A laboratory model of abiotic peloid formation

Peloids are rounded grains of micritic calcite whose origin has been attributed to various biological and abiotic mechanisms. To constrain abiotic parameters that favour the formation of peloids, we precipitated calcite crusts in the absence of microorganisms. Clotted opaque fabrics that formed during the initial stages of the experiment consisted of ～10 µm peloids, while compact clear sparitic crusts precipitated in subsequent stages. The increasing supersaturation of the solution in time is responsible for this morphological succession. Initially, peloids form by the radial growth of spar crystals around a small number of nuclei. As the supersaturation increases, more spar crystals nucleate and aggregate nonradially into compact crusts. Rounded clotted precipitates are a consequence of the growth in suspension and geopetal settling, and isopachous crusts grow in the absence of these processes. Although peloids are commonly assumed to have a microbial origin, our results show that very similar morphologies can be created by purely abiotic mechanisms. Thus, the biological origin of rounded micritic calcite grains in the rock record must be verified against the abiotic null‐hypothesis in each specific case.     

Are badgers ‘Under The Weather’? Direct and indirect impacts of climate variation on European badger (Meles meles) population dynamics

Weather conditions, and how they in turn define and characterize regional climatic conditions, are a primary limit on global species diversity and distribution, and increasing variability in global and regional climates have significant implications for species and habitat conservation. A Capture–Mark–Recapture study revealed that badger (Meles meles) life history parameters interact in complicated ways with annual variability in the seasonality of temperature and rainfall, both in absolute and in phenological terms. A strong predictive relationship was observed between survival and both temperature and late‐summer rainfall. This link at the population dynamics level was related to individual body‐weight increases observed between summer and autumn. In addition, fecundity was correlated with spring rainfall and temperature. We investigated and confirmed that relationships were consistent with observed variation in the intensity of a parasitic infection. Finally, fecundity during any given year correlated with conditions in the preceding autumn. Badger survival also correlated with late winter weather conditions. This period is critical for badgers insofar as it coincides with their peak involvement in road traffic accidents (RTAs). RTA rate during this period was linked strongly to temperature, underlining the intricate ways in which a changing climate might interact with anthropogenic agents to influence species' population processes. Equinoctial conditions produced significant population driver effects. That is, while summers will always be relatively warm compared with winters, spring and autumn weather can be more variable and functionally delimit the ‘productive’ vs. nonproductive period of the year in terms of badger behavioural and physiological cycles. This study highlights how appropriately informed conservation strategies, mindful of trends in climatic conditions, will become ever‐more essential to ensure the survival of many species globally.     

The phylogenetic position of the heteropod Atlanta gaudichaudi Souleyet (Mollusca, Gastropoda), a spermatological investigation

The male adult, the spermatophore and the spermatozoa of Atlanta gaudichaudi are described. No parasperm are demonstrable. The ultrastructure of the spermatozoa is shown to differ fundamentally from that of the Archaeogastropoda and Neritopsina and to conform broadly with that of the Mesogastropoda (excepting Cyclophoracea, Viviparacea and Cerithacea), the Neogastropoda and the epitonacean heterogastropods. In having a nuclear fossa, containing the axoneme, which penetrates the entire length of the nucleus as the intranuclear canal, the spermatozoon especially resembles that of some members of the Rissoacea, Littorinacea, Eulimacea, Tonnacea, Volutacea and Conacea. Absence, in Atlanta of type 7 parasperm ( sensu Koike 1985), which characterize the Calyptraeacea, Cypraeacea, Tonnacea, Buccinacea, Volutacea (including the Mitracea) and most Conacea, or of type 8 parasperm of the Conidae, contraindicates heteropod relationship with these taxa. Relationship to the Rissoacea cannot be ruled out, though presence of oligopyrene, cusperm-like sperm in these (Bythiniidae) and pterotracheid heteropods is a questionable indication of affinity. Relationship of heteropods with the Littorinacea is suggested by similarity of the sperm, presence in carinariid heteropods and littorinids of nurse cells, and apparent homology of the male reproductive apparatus in both groups. The latter two similarities require confirmation, however. It is suggested that deposition of spermatophores on the exterior of the female in atlantid heteropods is a primitive mode of sperm transfer compatible with relationship with the Littorinacea.     

