Natural 15N abundance of vegetation and soil in the Kapalga savanna,Australia

Abstract The natural abundance of the stable isotope ¹⁵N was measured in different vegetation components and in the soil of a northern Australian savanna. Most of the vegetation was found to be ¹⁵N-depleted compared to atmospheric N₂. Herbaceous legumes, perennial grasses, tree legumes, non-legume trees and annual grasses exhibited mean δ¹⁵N of ? 1.7, ? 0.8, ? 0.7, 0.0 and + 0.3‰, respectively. These results are in good agreement with previous studies. Legumes exhibit slightly negative values, indicating that they are likely to be nitrogen-fixing plants. Non-legume plants have a δ¹⁵N close to zero, which could equally result from non-symbiotic fixation, soil organic matter mineralization, or fresh root litter mineralization. In contrast, soil organic matter was ¹⁵N-enriched. Values of δ¹⁵N increased with depth and were + 2.5, + 5.2 and +6.1‰ in the 0–10, 10–20 and 20–40cm layers, respectively. Soil organic matter δ¹⁵N shows a typical profile of mature soils.     

Exposure to the neonicotinoid imidacloprid disrupts sex allocation cue use during superparasitism in the parasitoid wasp Nasonia vitripennis

1. Neonicotinoid insecticides are potent neurotoxins of significant economic importance. However, it is clear that their use can adversely impact beneficial insects in the environment, even at low, sub‐lethal doses. 2. It has recently been shown that the neonicotinoid imidacloprid disrupts adaptive sex allocation in the parasitoid wasp Nasonia vitripennis (Walker) by limiting their ability to respond to the presence of other females on oviposition patches. In the present study, that work was extended to explore whether sex allocation when superparasitising – laying eggs on a host that has already been parasitised – is also disrupted by imidacloprid. 3. Under superparasitism, sex allocation theory predicts that females should vary their offspring sex ratio in relation to their relative clutch size. It was found that sex allocation under superparasitism in Nasonia is disrupted in a dose‐dependent manner, with exposed females producing more daughters. 4. Importantly, imidacloprid does not appear to influence the ability of females to estimate the number of eggs already present on a host, suggesting a disassociation between the sex ratio and clutch size cues. 5. The present work highlights the fitness costs to beneficial insects of exposure to neonicotinoids, but also provides clues as to how female Nasonia use information when allocating sex.     

Role of Energized States of (Na<Superscript>+</Superscript> + K<Superscript>+</Superscript>-ATPase in the Sodium Pump

IN an earlier paper¹ we have presented a model for a sodium pump based on the operation of the adenosine triphosphatase component of membranes which is sensitive to ouabain and is activated by sodium and potassium; that is (Na⁺+K⁺)-ATPase. We attempted to correlate the biochemical properties of this enzyme system as they were then known with the essential properties of Na⁺ transport systems. The model suggested further experiments which could clarify the role of (Na⁺ + K ⁺)-ATPase in ion transport and some experimental evidence is now available for the stoichiometry of ouabain binding to isolated enzyme preparations^2,3 although differences in the experimental techniques which have been used make the data equivocal.     

Evidence for Bicarbonate Transport in Species of Red and Brown Macrophytic Marine Algae

Cook, C. M., Lanaras, T. and Colman, B. 1986. Evidence for bicarbonatetransport in species of red and brown macrophytic marine algae.—J.exp. Bot. 37: 977–984. The capacity of 17 species of marine macrophytes to take up has been examined by comparing the rate of photosynthetic O₂-evolution with the photosyntheticrate which could be supported solely by CO₂ arising from theuncatalysed dehydration of . No external carbonic anhydrase was detected by potentiometricassay in any of the species used. At pH 8?0, the rates of photosyntheticO₂-evalution exceeded the CO₂ supply rate 6 to 24-fold in 15species of red algae, and 7 to 11-fold in 2 species of brownalgae. The ratio of photosynthetic O₂-evalution to the CO₂ supplyrate was even higher (19 to 101: 1) at pH 9?0. It is evidentfrom this data that the rate of CO₂ supply from the spontaneousbreakdown of cannot support the observed rates of photosynthesis in these algae. Thus, thedata provide substantive evidence that is taken up by these marine macrophytes as a sourceof substrate for photosynthesis. Key words: Macrophytic marine algae, bicarbonate transport     

Dispersed cuticles of putative non-vascular plants from the Lower Devonian of Britain

Dispersed cuticles with surface ornamentation recovered from the Lower Old Red Sandstone (Gedinnian) of Hereford and Worcester, England, are described, named and placed in an artificial, morphologically based classification system. Four species of the new genus Cosmochlaina are distinguished on the nature of the ornament. The affinities of the plants covered by such cuticles remain unknown: the cuticles are named to facilitate their use in biogeographic, stratigraphic and evolutionary studies.     

A migration-selection model for the morph frequency variation in the peppered moth over England and Wales

A migration-selection model for the spatial and temporal variation of morph frequencies over England and Wales for the peppered moth has been constructed. The morph frequencies have been obtained by computer simulation using the model for various assumptions regarding selection and migration within the boundaries of experimental observation. The selection, in this case, has been assumed to be wholly caused by bird predation and non-visual selection is taken to be same for all phenotypes. The results are compared with available experimental data along three transects. Reasonable agreement with the data is obtained for the Manchester-North Wales transect and the South Wales-London transect. The simulation fails, on the other hand, to reproduce observations along the Central Wales-Birmingham-East Anglia transect. Thus it is concluded that the hypothesis ol balance of selection and migration is untenable as it stands. Either the visual selection pressures are incorrectly or incompletely specified, or else non-visual selection is also operating.     

Latent Herpes Simplex Virus from Trigeminal Ganglia of Rabbits with Recurrent Eye Infection

LATENTLY infected sensory ganglia have been thought to be the source of virus for various clinical manifestations of recurrent herpetic disease in man^1,2. In direct support of this concept, we recently showed that herpes simplex virus can induce a latent infection in the spinal ganglia of mice³. This murine infection has not, however, been shown to be accompanied by recurrent disease. Recurrent herpetic eye infection can be produced in the rabbit⁴. If sensory ganglia are involved in recurrent disease, then trigeminal ganglia from rabbits undergoing such recurrent infection would be expected to harbour latent virus. We now report that herpes simplex virus does indeed induce latent infection in trigeminal ganglia of rabbits presenting recurrent eye infection. As in the experiments with mice, infectious virus could not be recovered directly; it was only found when ganglia were established as organ cultures in vitro.     

Tympanal organs of geometrid moths: a review of their morphology, function, and systematic importance

Abstract. The basic components of the tympanal organs of Geometridae are described against the background of the relevant literature. The work is prefaced by a summary of the occurrence of hearing organs within adult Lepidoptera as a whole, and the systematic value of these structures is assessed. A Latin-based nomenclature is proposed to standardize the terminology. An assessment of the morphological variation of these organs within the Geometridae was based on the study of over 230 species representing numerous examples from all the subfamilies. Morphological variation between and within the geometrid subfamilies is discussed.