Influence of temperature and spawning effort on Haliotis tuberculata mortalities caused by Vibrio harveyi: an example of emerging vibriosis linked to global warming

Since 1998, Haliotis tuberculata mass mortalities have been occurring regularly in wild abalone populations in France during their reproductive period and in conjunction with seawater summer temperature maxima and Vibrio harveyi presence. To confirm the importance of bacterial exposure, temperature and reproductive status on abalone susceptibility, experimental infections via bath exposure were performed using abalone ranging from immature to reproductively mature. Ripe abalone were more susceptible to the bacterium than immature specimens ( P <0.001), and a difference of only 1 °C in temperature had a highly significant impact on the mortalities ( P <0.001). The natural mortalities that were surveyed during summer 2007 confirmed that recent epidemic losses of European abalone appeared in conjunction with host reproductive stress, elevated temperatures and presence of the pathogen V. harveyi . In view of the elevation of the mean summer temperatures observed in Brittany and Normandy over the last 25 years, this temperature-dependent vibriosis represents a new case of emerging disease associated with global warming.     

Population decline is accompanied by loss of genetic diversity in the Lesser Grey Shrike Lanius minor

The Lesser Grey Shrike has suffered successive declines in population size and a marked contraction of its breeding range since the early 20th century, largely because of long‐term agricultural intensification. This has resulted in a severely fragmented distribution in Western Europe, with isolated breeding nuclei in Spain, France and Italy and a more continuous distribution in Eastern Europe and Asia. Using a combination of nuclear and mitochondrial markers, we assessed the genetic structure and diversity of Lesser Grey Shrike populations from Western Europe, Central Europe and Asia. There was significant genetic differentiation among three major regional groups, one European and two Asian. Genetic diversity measures were lowest in the smallest and most marginal Spanish population. Limited genetic diversity, combined with rapid population decline, suggests the Spanish population may face extinction in the near future.     

Microbial enzyme activities as indicators of organic matter processing rates in a Lake Erie coastal wetland

1. Particulate organic material (POM) is an important source of energy and nutrients in aquatic ecosystems. The decomposition of this material is typically studied using the litter bag technique. However, this method has inherent limitations that can preclude the estimation of in situ decomposition rates, especially for fine particles. In this study, we tried to circumvent these limitations through the use of enzymatic decomposition models (EDMs), which relate mass loss rates to lignocellulase activities. With this approach, we investigated the in situ processing of three size ranges of detritus in a Typha wetland. 2. Litter was collected, dried and sorted into three size ranges [coarse (C) > 4, medium (M) 0.5–4 and fine (F) 0.063–0.5 mm] and placed in litter bags that were attached to the sediment surface at two sites in a Typha wetland in May 1994. Over a 7-month period, litter bags were collected and analysed for mass loss and the activities of six extracellular enzymes involved in the degradation of lignocellulose. In situ POM was collected concurrently, sorted into the same three size ranges and assayed for the same suite of enzymes. Additional cores were taken for the determination of organic matter standing stocks and particle size distribution. 3. Mean mass loss rates for CPOM, MPOM and FPOM were -0.139, -0.073 and -0.053% day^?1, respectively. Only CPOM rates were significantly different between sites. For CPOM and FPOM there were strong linear relationships between mass loss and cumulative enzyme activities; the mass loss data for MPOM were erratic and precluded the development of reliable enzyme models. EDMs for CPOM and FPOM were constructed from regressions relating mass loss to average cumulative lignocellulase activity, and used to estimate instantaneous in situ decomposition rates. These rates varied by site and throughout the year but averaged -0.204 and -0.045% day^?1, respectively. Based upon measurements of OM standing stock and particle size distributions, POM processing rates of 1100–1400 g m² yr^?1 were calculated. These rates are near the upper end of the range for net annual production in Typha wetlands, suggesting that there is little net accumulation of POM. 4. Despite some problems, the EDM method has the potential to facilitate studies of detrital dynamics in large, heterogeneous systems.     

Use of additive models to represent trends in a barley field trial

Even when a field experiment has been designed with care, subsequent examination of the plot values may reveal additional unforeseen trends. In this paper we examine data from a barley pathology field trial and show that additive models provide a flexible representation of environmental trends, in one or two dimensions. Such models smooth out noise in the observed data, rather than fit an equation specified in advance. This approach tends to increase the precision of treatment comparisons relative to a classical analysis of variance. We recommend the use of residual plots to explore experimental data for underlying trends, and additive models to display these trends and estimate treatment effects.     

Catalytic RNA and RNA Splicing

The capacity of Watson-Crick base-pair complementarity to directinformational transactions basic to gene expression has longbeen appreciated. Among RNA molecules, it mediates mRNA-tRNAcodon-anticodon pairing and the 16S rRNA-mRNA Shine-Dalgarnointeraction. More recently, we have come to realize that therole of RNA may transcend that of intermolecular recognition,per se, to include catalysis. Following the tour-de-force studiesof the self-splicing Tetrahymena rRNA precursor, the stage isnow set for the primary role of RNA to be revealed in nuclearpre-RNA splicing, which is catalyzed by a large ribonucleoprotein(RNP) complex in the cell nucleus, called the spliceosome. Theremoval of introns from nuclear pre-messenger RNA (pre-mRNA)shares fundamental properties with certain RNA self-splicingreactions. It therefore seems likely that the major catalyticstrategies in nuclear pre-mRNA splicing are carried out by thesmall nuclear RNAs (snRNAs), which are major constituents ofthe spliceosome.     

Chemical Composition of the Epidermal, Hypodermal, Endodermal and Intervening Cortical Cell Walls of Various Plant Roots

A survey of chemical modifications in the cells of the epidermis,hypodermis, cortical parenchyma and endodermis in roots of 27plant species was performed. Cortical parenchyma walls weregenerally free of modifying substances whereas the walls ofthe epidermis, hypodermis and endodermis were usually modifiedby the presence of lipids, phenols, suberin or lignin. In mostcases, wall-modifying components could be detected within 5mm of the root apex. lipids, phenols, suberin, lignin, ferulic acid, root, epidermis, hypodermis, cortex, endodermis, cell wall     

Synthesis of Acetylcholine in the Absence of Exogenous Choline

THE breakdown of acetyl-CoA during incubation with rat brain homogenate or sections of rat nervous tissue in the absence of choline has been reported by Kasa, Mann and Hebb¹. They found that the conversion of ¹⁴C-acetyl-CoA to ¹⁴C-acetate thus incubated was considerably depressed by 10^?4 eserine or 10^?5 M di-isopropylfluorophosphate (DFP) but further depressed by 10^?3 M DFP. Experiments in our laboratories lead us to offer an explanation for that part of the breakdown inhibited by eserine or low concentrations of DFP.