Ergänzende Bemerkungen zur Kenntnis vonArnebia Forssk

Zusammenfassung Arnebia purpurascens (A.Rich.)Baker wird ausführlicher beschrieben, als dies in der bisherigen Literatur geschah.Arnebia euchroma (Royle) I. M.Johnst., die zur UntergattungMacrotomia (DC. exMeisn.) H.Riedl, stat. nov., zu rechnen ist, wird in drei Unterarten geteilt, nämlich ssp.euchroma, ssp.grandis H.Riedl, ssp. n. aus Südwestpersien und ssp.caespitosa Rech. f. etRiedl, ssp. n. aus Ost-Afghanistan und Chitral.Durchgeführt mit Unterstützung durch National Science Foundation Grant G 16325.     

Oxygen Dependency of Neutrophilic Fe(II) Oxidation by Leptothrix Differs from Abiotic Reaction

Neutrophilic Fe(II) oxidizing microorganisms are found in many natural environments. It has been hypothesized that, at low oxygen concentrations, microbial iron oxidation is favored over abiotic oxidation. Here, we compare the kinetics of abiotic Fe(II) oxidation to oxidation in the presence of the bacterium Leptothrix cholodnii Appels isolated from a wetland sediment. Rates of Fe(II) oxidation were determined in batch experiments at 20°C, pH 7 and oxygen concentrations between 3 and 120 μmol/l. The reaction progress in experiments with and without cells exhibited two distinct phases. During the initial phase, the oxygen dependency of microbial Fe(II) oxidation followed a Michaelis-Menten rate expression (K_M = 24.5 ± 10 μmol O₂/l, v_max = 1.8 ± 0.2 μmol Fe(II)/(l min) for 10⁸ cells/ml). In contrast, abiotic rates increased linearly with increasing oxygen concentrations. At similar oxygen concentrations, initial Fe(II) oxidation rates were faster in the experiments with bacteria. During the second phase, the accumulated iron oxides catalyzed further oxidative iron precipitation in both abiotic and microbial reaction systems. That is, abiotic oxidation also dominated the reaction progress in the presence of bacteria. In fact, in some experiments with bacteria, iron oxidation during the second phase proceeded slower than in the absence of bacteria, possibly due to an inhibitory effect of extracellular polymeric substances on the growth of Fe(III) oxides. Thus, our results suggest that the competitive advantage of microbial iron oxidation in low oxygen environments may be limited by the autocatalytic nature of abiotic Fe(III) oxide precipitation, unless the accumulation of Fe(III) oxides is prevented, for example, through a close coupling of Fe(II) oxidation and Fe(III) reduction.     

The rôle of butterfly wings in regulation of body temperature

Free and unnarcotized butterflies in a vertical basking position were exposed to radiation from a halogen lamp. Warming rate and equilibrium excess temperatures were recorded by means of microthermistors on the cuticle. Living, dead, and dried specimens were irradiated partly and totally. If the wings are shaded, the excess body temperature is reduced by about 30 per cent. The major portion of the heat transferred from the wing to the body originates from 15 per cent of the wing surface nearest to the body. There is no significant difference in excess thoracic temperatures of living and freshly dead specimens. After drying, the body temperature level rises about 1·4 to 2·2°C, remaining almost constant between 15°C (not radiated) and 37°C (radiated). The influence of air convection was tested with dried specimens under varying spatial orientation, keeping incident radiation constant. In an approximately horizontal position the heat arising from the wing increases to about 40 per cent by accumulation of warm air under the wing base. The ecological implications of heat supply by the wings and adaptive significance of wing pattern are discussed with respect to different modes of heat transport     

Citrus meletensis (Rutaceae), a new species from the Pliocene of Valdarno (Italy)

There are few fossil remains that are assigned or compared toCitrus. A new and characteristic leaf from the Pliocene of Italy is described asCitrus meletensis and its systematic position within theRutaceae is discussed. Together with other sparse remains that are reviewed here it confirms the existence ofCitrus in the European Tertiary.