Target-site sensitivity in a specialized herbivore towards major toxic compounds of its host plant: the Na+K+-ATPase of the oleander hawk moth (Daphnis nerii) is highly susceptible to cardenolides

The caterpillars of the oleander hawk moth, Daphnis nerii (Linnaeus, 1758) (Lepidoptera: Sphingidae) feed primarily on oleander (Nerium oleander). This plant is rich in cardenolides, which specifically inhibit the Na⁺K⁺-ATPase. Since some insects feeding on cardenolide plants possess cardenolide-resistant Na⁺K⁺-ATPases, we tested whether D. nerii also possesses this strategy for circumventing cardenolide toxicity. To do so, we established a physiological assay, which allowed direct measurement of Na⁺K⁺-ATPase cardenolide sensitivity. Using Schistocerca gregaria, as a cardenolide-sensitive reference species, we showed that D. nerii Na⁺K⁺-ATPase was extremely sensitive to the cardenolide ouabain. Surprisingly, its sensitivity is even higher than that of the cardenolide-sensitive generalist, S. gregaria. The presence or absence of cardenolides in the diet of D. nerii did not influence the enzyme’s cardenolide sensitivity, indicating that target-site insensitivity is not inducible in this species. However, despite the sensitivity of their Na⁺K⁺-ATPase, caterpillars of D. nerii quickly recovered from an injection of an excessive amount of ouabain into their haemocoel. We conclude that D. nerii possesses adaptations, which enable it to feed on a cardenolide-rich diet other than that previously described in cardenolide specialized insects, and discuss other potential resistance mechanisms.     

Origin of middle rare earth element enrichment in acid mine drainage-impacted areas

The commonly observed enrichment of middle rare earth elements (MREE) in water sampled in acid mine drainage (AMD)-impacted areas was found to be the result of preferential release from the widespread mineral pyrite (FeS₂). Three different mining-impacted sites in Europe were sampled for water, and various pyrite samples were used in batch experiments with diluted sulphuric acid simulating AMD-impacted water with high sulphate concentration and high acidity. All water samples independent on their origin from groundwater, creek water or lake water as well as on the surrounding rock types showed MREE enrichment. Also the pyrite samples showed MREE enrichment in the respective acidic leachate but not always in their total contents indicating a process-controlled release. It is discussed that most probably complexation to sulphite (SO₃ ^2?) or another intermediate S-species during pyrite oxidation is the reason for the MREE enrichment in the normalized REE patterns.     

Evidence for life history changes in high-altitude populations of three perennial forbs

Relatively little is known about how the life histories of perennial forb species, and especially their lifetime patterns of growth, vary across environmental gradients. We used a post hoc approach (herb-chronology) to determine plant age and previous growth (width of successive annual rings in roots) in three species of perennial forb (two long-lived species [Penstemon venustus, Lupinus laxiflorus] and one short-lived [Rudbeckia occidentalis]) along a 1000-m altitudinal gradient in the Wallowa Mountains (northeast Oregon, USA). Plants from the highest altitude tended to be considerably older and produced up to five times as many flowering shoots as lowland plants. In addition, mean ring widths of high-altitude plants were about half those of lowland plants. In plants from low and intermediate altitudes, ring width either decreased linearly or varied inconsistently during the life of the plant. In contrast, ring widths of high-altitude plants increased at first and later decreased, resulting in curvilinear growth trajectories that were highly consistent among species. Together, these data for three ecologically distinct forb species provide evidence of a consistent shift toward more conservative and strongly constrained life histories at higher altitudes. More generally, the results indicate the possible importance of changes in selection pressures across strong environmental gradients on life history strategies within a single species.     

Multi-component analysis of polar water pollutants using sequential solid-phase extraction followed by LC-ESI-MS

A multi-component screening analysis method for polar to medium-polar water pollutants was developed. Sample clean-up and group separation are performed by sequential solid-phase extraction (SSPE) using automated SPE with C18 and polymeric sorbent materials. Analyses are performed by liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS) using a single-quadrupole instrument. More than 90 priority compounds of environmental interest--comprising the most important chemical and substance classes: phenols, carboxylic acids, aromatic sulfonates, aromatic amines, pharmaceuticals, surfactants, dyes, and pesticides--have been chosen for the experiments. The compounds are divided by the SSPE procedure into 3 different polarity classes. The extraction recoveries were determined in the 3 fractions for every single substance, and were for most of the analytes in the range of 50-100%. A mixture of hexane-dichloromethane was used for the elution of nonpolar compounds like alkylphenols from C18. Methanol and acetone are well suited for the elution of more polar substances. The limits of detection (LODs) were determined for all compounds. Effluents from municipal and industrial wastewater treatment plants (WWTPs) treating waste water from textile industries; and the corresponding receiving waters (rivers and lakes) have been analysed with the developed method. Urban and industrial pollution was observed in rivers and streams in the area north of Milan, Italy. In the water samples different phenols (nitrophenols, bisphenol A, nonylphenol), alkylphenol ethoxylate surfactants, their metabolites with endocrine disrupting potential, aromatic sulfonates, linear alkylbenzenesulfonate surfactants, dyes, pesticides, pharmaceuticals, and a dichlorobenzidine compound were identified.