The population biology of Ligia oceanica (L.)(Crustacea: Oniscoidea)

The dynamics and life history of an isolated population of Ligia oceanica (L. ) inhabiting a sea-wall exposed to moderate wave action have been studied over a period of three years. Sex ratio, size at maturity, growth, breeding phenology, size and age structure, population density and size, female breeding size, fecundity regression and broodpouch mortality have been determined. From these data population natality, and schedules of survivorship, fecundity and reproductive value are calculated. Although the supralittoral zone of rocky shores is generally regarded as a severe and stressful habitat, the dynamics of the population exhibit only minor differences between years, and no direct influence of wave exposure can be determined. This population is compared with another nearby but isolated population occupying an harbour wall completely protected from wave action. These populations are presumed to suffer different levels of density-independent mortality due to the wave exposure characteristics of the sites. The sheltered site population shows no significant differences between the two years of study. Interpopulation differences in age and size structure, growth rate, population breeding phenology and breeding sizes are slight. However the sheltered population shows increased adult survival and longevity, decreased weight specific fecundity and reproductive allocation, and increased brood-pouch mortality. Because winter survival is high, when mortality due to wave action is expected to be severe, this factor is rejected as an important determinant of the life history. The reduced survival at the exposed site can be interpreted as a consequence of the increased reproductive allocation by individuals at this site. The majority of females are semelparous, but within both populations two distinct waves of breeding activity occurred each year. Larger, faster growing individuals breed at the end of their first ýear, LATE in the season, and have high weight specific fecundities and low absolute and weight specific egg sizes. Smaller, slower growing individuals delay reproduction and breed in their second year, EARLY in the season. Although gaining greatly in size through growth the effect on fecundity is offset by a decrease in weight specific fecundity and parallel increases in absolute and weight specific egg size. The following trade-offs are recognised for individual female Ligia : between growth and reproduction (within breeding groups), growth and reproduction (between breeding groups), reproduction and survival (between breeding groups), weight specific egg size and weight specific fecundity (between breeding groups), and between absolute egg size and fecundity (within breeding groups). Two possible life history strategies are recognised. (i) An ability of a female parent to alter egg size seasonally may optimise total offspring fitness in the different environments they experience.(ii) An ability of small, mature females to delay reproduction until the following year may also increase their fitness. By assuming that offspring survival is related to egg size it is possible to model this tactic. The population breeding phenology is seen as a direct consequence of the life history and has the indirect effect of stabilizing the population. The ability of individual females to vary their life history traits depending on individual circumstances (size and season) may represent a flexible approach to the environment which is not envisioned in the more formal models of life history evolution

Modelling sediment supply and transport in the River Lugg: strategies for controlling sediment loads

The River Lugg has particular problems with high sediment loads that have resulted in detrimental impacts on ecology and fisheries. A new dynamic, process-based model of hydrology and sediments (INCA- SED) has been developed and applied to the River Lugg system using an extensive data set from 1995–2008. The model simulates sediment sources and sinks throughout the catchment and gives a good representation of the sediment response at 22 reaches along the River Lugg. A key question considered in using the model is the management of sediment sources so that concentrations and bed loads can be reduced in the river system. Altogether, five sediment management scenarios were selected for testing on the River Lugg, including land use change, contour tillage, hedging and buffer strips. Running the model with parameters altered to simulate these five scenarios produced some interesting results. All scenarios achieved some reduction in sediment levels, with the 40% land use change achieving the best result with a 19% reduction. The other scenarios also achieved significant reductions of between 7% and 9%. Buffer strips produce the best result at close to 9%. The results suggest that if hedge introduction, contour tillage and buffer strips were all applied, sediment reductions would total 24%, considerably improving the current sediment situation. We present a novel cost-effectiveness analysis of our results where we use percentage of land removed from production as our cost function. Given the minimal loss of land associated with contour tillage, hedges and buffer strips, we suggest that these management practices are the most cost-effective combination to reduce sediment loads

Structure of the Mg-Chelatase Cofactor GUN4 Reveals a Novel Hand-Shaped Fold for Porphyrin Binding

In plants, the accumulation of the chlorophyll precursor Mg-protoporphyrin IX (Mg-Proto) in the plastid regulates the expression of a number of nuclear genes with functions related to photosynthesis. Analysis of the plastid-to-nucleus signaling activity of Mg-Proto in Arabidopsis thaliana led to the discovery of GUN4, a novel porphyrin-binding protein that also dramatically enhances the activity of Mg-chelatase, the enzyme that synthesizes Mg-Proto. GUN4 may also play a role in both photoprotection and the cellular shuttling of tetrapyrroles. Here we report a 1.78-Å resolution crystal structure of Synechocystis GUN4, in which the porphyrin-binding domain adopts a unique three dimensional fold with a “cupped hand” shape. Biophysical and biochemical analyses revealed the specific site of interaction between GUN4 and Mg-Proto and the energetic determinants for the GUN4 • Mg-Proto interaction. Our data support a novel protective function for GUN4 in tetrapyrrole trafficking. The combined structural and energetic analyses presented herein form the physical-chemical basis for understanding GUN4 biological activity, including its role in the stimulation of Mg-chelatase activity, as well as in Mg-Proto retrograde signaling

The \u3cem\u3eChlamydomonas\u3c/em\u3e Genome Reveals the Evolution of Key Animal and Plant Functions

Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the ∼120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella

Do sugar-sweetened beverages cause adverse health outcomes in adults? A systematic review protocol

Background: Chronic diseases, such as cardiovascular disease and type 2 diabetes, impose significant burden to public health. Most chronic diseases are associated with underlying preventable risk factors, such as elevated blood pressure, blood glucose, and lipids, physical inactivity, excessive sedentary behaviours, overweight and obesity, and tobacco usage. Sugar-sweetened beverages are known to be significant sources of additional caloric intake, and given recent attention to their contribution in the development of chronic diseases, a systematic review is warranted. We will assess whether the consumption of sugar-sweetened beverages in adults is associated with adverse health outcomes and what the potential moderating factors are. Methods/Design: Of interest are studies addressing sugar-sweetened beverage consumption, taking a broad perspective. Both direct consumption studies as well as those evaluating interventions that influence consumption (e.g. school policy, educational) will be relevant. Non-specific or multi-faceted behavioural, educational, or policy interventions may also be included subject to the level of evidence that exists for the other interventions/exposures. Comparisons of interest and endpoints of interest are pre-specified. We will include randomized controlled trials, controlled clinical trials, interrupted time series studies, controlled before-after studies, prospective and retrospective comparative cohort studies, case-control studies, and nested case-control designs. The MEDLINE®, Embase, The Cochrane Library, CINAHL, ERIC, and PsycINFO® databases

Withering Waits: the Development of a Referrals Management System Within a Clinical Psychology & Counselling Service

This paper charts the implementation and development of a referrals management system within a secondary care National Health Service (NHS) clinical psychology and counselling service over a period of approximately three years. The new system that is described has brought about dramatic reductions in numbers waiting for both assessment and therapy, as well as modest improvements in attendance rates at first assessment. Other changes have resulted from the new system, such as a more unified, transparent and collaborative approach, a move to more of a consultation model of assessment and an expansion in the breadth of clinicians’ roles. The paper explores the challenge of having to continue to meet a demand that far outstrips the available resources. This raises dilemmas in clinical decision-making, in the positioning of the department in relation to referrers, and in maintaining an efficient service with minimal waiting lists without losing the depth and variety of work that are strengths of the department

Biosynthesis of chlorophylls from protoporphyrin IX

15 page(s

Chlorophylls

34 page(s