Climate‐induced changes in the distribution of freshwater fish: observed and predicted trends

1. Climate change could be one of the main threats faced by aquatic ecosystems and freshwater biodiversity. Improved understanding, monitoring and forecasting of its effects are thus crucial for researchers, policy makers and biodiversity managers. 2. Here, we provide a review and some meta‐analyses of the literature reporting both observed and predicted climate‐induced effects on the distribution of freshwater fish. After reviewing three decades of research, we summarise how methods in assessing the effects of climate change have evolved, and whether current knowledge is geographically or taxonomically biased. We conducted multispecies qualitative and quantitative analyses to find out whether the observed responses of freshwater fish to recent changes in climate are consistent with those predicted under future climate scenarios. 3. We highlight the fact that, in recent years, freshwater fish distributions have already been affected by contemporary climate change in ways consistent with anticipated responses under future climate change scenarios: the range of most cold‐water species could be reduced or shift to higher altitude or latitude, whereas that of cool‐ and warm‐water species could expand or contract. 4. Most evidence about the effects of climate change is underpinned by the large number of studies devoted to cold‐water fish species (mainly salmonids). Our knowledge is still incomplete, however, particularly due to taxonomic and geographic biases. 5. Observed and expected responses are well correlated among families, suggesting that model predictions are supported by empirical evidence. The observed effects are of greater magnitude and show higher variability than the predicted effects, however, indicating that other drivers of changes may be interacting with climate and seriously affecting freshwater fish. 6. Finally, we suggest avenues of research required to address current gaps in what we know about the climate‐induced effects on freshwater fish distribution, including (i) the need for more long‐term data analyses, (ii) the assessment of climate‐induced effects at higher levels of organisation (e.g. assemblages), (iii) methodological improvements (e.g. accounting for uncertainty among projections and species’ dispersal abilities, combining both distributional and empirical approaches and including multiple non‐climatic stressors) and (iv) systematic confrontation of observed versus predicted effects across multi‐species assemblages and at several levels of biological organisation (i.e. populations and assemblages).     

Distinct functions of DC-SIGN and its homologues L-SIGN (DC-SIGNR) and mSIGNR1 in pathogen recognition and immune regulation

Antigen presenting cells express C-type lectins that are involved in pathogen capture, processing and antigen presentation to induce immune responses against these pathogens. However, it is becoming clear that pathogens have evolved to subvert the function of some C-type lectins to escape immune surveillance. An important C-type lectin family is represented by DC-SIGN and its homologues in human and mouse. Here we discuss the structure in relation to the pathogen binding specificity of the SIGN receptors and the function of these receptors in mouse and humans.     

Enzyme immobilization via monoclonal antibodies I. Preparation of a highly active immobilized carboxypeptidase A

A novel method for the preparation of highly active immobilized enzymes is described. It is based on the binding of enzymes to suitable carriers via monoclonal antibodies, which bind to the enzyme with high affinity without affecting its catalytic activity. The applicability of the method forwarded has been illustrated by the preparation of two samples of highly active immobilized carboxypeptidase A (CPA) preparations as follows: A mouse monoclonal antibody (mAb 100)to CPA that binds to the enzyme with a high-affinity constant without affecting its catalytic activity was prepared, purified, and characterized. Covalent binding of this monoclonal antibody to Eupergit C (EC) or noncovalent binding to Sepharose-protein A (SPA)yielded the conjugated carriers EC-mAb and SPA.mAb, respectively, which reacted specifically with CPA to give the immobilized enzyme preparations EC-mAb.CPA and SPA.mAb.CPA displaying full catalytic activity and improved stability. At pH 7.5 and a temperature range of 4-37 degrees C an apparent binding constant of approximately 10(8)M(-1) characterizing the interaction of CPA with EC-mAb and SPA.mAb, was obtained. To compare the properties of EC-mAb.CPA and SPA.mAb.CPA with those of immobilized CPA preparations obtained by some representative techniques of covalent binding of the enzyme with a corresponding carrier, the following immobilized CPA preparations were obtained and their properties investigated: EC-CPA (I), a preparation obtained by direct binding of EC with CPA; EC-NH-GA-CPA (II), a derivative obtained by covalent binding of CPA to aminated EC via glutaraldehyde; EC-NH-Su-CPA (III), a CPA derivative obtained by binding the enzyme to aminated EC via a succinyl residue; and EC-HMD-GA-CPA (IV), obtained by binding the enzyme via glutaraldehyde to a hexamethylene diamine derivative of EC. Full enzymic activity for all of the bound enzyme, such as that recorded for the immobilized CPA preparations EC-mAb.CPA and SPA.mAb.CPA, was not detected in any of the insoluble covalently bound enzyme preparations.     

Early Warning Signals for Rate-induced Critical Transitions in Salt Marsh Ecosystems

Ecosystems - Intertidal ecosystems are important because of their function as coastal protection and ecological value. Sea level rise may lead to submergence of salt marshes worldwide. Salt marshes...     