Microbe-associated molecular pattern (MAMP) signatures, synergy, size and charge: influences on perception or mobility and host defence responses

Triggering of defences by microbes has mainly been investigated using single elicitors or microbe-associated molecular patterns (MAMPs), but MAMPs are released in planta as complex mixtures together with endogenous oligogalacturonan (OGA) elicitor. We investigated the early responses in Arabidopsis of calcium influx and oxidative burst induced by non-saturating concentrations of bacterial MAMPs, used singly and in combination: flagellin peptide (flg22), elongation factor peptide (elf18), peptidoglycan (PGN) and component muropeptides, lipo-oligosaccharide (LOS) and core oligosaccharides. This revealed that some MAMPs have additive (e.g. flg22 with elf18) and even synergistic (flg22 and LOS) effects, whereas others mutually interfere (flg22 with OGA). OGA suppression of flg22-induced defences was not a result of the interference with the binding of flg22 to its receptor flagellin-sensitive 2 (FLS2). MAMPs induce different calcium influx signatures, but these are concentration dependent and unlikely to explain the differential induction of defence genes [pathogenesis-related gene 1 ( PR1 ), plant defensin gene 1.2 ( PDF1.2 ) and phenylalanine ammonia lyase gene 1 ( PAL1 )] by flg22, elf18 and OGA. The peptide MAMPs are potent elicitors at subnanomolar levels, whereas PGN and LOS at high concentrations induce low and late host responses. This difference might be a result of the restricted access by plant cell walls of MAMPs to their putative cellular receptors. flg22 is restricted by ionic effects, yet rapidly permeates a cell wall matrix, whereas LOS, which forms supramolecular aggregates, is severely constrained, presumably by molecular sieving. Thus, MAMPs can interact with each other, whether directly or indirectly, and with the host wall matrix. These phenomena, which have not been considered in detail previously, are likely to influence the speed, magnitude, versatility and composition of plant defences.     

Phototrophic Fe(II) oxidation in an atmosphere of H2: implications for Archean banded iron formations

The effect of hydrogen on the rate of phototrophic Fe(II) oxidation by two species of purple bacteria was measured at two different bicarbonate concentrations. Hydrogen slowed Fe(II) oxidation to varying degrees depending on the bicarbonate concentration, but even the slowest rate of Fe(II) oxidation remained on the same order of magnitude as that estimated to have been necessary to deposit the Hamersley banded iron formations. Given the hydrogen and bicarbonate concentrations inferred for the Archean, our data suggest that Fe(II) phototrophy could have been a viable process at this time.     

Effects of chronic chlorine exposure on litter processing in outdoor experimental streams

SUMMARY 1. The effects of chlorine on litter ( Potamogeton crispus L.) processing were examined using six outdoor experimental streams. Downstream portions of two streams were dosed at c . 10 μg l⁻¹ Total Residual Chlorine (TRC), one stream at 64 μgl¹, and one stream at 230μg l⁻¹. Two control streams were not dosed; upstream riffles of each stream served as instream controls.
2. Two 35 day litter breakdown (per cent AFDW remaining) experiments indicated significantly lower decay rates in the high dose riffle. No other concentration of chlorine significantly affected decay rate.
3. A third experiment, conducted in medium and high dose streams, indicated that high dose chlorine exposure reduced litter decomposition rates significantly, and reduced microbial colonization, microbial electron transport system activity, and microbial litter decomposition after 4 days but not after 11 days of exposure. The number of amphipod shredders colonizing litter bags was also reduced significantly with high chlorine dose.
4. A fourth experiment, after dosing was terminated, provided direct evidence that amphipod shredders were important in facilitating litter decomposition: litter bags stocked with amphipods had significantly higher decomposition rates than bags which excluded shredders.
5. Overall results indicate that the high dose (c. 230 μgl⁻¹ TRC) of chlorine reduced litter processing rates partly by reducing initial microbial conditioning, but primarily by reducing the colonization of amphipod shredders.     

BoLA antigens are associated with increased frequency of persistent lymphocytosis in bovine leukaemia virus infected cattle and with increased incidence of antibodies to bovine leukaemia virus

The association between bovine major histocompatibility system (BoLA) type and persistent lymphocytosis in cattle with antibodies to bovine leukaemia virus was examined by comparing antigen frequencies in cattle with persistent lymphocytosis to controls matched for age, sex, breed and presence of antibodies to BLV. The cattle came from nine dairy herds in south-east Queensland, Australia; six herds were Australian Illawarra Shorthorn (AIS), two herds were Jersey and one herd was Friesian. Antigen W6 and Eu28R were more common in cattle with persistent lymphocytosis than in controls. Antigen W8 was less common in AIS cattle with persistent lymphocytosis. A study of 24 offspring from one sire, heterozygous for W10 and Eu28R, showed that offspring inheriting Eu28R from the sire were significantly more likely to have antibodies to BLV than offspring inheriting the opposing W10 haplotype.