Historical changes in the phenology of British Odonata are related to climate

Responses of biota to climate change take a number of forms including distributional shifts, behavioural changes and life history changes. This study examined an extensive set of biological records to investigate changes in the timing of life history transitions (specifically emergence) in British Odonata between 1960 and 2004. The results show that there has been a significant, consistent advance in phenology in the taxon as a whole over the period of warming that is mediated by life history traits. British odonates significantly advanced the leading edge (first quartile date) of the flight period by a mean of 1.51 ±0.060 (SEM, n=17) days per decade or 3.08±1.16 (SEM, n=17) days per degree rise in temperature when phylogeny is controlled for. This study represents the first review of changes in odonate phenology in relation to climate change. The results suggest that the damped temperature oscillations experienced by aquatic organisms compared with terrestrial organisms are sufficient to evoke phenological responses similar to those of purely terrestrial taxa.     

Evidence against Hydrogen–Calcium Competition Model for Activation of Electrically Excitable Membranes

TO explain the voltage-dependent sodium permeability of excitable membranes, Stephens¹ proposed a model in which sodium-selective channels are normally blocked by calcium ions bound to negatively charged sites located near the outer end of the channels. The calcium ions can be displaced competitively by hydrogen ions, opening the channels to sodium. According to this model, depolarization of an excitable membrane causes an outward flow of hydrogen ions across the membrane. The consequent transient increase in hydrogen ion concentration at the outer surface of the membrane displaces calcium and opens the sodium channels. This model is particularly interesting because it is sufficiently specific to allow direct tests. Stephens shows that it is in general agreement with a variety of experimental data. To test the model further, we have determined the effect of variation in the internal and external concentration of hydrogen ions on sodium currents.     

Portasomes as Coupling Factors in Active Ion Transport and Oxidative Phosphorylation

SYNOPSIS. We propose that particles, 7–15 nm in diameter,observed on the apical plasma membranes of cation transportingcells of insect midgut, salivary glands, and Malpighian tubulesare modified F₁-F₀ coupling complexes such as those found onphosphorylating membranes of mitochondria, chloroplasts, andbacteria. We suggest the generic term, portasome, to describeall of these particles and point out that they are located onthe side of the membrane which is electronegative and has thelow cation concentration, i.e., on the input side in each case.Biophysical evidence identifies the portasome bearing membraneas the ion transporting membrane in several insect epithelia,some of which exhibit ion modulated ATPase activity. The activityof a K⁺-modulated ATPase from Manduca sexta midgut is increasedin portasome enriched plasma membrane fractions. We proposethat portasomes orient the scalar hydrolysis of negatively chargedMgATP^2– to less negatively charged MgADP thereby eliminatingthe attraction of MgATP^2– to K⁺ with the result that theK⁺ ions are ejected to the opposite side of the portasome bearingmembrane. This mechanism explains the coupling of the scalarhydrolysis of ATP to the vectorial active transport of K⁺ whichleads to the establishment of a K⁺ electrochemical gradient.The reverse process, but with an H⁺ ionophore replacing a K⁺ionophore in the portasome, would provide a mechanism for couplingthe vectorial flow of H⁺, driven by a proton electrochemicalgradient, to scalar ATP synthesis and thereby provide a mechanismfor oxidative phosphorylation. Electrogenic active potassiumion transport would appear to have evolved from oxidative phosphorylation.