Biomechanical warfare in ecology; negative interactions between species by habitat modification

Since the introduction of the term ecosystem engineering by Jones et al. many studies have focused on positive, facilitative interactions caused by ecosystem engineering. Much less emphasis has been placed on the role of ecosystem engineering in causing negative interactions between species. Here, we report on negative interactions between two well known ecosystem engineers occurring at the interface of salt marsh and intertidal flat (i.e. common cordgrass Spartina anglica and lugworms Arenicola marina ), via modification of their joint habitat. A field survey indicated that, although both species share a common habitat, they rarely co-occur on small spatial scales (<1 m). Experiments in the field and in mesocosms reveal that establishment of small Spartina plants is inhibited in Arenicola -dominated patches because of low sediment stability induced by the lugworms. In turn, Arenicola establishment in Spartina -dominated patches is limited by high silt content, compactness and dense rooting of the sediment caused by Spartina presence. Our results show that negative interactions by modification of the environment can result in rapid mutual exclusion, particularly if adverse effects of habitat modification are strong and if both species exhibit positive feedbacks. This illustrates the potential for negative interactions via the environment to affect community composition.     

Multi‐scale habitat modification by coexisting ecosystem engineers drives spatial separation of macrobenthic functional groups

By changing habitat conditions, ecosystem engineers increase niche diversity and have profound effects on the distribution and abundances of other organisms. Although many ecosystems contain several engineering species, it is still unclear how the coexistence of multiple engineers affects the physical habitat and the structure of the community on a landscape scale. Here, we investigated through a large‐scale field manipulation how three coexisting engineers on intertidal flats (cockles Cerastoderma edule; lugworms Arenicola marina; blue mussels Mytilus edulis) influence the functional composition of the local macrobenthic community and what the consequences are at the landscape level. By using biological trait analysis (BTA), we show that on the local scale biogenic changes in sediment accumulation and organic matter content translated into specific shifts in the distribution of functional traits within the community. At a landscape scale, the co‐occurrence of multiple ecosystem engineers resulted in the spatial separation of different functional groups, i.e. different functional groups dominated unique complementary habitats. Our results emphasize the role of co‐occurring multiple engineers in shaping natural communities, thus contributing to a better knowledge of community assembly rules. This understanding can profitably be used to improve ecosystem‐based management and conservation actions.     

Inhibitory effect of IGF-I on induced apoptosis in mouse preimplantation embryos cultured in vitro

Insulin-like growth factor I (IGF-I) has been shown to promote mammalian early embryo development. Increased cell division or decreased cell death have been proposed as two main possible mechanisms in its effect. Here we examine the nature of this promoting effect in a model situation. Camptothecin (0.01 microg/ml) and actimomycin D (0.005 microg/ml) were used to induce apoptosis. Four-cell mouse embryos were cultured in vitro to blastocyst stage in the temporary (15 h) presence or absence of apoptotic inductors and in the permanent presence or absence of IGF-I (100 ng/ml). Embryos were assessed by morphological triple staining (Hoechst 33342, propidium iodide, Calcein AM) and comet assay on Day 5, 120 h after administration of hCG. The number of nuclei, the blastocyst formation, the proportion of embryos containing fragmented DNA and the percentage of apoptotic and secondary necrotic nuclei were assessed. Both inductors of apoptosis significantly increased the percentage of apoptotic and secondary necrotic cells and reduced total cell counts (camptothecin, P>0.001; actinomycin D, P>0.001). When IGF-I was added to the culture medium in the presence of an apoptosis inductor, apoptosis incidence was significantly decreased (P<0.001). The addition of IGF-I into control samples also decreased the percentage of apoptotic and secondary necrotic cells. In contrast, IGF-I addition had no significant influence on embryo development (P>0.05). Our data suggest a primary role for IGF-I as an apoptotic survival factor in mouse preimplantation embryos in specific conditions.     

Isolation and characterization of a large,neurite-associated glycoconjugate from neuroblastoma cells

A high molecular weight glycoconjugate has been isolated from neurite-producing neuronal tumor cells in culture and has been designated as I(0) based on its elution characteristics in gel filtration chromatography. This molecule cannot be found in a variety of nonneuronal cells. I(0) is found in the substratum-attached material or cell fraction of neurite-producing neuroblastoma cells, depending upon culture conditions. It is found in the substratum-bound fraction of B104 rat neuroblastoma cells during serum starvation and in the EGTA-detached cell fraction of B104 cells grown in chemically defined N2 medium. It occurs only in the cell fraction of the human neuroblastoma line Platt. Examination of behavioral variants of the B104 rat line further strengthens the association of I(0) with neurite production; the constitutive neurite-producing E(R)B9 variant contains I(0) while the non-neurite-producing E(R)A11 variant does not. I(0) is large, eluting in the void volume of sepharose-CL2B columns. Radioiodination of intact cells with lactoperoxidase shows I(0) to be a cell surface component. Metabolic radiolabeling studies show that it contains a high proportion of polysaccharide to protein, does not contain mannose, and is unsulfated. Alkaline borohydride reduction release two size classes of large polysaccharide chain. The alkaline reduction results, along with the mannose incorporation studies, show the presence of O-glycosidic linkages and few, if any, N-linkages. Resistance to nitrous acid deamination, insensitivity to glycosaminoglycan lyases, and the absence of sulfation, indicate that I(0) does not contain the glycosaminoglycans hyaluronic acid, chondroitin-, dermatan-, or heparin- sulfates. Affinity column chromatography reveals high binding affinity of I(0) to polyornithine and no binding to gelatin (collagen) or the glycosaminoglycans hyaluronate and heparin. These studies describe a unique high molecular weight glycoconjugate on the surface of neurite-producing neuroblastoma cell lines from two species.