5,014 research outputs found

    Acute Lymphatic Filariasis Infection in United States armed forces personnel deployed to the Pacific area of operations during World War II provides important lessons for today

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    The deployment of United States (US) Armed Forces personnel into the central Pacific islands of Samoa and Tonga, which is highly-endemic for lymphatic filariasis (LF), resulted in thousands of cases of the acute form of this disease and greatly reduced their ability to carry out their mission. The major driving factor for the intensity of transmission was the aggressiveness and efficiency of the Aedes species mosquito vectors, especially the day-biting Ae. Polynesiensis. The paper reminds us of the danger that tropical diseases can pose for troops sent into endemic areas and constant and careful surveillance that is required to prevent rapid resurgence of Aedes-transmitted LF in populations, where the LF elimination program has been successful

    Marine heatwave hotspots in coral reef environments: physical drivers, ecophysiological outcomes and impact upon structural complexity

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    A changing climate is driving increasingly common and prolonged marine heatwaves (MHWs) and these extreme events have now been widely documented to severely impact marine ecosystems globally. However MHWs have rarely recently been considered when examining temperature-induced degradation of coral reef ecosystems. Here we consider extreme, localised thermal anomalies, nested within broader increases in sea surface temperature, which fulfil the definitive criteria for MHWs. These acute and intense events, referred to here as MHW hotspots, are not always well represented in the current framework used to describe coral bleaching, but do have distinct ecological outcomes, including widespread bleaching and rapid mass mortality of putatively thermally tolerant coral species. The physical drivers of these localised hotspots are discussed here, and in doing so we present a comprehensive theoretical framework that links the biological responses of the coral photo-endosymbiotic organism to extreme thermal stress and ecological changes on reefs associated after MHW hotspots. We describe how the rapid onset of high temperatures drives immediate heat-stress induced cellular damage, overwhelming mechanisms that would otherwise mitigate the impact of gradually accumulated thermal stress. The warm environment, and increased light penetration of the coral skeleton due to the loss of coral tissues, coupled with coral tissue decay support rapid microbial growth in the skeletal microenvironment, resulting in the widely unrecognised consequence of rapid decay and degeneration of the coral skeletons. This accelerated degeneration of the coral skeletonson a reef scale hinder the recovery of coral populations and increase the likelihood of phase shifts towards algal dominance. We suggest that MHW hotspots, through driving rapid heat-induced mortality, compromise reefs' structural frameworks to the detriment of long term recovery. We propose that MHW hotspots be considered as a distinct class of thermal stress events in coral reefs, and that the current framework used to describe coral bleaching and mass mortality be expanded to include these. We urge further research into how coral mortality affects bioerosion by coral endoliths

    A Comparative Analysis of Microbial DNA Preparation Methods for Use With Massive and Branching Coral Growth Forms

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    In the last two decades, over 100 studies have investigated the structure of the coral microbiome. However, as yet there are no standardized methods applied to sample preservation and preparation, with different studies using distinct methods. There have also been several comparisons made of microbiome data generated across different studies, which have not addressed the influence of the methodology employed over each of the microbiome datasets. Here, we assess three different preservation methods; salt saturated dimethyl sulfoxide (DMSO) – EDTA, snap freezing with liquid nitrogen and 4% paraformaldehyde solution, and two different preparation methodologies; bead beating and crushing, that have been applied to study the coral microbiome. We compare the resultant bacterial assemblage data for two coral growth forms, the massive coral Goniastrea edwardsi and the branching coral Isopora palifera. We show that microbiome datasets generated from differing preservation and processing protocols are comparable in composition (presence/absence). Significant discrepancies between preservation and homogenization methods are observed in structure (relative abundance), and in the occurrence and dominance of taxa, with rare (low abundance and low occurrence) phylotypes being the most variable fraction of the microbial community. Finally, we provide evidence to support chemical preservation with DMSO as effective as snap freezing samples for generating reliable and robust microbiome datasets. In conclusion, we recommend where possible a standardized preservation and extraction method be taken up by the field to provide the best possible practices for detailed assessments of symbiotic and conserved bacterial associations

    Differential Responses of the Coral Host and Their Algal Symbiont to Thermal Stress

