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  1. Abstract

    The global population urgently requires alternative food sources that provide the micronutrient-rich profile of meat and fish but with lower environmental cost. We present a solution in the form of ‘Naked Clams’ (teredinids/shipworms) - a seldom researched group of bivalves, that feature tiny shells and live in and feed on wood, turning it into protein and essential nutrients. We report the first pilot system for Naked Clam aquaculture, the first nutritional profile and feeding efficacy assessment, and demonstrate value offered by microencapsulated feeds in fortifying Naked Clams. Naked Clams were rich in nutrients including vitamin B12and monounsaturated fatty acids, and shared the high protein content of conventional bivalves such as blue mussels (Mytilus edulis). Microencapsulated algal feeds enriched the Naked Clams with essential PUFAs including EPA and DHA, with potential for further tailoring. Additional work is required, but this study represents a gateway to a new form of sustainable food production.

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  2. Abstract

    The soil amoebaDictyostelium discoideumacts as both a predator and potential host for diverse bacteria. We tested fifteenPseudomonasstrains that were isolated from transiently infected wildD. discoideumfor ability to escape predation and infectD. discoideumfruiting bodies. Three predation-resistant strains frequently caused extracellular infections of fruiting bodies but were not found within spores. Furthermore, infection by one of these species induces secondary infections and suppresses predation of otherwise edible bacteria. Another strain can persist inside of amoebae after being phagocytosed but is rarely taken up. We sequenced isolate genomes and discovered that predation-resistant isolates are not monophyletic. ManyPseudomonasisolates encode secretion systems and toxins known to improve resistance to phagocytosis in other species, as well as diverse secondary metabolite biosynthetic gene clusters that may contribute to predation resistance. However, the distribution of these genes alone cannot explain why some strains are edible and others are not. Each lineage may employ a unique mechanism for resistance.

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  3. Abstract

    Establishment of extant terrestrial vertebrate faunas in North America was influenced by a set of factors associated with temporal changes in climate and ecology that operated at different geographic scales. While the biogeography of extant taxa can be inferred from phylogenies, these omit lineages that have gone regionally extinct and for which the only direct evidence is the fossil record. A comprehensive study of anurans from the Late Oligocene of Florida reveals an abundance of fossils referred to Eleutherodactylus. Time-calibrated molecular phylogenies have suggested that this genus originated in the Caribbean in the Early Oligocene and then colonized Central America in the Middle Miocene. Here, we describe the first records of pre-Quaternary fossils referred to Eleutherodactylus from Florida. Results from analysis of inter- and intraspecific variation in anatomy, size, and shape of isolated bones of fossil and extant species suggest that the fossils represent adult individuals with an estimated body size (snout–urostyle length) of 16.8–29.8 mm. We show that Eleutherodactylus was established by the Late Oligocene in North America well before colonizing Central America in the Miocene. We provide, for the first time, evidence of dispersal of amphibians from the Caribbean into North America during the Late Oligocene.

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  4. Free, publicly-accessible full text available August 1, 2024

    In star-forming clouds, high velocity flow gives rise to large fluctuations of density. In this work, we explore the correlation between velocity magnitude (speed) and density. We develop an analytic formula for the joint probability distribution function (PDF) of density and speed, and discuss its properties. In order to develop an accurate model for the joint PDF, we first develop improved models of the marginalized distributions of density and speed. We confront our results with a suite of 12 supersonic isothermal simulations with resolution of $1024^3$ cells in which the turbulence is driven by 3 different forcing modes (solenoidal, mixed, and compressive) and 4 rms Mach numbers (1, 2, 4, 8). We show, that for transsonic turbulence, density and speed are correlated to a considerable degree and the simple assumption of independence fails to accurately describe their statistics. In the supersonic regime, the correlations tend to weaken with growing Mach number. Our new model of the joint and marginalized PDFs are a factor of 3 better than uncorrelated, and provides insight into this important process.

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  6. A miniature optical-sectioning fluorescence microscope with high sensitivity and resolution would enable non-invasive and real-time tissue inspection, with potential use cases including early disease detection and intraoperative guidance. Previously, we developed a miniature MEMS-based dual-axis confocal (DAC) microscope that enabled video-rate optically sectionedin vivomicroscopy of human tissues. However, the device’s clinical utility was limited due to a small field of view, a non-adjustable working distance, and a lack of a sterilization strategy. In our latest design, we have made improvements to achieve a 2x increase in the field of view (600 × 300 µm) and an adjustable working distance range of 150 µm over a wide range of excitation/emission wavelengths (488–750 nm), all while maintaining a high frame rate of 15 frames per second (fps). Furthermore, the device is designed to image through a disposable sterile plastic drape for convenient clinical use. We rigorously characterize the performance of the device and show example images ofex vivotissues to demonstrate the optical performance of our new design, including fixed mouse skin and human prostate, as well as fresh mouse kidney, mouse intestine, and human head and neck surgical specimens with corresponding H&E histology. These improvements will facilitate clinical testing and translation.

