Oviposition,larval survival and leaf damage by the willow leaf blotch miner,Micrurapteryx salicifoliella,in relation to leaf trichomes across 10 Salix species

1. Foliar trichomes clearly reduce chewing damage and efficiency of movement by some insect herbivores, but the effect of trichomes on insect oviposition is less well characterised. Trichomes are likely to have particularly strong, negative effects on species that require secure attachment of the egg to the leaf epidermis for successful transition to the feeding stage – a group that includes many leaf mining insects. 2. One such species, Micrurapteryx salicifoliella, must initially enter leaf cells directly from an egg adhered to the cuticle, but later instars can move between leaves and initiate new mines from the leaf exterior. 3. Natural patterns of occurrence by M. salicifoliella were quantified on 10 sympatric Salix species varying in trichome expression to test whether trichomes were associated with reduced oviposition, larval survival and leaf damage. 4. Mean egg density and leaf mining damage were negatively related to mean trichome density across Salix species. Survival of M. salicifoliella from egg to pupa was positively related to trichome density, suggesting that initiation of new mines by late‐instar larvae was not adversely affected by trichomes. There was no evidence that trichomes benefited leaf miner larvae indirectly by decreasing density‐dependent mortality; rather, the positive relationship between trichome density and larval survival may reflect less effective chemical defence by Salix species expressing high trichome density. 5. The results suggest that foliar trichomes serve as an effective defence against M. salicifoliella by deterring oviposition, but do not reduce the survivorship of those individuals that successfully transition from egg to larva.     

Ecological and genetic correlates of range expansion in Coenonympha tullia

Range expansion by the North American butterfly species Coenonympha tullia is associated with dramatic changes in life history and in genetic and morphological variation. Eight of ten independent, variable loci exhibit step-clines in allele frequency; step-clines also occur in four wing pattern characters. Populations from the old part of the range are univoltine, and have significantly less genetic and morphological variation than populations from the recently colonized ranger, which arc bivoltine. The concordance of life history with genetic and morphological variation suggests that differences between univoltine and bivoltine populations are maintained by selection. Increased electrophoretic variation in the recently colonized range may have arisen by selection on rare variants within the old part of the range.     

Ornithine Decarboxylase in Trypanosoma brucei brucei: Evidence for Selective Toxicity of Difluoromethylornithine1

ABSTRACT. Activity of ornithine decarboxylase, the major rate limiting enzyme of polyamine biosynthesis, was determined in bloodstream trypomastigotes of Trypanosoma brucei brucei. The enzyme required pyridoxal-5′-phosphate, dithiothreitol and EDTA for optimal activity. Several properties of the enzyme were investigated and compared to the mammalian enzyme. Most notably, the parasite enzyme was >60-fold more sensitive to the inhibitor DL-α-difluoromethylornithine than its mammalian counterpart, thus making it an attractive target for chemotherapy.     

Mechanical significance of ammonoid septa with complex sutures

Pre- and post-19th century hypotheses relating hydrostatic pressure to the mechanical function of sutural complexity are compared. The old ideas gave rise to the 19th century 'Buckland hypothesis', which is in turn largely synonymous with the 'Westermann model'. Buckland (1836) postulated that fluted septa buttressed the weak flanks of the phragmocone wall. Two new parameters are introduced to define the covariation between the strength of cylindrical segments of the wall flank bounded by the distance between adjacent lobe and saddle-flutes in transverse sections. The product of the index of wall strength (IWS) and this inverse support angle (ISA) predicts the buckling pressure in a cylinder of infinite length, and it implies that coiled nautiloids were more likely to be imploded via their whorl flanks than the apparently weaker oxyconic ammonoids. The widely used index of sutural complexity (ISC) measures the marginal corrugation which obscures this trend and acts as an elastic bed for both strong and weak walls. However, the ISC is more proportional to habitat depth than the buckling pressure when all other factors are constant. The central thickness of each fluted septum was increased in direct proportion to the distance spanned by the septum and the hydrostatic pressure on it in the 'last septum' position. The marginal thickness was maintained at a more constant value, which permitted the suture to increasingly act like a spring or shock absorber, as the wall thickness was enlarged during ontogeny. Both the ratios, between the central and marginal thicknesses and the closely related ISC, therefore, increased with shell diameter and habitat depth.     

Extracellular Amastigote-Like Forms of Leishmania panamensis and L. braziliensis. II. Stage- and Species-Specific Monoclonal Antibodies

Immunochemical evidence, employing monoclonal antibodies, shows that the forms of L. braziliensis complex axenically grown at elevated temperature are amastigote-like. The monoclonal antibodies were raised against membrane proteins of amastigote-like forms, strains of both L. panamensis (WR442) and L. braziliensis (M5052), which were grown axenically. The specificities of these antibodies were examined by indirect radioimmune binding assay, indirect immunofluorescent assay and Western blot analyses. Two distinct groups of monoclonal antibodies were obtained and their specificities were consistent with the 3 methods used. Four antibodies are specific for the species L. panamensis and react with both developmental stages. Six antibodies specifically recognize amastigote-like forms grown at elevated temperature and intracellular amastigotes of both L. panamensis (WR442) and L. braziliensis (M5052). These monoclonal antibodies do not bind to promastigotes of these species, nor to promastigotes of any other species of Leishmania . Therefore these antibodies are specific for amastigotes of L. panamensis (WR442) and L. braziliensis (M5052), and suggest that immunochemically both amastigote forms (culture and macrophage) are developmentally very close, if not identical. The molecules associated with the amastigote-specific antigenic determinants consist of a Mr 12-kD component and a heterogeneous component (Mr from 50 kD to >200 kD); these molecules appear to be identical for both amastigote-like forms and amastigotes isolated from macrophages.     

Impact of rising CO2 on emissions of volatile organic compounds: isoprene emission from Phragmites australis growing at elevated CO2 in a natural carbon dioxide spring†

Isoprene basal emission (the emission of isoprene from leaves exposed to a light intensity of 1000 µmol m^?2 s^?1 and maintained at a temperature of 30 °C) was measured in Phragmites australis plants growing under elevated CO₂ in the Bossoleto CO₂ spring at Rapolano Terme, Italy, and under ambient CO₂ at a nearby control site. Gas exchange and biochemical measurements were concurrently taken. Isoprene emission was lower in the plants growing at elevated CO₂ than in those growing at ambient CO₂. Isoprene emission and isoprene synthase activity (IsoS) were very low in plants growing at the bottom of the spring under very rich CO₂ and increased at increasing distance from the spring (and decreasing CO₂ concentration). Distance from the spring did not significantly affect photosynthesis making it therefore unlikely that there is carbon limitation to isoprene formation. The isoprene emission rate was very quickly reduced after rapid switches from elevated to ambient CO₂ in the gas‐exchange cuvette, whereas it increased when switching from ambient to elevated CO₂. The rapidity of the response may be consistent with post‐translational modifications of enzymes in the biosynthetic pathway of isoprene formation. Reduction of IsoS activity is interpreted as a long‐term response. Basal emission of isoprene was not constant over the day but showed a diurnal course opposite to photosynthesis, with a peak during the hottest hours of the day, independent of stomatal conductance and probably dependent on external air temperature or temporary reduction of CO₂ concentration. The present experiments show that basal emission rate of isoprene is likely to be reduced under future elevated CO₂ levels and allow improvement in the modelling of future isoprene emission rates.