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    The success of any symbiosis under stress conditions is dependent upon the responses of both partners to that stress. The coral symbiosis is particularly susceptible to small increases of temperature above the long term summer maxima, which leads to the phenomenon known as coral bleaching, where the intracellular dinoflagellate symbionts are expelled. Here we for the first time used quantitative PCR to simultaneously examine the gene expression response of orthologs of the coral Acropora aspera and their dinoflagellate symbiont Symbiodinium. During an experimental bleaching event significant up-regulation of genes involved in stress response (HSP90 and HSP70) and carbon metabolism (glyceraldehyde-3-phosphate dehydrogenase, α-ketoglutarate dehydrogenase, glycogen synthase and glycogen phosphorylase) from the coral host were observed. In contrast in the symbiont, HSP90 expression decreased, while HSP70 levels were increased on only one day, and only the α-ketoglutarate dehydrogenase expression levels were found to increase. In addition the changes seen in expression patterns of the coral host were much larger, up to 10.5 fold, compared to the symbiont response, which in all cases was less than 2-fold. This targeted study of the expression of key metabolic and stress genes demonstrates that the response of the coral and their symbiont vary significantly, also a response in the host transcriptome was observed prior to what has previously been thought to be the temperatures at which thermal stress events occur

    High flow conditions mediate damaging impacts of sub-lethal thermal stress on corals' endosymbiotic algae

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    The effects of thermal anomalies on tropical coral endosymbiosis can be mediated by a range of environmental factors, which in turn ultimately influence coral health and survival. One such factor is the water flow conditions over coral reefs and corals. Although the physiological benefits of living under high water flow are well known, there remains a lack of conclusive experimental evidence characterizing how flow mitigates thermal stress responses in corals. Here we use in situ measurements of flow in a variety of reef habitats to constrain the importance of flow speeds on the endosymbiosis of an important reef building species under different thermal regimes. Under high flow speeds (0.15 m s−1) and thermal stress, coral endosymbionts retained photosynthetic function and recovery capacity for longer compared to low flow conditions (0.03 m s−1). We hypothesize that this may be due to increased rates of mass transfer of key metabolites under higher flow, putatively allowing corals to maintain photosynthetic efficiency for longer. We also identified a positive interactive effect between high flow and a pre-stress, sub-lethal pulse in temperature. While higher flow may delay the onset of photosynthetic stress, it does not appear to confer long-term protection; sustained exposure to thermal stress (eDHW accumulation equivalent to 4.9°C weeks) eventually overwhelmed the coral meta-organism as evidenced by eventual declines in photo-physiological function and endosymbiont densities. Investigating flow patterns at the scale of metres within the context of these physiological impacts can reveal interesting avenues for coral reef management. This study increases our understanding of the effects of water flow on coral reef health in an era of climate change and highlights the potential to learn from existing beneficial bio-physical interactions for the effective preservation of coral reefs into the future

    Exact solutions for the wrinkle patterns of confined elastic shells

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    Thin elastic membranes form complex wrinkle patterns when put on substrates of different shapes. Such patterns continue to receive attention across science and engineering. This is due, in part, to the promise of lithography-free micropatterning, but also to the observation that similar patterns arise in biological systems from growth. The challenge is to explain the patterns in any given setup, even when they fail to be robust. Building on the theoretical foundation of [Tobasco, to appear in Arch. Ration. Mech. Anal., arXiv:1906.02153], we derive a complete and simple rule set for wrinkles in the model system of a curved shell on a liquid bath. Our rules apply to shells whose initial Gaussian curvatures are of one sign, such as cutouts of saddles and spheres. They predict the surprising coexistence of orderly wrinkles alongside disordered regions where the response appears stochastic, which we confirm in experiment and simulation. They also unveil the role of the shell's medial axis, a distinguished locus of points that we show is a basic driver in pattern selection. Finally, they explain how the sign of the shell's initial curvature dictates the presence or lack of disorder. Armed with our simple rules, and the methodology underlying them, one can anticipate the creation of designer wrinkle patterns.Comment: Extended text including Supplementary Information. Heavily revised to focus the exposition and incorporate new results; title chang

    Intestinal Microbiome Richness of Coral Reef Damselfishes (Actinopterygii: Pomacentridae)

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    Fish gastro-intestinal system harbors diverse microbiomes that affect the host's digestion, nutrition, and immunity. Despite the great taxonomic diversity of fish, little is understood about fish microbiome and the factors that determine its structure and composition. Damselfish are important coral reef species that play pivotal roles in determining algae and coral population structures of reefs. Broadly, damselfish belong to either of two trophic guilds based on whether they are planktivorous or algae-farming. In this study, we used 16S rRNA gene sequencing to investigate the intestinal microbiome of 5 planktivorous and 5 algae-farming damselfish species (Pomacentridae) from the Great Barrier Reef. We detected Gammaproteobacteria ASVs belonging to the genus Actinobacillus in 80% of sampled individuals across the 2 trophic guilds, thus, bacteria in this genus can be considered possible core members of pomacentrid microbiomes. Algae-farming damselfish had greater bacterial alpha-diversity, a more diverse core microbiome and shared 35 ± 22 ASVs, whereas planktivorous species shared 7 ± 3 ASVs. Our data also highlight differences in microbiomes associated with both trophic guilds. For instance, algae-farming damselfish were enriched in Pasteurellaceae, whilst planktivorous damselfish in Vibrionaceae. Finally, we show shifts in bacterial community composition along the intestines. ASVs associated with the classes Bacteroidia, Clostridia, and Mollicutes bacteria were predominant in the anterior intestinal regions while Gammaproteobacteria abundance was higher in the stomach. Our results suggest that the richness of the intestinal bacterial communities of damselfish reflects host species diet and trophic guild