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  7. Abstract As we contemplate the future of forest landscapes under changing climate conditions and land‐use demands, there is increasing value in studying historic forest conditions and how these landscapes have changed following past disturbances. Historic landscape paintings are a potential source of data on preindustrial forests with highly detailed, full‐color depictions of overstory and understory environments. They display key details about forest community composition, microhabitat features, and structural complexity from a time well before the advent of color photography. Despite these paintings' potential, their scientific applications have been impeded by questions of validity. How truly accurate are the images portrayed in these paintings? How much of an image is an artist's manipulation of a scene to best illustrate an allegory or romanticized view of nature? Following an established assessment model from historical ecology for evaluating resource validity, we demonstrate how scholarship on art history can be integrated with ecological understanding of forest landscapes to follow this model and address these questions of image veracity in 19th century American art. Further, to illustrate the potential use of these historic images in ecological studies, we present in a case study assessing microhabitat features of 10 different paintings. While this paper explores 19th century landscape art broadly, we focus our art historical review in particular on Asher Durand, a prolific and influential artist associated with the so‐called “Hudson River School” in the mid‐1800s. Durand left clear records about his perspectives on accurately depicting nature, and from a review of images and writings of Durand, we find support for the potential use of many of his paintings and sketches in historic forest ecology research. However, we also identify important caveats regarding potential ecological interpretations from these images. More broadly, because 19th century landscape paintings are not always directly transcriptive, and because regional art cultures differed in the 1800s, we cannot within this paper speak about landscape image veracity across all 19th century landscape art. However, in following established methods in historical ecology and integrating tools from art history research, we show that one can identify accurate historic landscape paintings for application in scientific studies. 
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    Free, publicly-accessible full text available September 1, 2024
  8. Abstract

    A companion paper by Fritts et al. reviews evidence for Kelvin–Helmholtz instability (KHI) “tube” and “knot” (T&K) dynamics that appear to be widespread throughout the atmosphere. Here we describe the results of an idealized direct numerical simulation of multiscale gravity wave dynamics that reveals multiple larger- and smaller-scale KHI T&K events. The results enable assessments of the environments in which these dynamics arise and their competition with concurrent gravity wave breaking in driving turbulence and energy dissipation. A larger-scale event is diagnosed in detail and reveals diverse and intense T&K dynamics driving more intense turbulence than occurs due to gravity wave breaking in the same environment. Smaller-scale events reveal that KHI T&K dynamics readily extend to weaker, smaller-scale, and increasingly viscous shear flows. Our results suggest that KHI T&K dynamics should be widespread, perhaps ubiquitous, wherever superposed gravity waves induce intensifying shear layers, because such layers are virtually always present. A second companion paper demonstrates that KHI T&K dynamics exhibit elevated turbulence generation and energy dissipation rates extending to smaller Reynolds numbers for relevant KHI scales wherever they arise. These dynamics are suggested to be significant sources of turbulence and mixing throughout the atmosphere that are currently ignored or underrepresented in turbulence parameterizations in regional and global models.

    Significance Statement

    Atmospheric observations reveal that Kelvin–Helmholtz instabilities (KHI) often exhibit complex interactions described as “tube” and “knot” (T&K) dynamics in the presence of larger-scale gravity waves (GWs). These dynamics may prove to make significant contributions to energy dissipation and mixing that are not presently accounted for in large-scale modeling and weather prediction. We explore here the occurrence of KHI T&K dynamics in an idealized model that describes their behavior and character arising at larger and smaller scales due to superposed, large-amplitude GWs. The results reveal that KHI T&K dynamics arise at larger and smaller scales, and that their turbulence intensities can be comparable to those of the GWs.

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  9. The social amoeba Dictyostelium discoideum engages in a complex relationship with bacterial endosymbionts in the genus Paraburkholderia, which can benefit their host by imbuing it with the ability to carry prey bacteria throughout its life cycle. The relationship between D. discoideum and Paraburkholderia has been shown to take place across many strains and a large geographical area, but little is known about Paraburkholderia’s potential interaction with other dictyostelid species. We explore the ability of three Paraburkholderia species to stably infect and induce bacterial carriage in other dictyostelid hosts. We found that all three Paraburkholderia species successfully infected and induced carriage in seven species of Dictyostelium hosts. While the overall behaviour was qualitatively similar to that previously observed in infections of D. discoideum, differences in the outcomes of different host/symbiont combinations suggest a degree of specialization between partners. Paraburkholderia was unable to maintain a stable association with the more distantly related host Polysphondylium violaceum. Our results suggest that the mechanisms and evolutionary history of Paraburkholderia’s symbiotic relationships may be general within Dictyostelium hosts, but not so general that it can associate with hosts of other genera. Our work further develops an emerging model system for the study of symbiosis in microbes. 
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    Free, publicly-accessible full text available July 19, 2024
  10. Some endosymbionts living within a host must modulate their hosts’ immune systems in order to infect and persist. We studied the effect of a bacterial endosymbiont on a facultatively multicellular social amoeba host. Aggregates of the amoeba Dictyostelium discoideum contain a subpopulation of sentinel cells that function akin to the immune systems of more conventional multicellular organisms. Sentinel cells sequester and discard toxins from D. discoideum aggregates and may play a central role in defence against pathogens. We measured the number and functionality of sentinel cells in aggregates of D. discoideum infected by bacterial endosymbionts in the genus Paraburkholderia. Infected D. discoideum produced fewer and less functional sentinel cells, suggesting that Paraburkholderia may interfere with its host’s immune system. Despite impaired sentinel cells, however, infected D. discoideum were less sensitive to ethidium bromide toxicity, suggesting that Paraburkholderia may also have a protective effect on its host. By contrast, D. discoideum infected by Paraburkholderia did not show differences in their sensitivity to two non-symbiotic pathogens. Our results expand previous work on yet another aspect of the complicated relationship between D. discoideum and Paraburkholderia, which has considerable potential as a model for the study of symbiosis. 
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    Free, publicly-accessible full text available August 1, 2024