated through the production of lipid peroxides.

UV Damage and Photoreactivation: Timing and Age are Everything¶

Aquatic organisms, ranging from bacteria to fish, living in clear lakes are presently receiving damaging levels of UV radiation. Photoreactivation is a light-dependent mechanism by which some organisms deal with DNA damage caused by UV radiation. Yet, photoreactivation is a mechanism that confounds long-term predictive modeling of UV effects on the survival of these organisms. Here we show that a short-lived rotifer species, Asplanchna girodi, previously thought to have little to no photoreactivation, does indeed have a significant amount of it. The ability to undergo photoreactivation in A. girodi is dependent on age and becomes apparent only after several days of observation after UV exposure.

UV-B exposure increases acute toxicity of pentachlorophenol and mercury to the rotifer Brachionus calyciflorus

Adverse biological effects of ultraviolet-B (UV-B) radiation have been well documented for phytoplankton and zooplankton in both marine and freshwater ecosystems. However, investigations of interactions between UV-B and anthropogenic toxicants have focused primarily on the chemical interactions between UV-B and the toxicant. Here we investigate the potential for UV-B to increase the sensitivity of the rotifer Brachionus calyciflorus to either acute pentachlorophenol (PCP) or mercury toxicity, independent of UV-B effects on these toxicants. UV-B increased the toxicity of PCP and mercury to B. calyciflorus as much as five-fold, depending on duration of UV-B exposure and toxicant concentration. Reductions in the LC(50) of up to 60% were also seen for both toxicants. UV-B alone effectively eliminated B. calyciflorus reproduction and reduced ingestion by up to 90%. These results demonstrate the potential for UV-B to increase rotifer sensitivity to anthropogenic stressors independent of photochemical reactions with toxicants.

Biochemical changes associated with the mechanism controlling superoxide radical formation in the aging rotifer

Levels of the superoxide radical (SOR) and lipid peroxides were measured and found to increase during aging in the short-lived rotifer, Asplanchna brightwelli. Life-span was altered by changes in environmental temperature, absence of light, diet restriction, exposure to ultraviolet radiation, and addition of vitamin E to the diet. Each of the conditions that lengthened life-span decreased SOR and lipid peroxide levels, and each condition that shortened life-span increased levels of SOR and lipid peroxides. Additional experiments indicated that on the third day of age, there was a significant increase in Ca2+ uptake and phospholipase A2 activity in membrane samples and an elevation in superoxide dismutase and catalase activity in rotifer homogenates. In addition, SOR concentration was inhibited by the addition of bromophenacyl bromide and indomethacin to membrane samples. By day 5 there was also a significant increase in the lysosomal enzyme, alpha-mannosidase. The results of this study indicate that levels of the SOR and lipid peroxides are coupled to rotifer life-span and that activation of phospholipase A2 may contribute to the elevation of these agents in older animals.