    Rebuilding relationships on coral reefs: Coral bleaching knowledge-sharing to aid adaptation planning for reef users: Bleaching emergence on reefs demonstrates the need to consider reef scale and accessibility when preparing for, and responding to, coral bleaching

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    Coral bleaching has impacted reefs worldwide and the predictions of near-annual bleaching from over two decades ago have now been realized. While technology currently provides the means to predict large-scale bleaching, predicting reef-scale and within-reef patterns in real-time for all reef users is limited. In 2020, heat stress across the Great Barrier Reef underpinned the region's third bleaching event in 5 years. Here we review the heterogeneous emergence of bleaching across Heron Island reef habitats and discuss the oceanographic drivers that underpinned variable bleaching emergence. We do so as a case study to highlight how reef end-user groups who engage with coral reefs in different ways require targeted guidance for how, and when, to alter their use of coral reefs in response to bleaching events. Our case study of coral bleaching emergence demonstrates how within-reef scale nowcasting of coral bleaching could aid the development of accessible and equitable bleaching response strategies on coral reefs. Also see the video abstract here: https://youtu.be/N9Tgb8N-vN0

    Understanding decay in marine calcifiers: Micro-CT analysis of skeletal structures provides insight into the impacts of a changing climate in marine ecosystems

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    Calcifying organisms and their exoskeletons support some of the most diverse and economically important ecosystems in our oceans. Under a changing climate, we are beginning to see alterations to the structure and properties of these exoskeletons due to ocean acidification, warming and accelerated rates of bioerosion. Our understanding has grown as a result of using micro‐computed tomography (μCT) but its applications in marine biology have not taken full advantage of the technological development in this methodology. We present a significant advancement in the use of this method to studying decalcification in a marine calcifier. We present a detailed workflow on best practice for μCT image processing and analysis of marine calcifiers, designed using coral skeletons subjected to acute, short‐term microbial bioerosion. This includes estimating subresolution microporosity and describing pore space morphological characteristics of macroporosity, in perforate and imperforate exoskeletons. These metrics are compared between control and bieroded samples, and are correlated with skeletal hardness as measured by nanoindentation. Our results suggest that using subresolution microporosity analysis improves the spatiotemporal resolution of μCT data and can detect changes not seen in macroporosity, in both perforate and imperforate skeletons. In imperforate samples, the mean size and relative number of pores in the macroporous portion of the images changed significantly where total macroporosity did not. The increased number of pores and higher microporosity are both directly related to a physical weakening of the calcareous exoskeletons of imperforate corals only. In perforate corals, increased macroporosity was accompanied by an overall widening of pore spaces though this did not correlate with sample hardness. These novel techniques complement traditional approaches and in combination demonstrate the potential for using μCT scanning to sensitively track the process of decalcification from a structural and morphological perspective. Importantly, these approaches do not necessarily rely on ultra‐high resolution (i.e. single micron) scans and so maintain the accessibility of this technology. The continued optimization of these tools for a variety of marine calcifiers will advance our understanding of the effect of climate change on marine biogenic calcified structures.Australian Research Council, Grant/Award Number: DP180103199; International Coral Reef Societ

    Recombinant MVA-prime elicits neutralizing antibody responses by inducing antigen-specific B cells in the germinal center.

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    The RV144 HIV-1 vaccine trial has been the only clinical trial to date that has shown any degree of efficacy and associated with the presence of vaccine-elicited HIV-1 envelope-specific binding antibody and CD4+ T-cell responses. This trial also showed that a vector-prime protein boost combined vaccine strategy was better than when used alone. Here we have studied three different priming vectors-plasmid DNA, recombinant MVA, and recombinant VSV, all encoding clade C transmitted/founder Env 1086 C gp140, for priming three groups of six non-human primates each, followed by a protein boost with adjuvanted 1086 C gp120 protein. Our data showed that MVA-priming favors the development of higher antibody binding titers and neutralizing activity compared with other vectors. Analyses of the draining lymph nodes revealed that MVA-prime induced increased germinal center reactivity characterized by higher frequencies of germinal center (PNA <sup>hi</sup> ) B cells, higher frequencies of antigen-specific B-cell responses as well as an increased frequency of the highly differentiated (ICOS <sup>hi</sup> CD150 <sup>lo</sup> ) Tfh-cell subset
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