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Animals can cope with dehydration in a myriad of ways, both behaviorally and physiologically. The oxidation of protein produces more metabolic water per kJ than that of fat or carbohydrate, and it is well established that birds increase protein catabolism in response to high rates of water loss. However, the fate of amino acids mobilized in response to water restriction has not been explicitly determined. While protein catabolism releases bound water, we hypothesized that water restricted birds would also oxidize the resulting amino acids, producing additional water as a product of oxidative phosphorylation. To test this, we fed captive house sparrows (Passer domesticus) 13C-labeled leucine for 9 weeks to label endogenous proteins. We conducted weekly trials during which we measured the physiological response to water restriction as changes in lean mass, fat mass, metabolism, and the enrichment of 13C in exhaled CO2. If water restricted birds catabolized proteins and oxidized the resulting amino acids, we expected to simultaneously observe greater lean mass losses and elevated δ13Cbreath relative to control birds. We found that water restricted birds catabolized more lean tissue and also had enriched 13Cbreath in response to water restriction, supporting our hypothesis. δ13Cbreath, however, varied with metabolic rate and the length of the water restriction period, suggesting that birds may spare protein when water balance can be achieved using other physiological strategies.

 

The rediscovery of diatom blooms embedded within and beneath the Lake Erie ice cover (2007–2012) ignited interest in psychrophilic adaptations and winter limnology. Subsequent studies determined the vital role ice plays in winter diatom ecophysiology as diatoms partition to the underside of ice, thereby fixing their location within the photic zone. Yet, climate change has led to widespread ice decline across the Great Lakes, with Lake Erie presenting a nearly “ice-free” state in several recent winters. It has been hypothesized that the resultant turbid, isothermal water column induces light limitation amongst winter diatoms and thus serves as a competitive disadvantage. To investigate this hypothesis, we conducted a physiochemical and metatranscriptomic survey that spanned spatial, temporal, and climatic gradients of the winter Lake Erie water column (2019–2020). Our results suggest that ice-free conditions decreased planktonic diatom bloom magnitude and altered diatom community composition. Diatoms increased their expression of various photosynthetic genes and iron transporters, which suggests that the diatoms are attempting to increase their quantity of photosystems and light-harvesting components (a well-defined indicator of light limitation). We identified two gene families which serve to increase diatom fitness in the turbid ice-free water column: proton-pumping rhodopsins (a potential second means of light-driven energy acquisition) and fasciclins (a means to “raft” together to increase buoyancy and co-locate to the surface to optimize light acquisition). With large-scale climatic changes already underway, our observations provide insight into how diatoms respond to the dynamic ice conditions of today and shed light on how they will fare in a climatically altered tomorrow.

 

This work is a comparative genomics investigation of the aromatic and xenobiotic compound degradation capabilities and heavy metal resistance of environmental bacterial isolates previously identified by our lab, Achromobacter xylosoxidans ADAF13, Exiguobacterium sp. KKBO11, Ochrobactrum anthropi FRAF13, Pseudomonas putida CBF10-2, Pseudomonas stutzeri ODKF13, Rhizobium radiobacter GHKF11, and Stenotrophomonas maltophilia CBF10-1. This work sought to assess the potential of these isolates as bioremediation tools. We found a variety of aromatic degradation pathways though none directly acts on industrial compounds such as polycyclic aromatic compounds, benzene, phthalate, or xylene. Achromobacter xylosoxidans ADAF13, P. putida CBF10-2, and P. stutzeri ODKF13 showed the most complete pathways for aromatic compound degradation and halobenzoate degradation. All isolates contained heavy metal resistance genes for arsenic, cadmium, copper, chromium, lead, mercury, and zinc. Arsenic resistance genes were the most common among isolates and were organized into structurally diverse ars operons. Collectively, our data indicated that A. xylosoxidans ADAF13, P. putida CBF10-2, and P. stutzeri ODKF13 are strong candidates for further enhancement and development as bioremediation tools. 

We revisit computationally relaxed locally decodable codes (crLDCs) (Blocki et al., Trans. Inf. Theory ’21) and give two new constructions. Our first construction is a Hamming crLDC that is conceptually simpler than prior constructions, leveraging digital signature schemes and an appropriately chosen Hamming code. Our second construction is an extension of our Hamming crLDC to handle insertion-deletion (InsDel) errors, yielding an InsDel crLDC. This extension crucially relies on the noisy binary search techniques of Block et al. (FSTTCS ’20) to handle InsDel errors. Both crLDC constructions have binary codeword alphabets, are resilient to a constant fraction of Hamming and InsDel errors, respectively, and under suitable parameter choices have poly-logarithmic locality and encoding length linear in the message length and polynomial in the security parameter. These parameters compare favorably to prior constructions in the poly-logarithmic locality regime. 

Patterns of morphological divergence across species’ ranges can provide insight into local adaptation and speciation. In this study, we compared phenotypic divergence among 4,221 crickets from 337 populations of two closely related species of field cricket,Gryllus firmusandG. pennsylvanicus, and their hybrids. We found that these species differ across their geographic range in key morphological traits, such as body size and ovipositor length, and we directly compared phenotype with genotype for a subset of crickets to demonstrate nuclear genetic introgression, phenotypic intermediacy of hybrids, and essentially unidirectional mitochondrial introgression. We discuss how these morphological traits relate to life history differences between the two species. Our comparisons across geographic areas support prior research suggesting that cryptic variation withinG. firmusmay represent different species. Our study highlights how variable morphology can be across wide-ranging species and the importance of studying reproductive barriers in more than one or two transects of a hybrid zone.

 

Subaqueous vortex ripples in equilibrium are characterized by their unique geometry and dimensions. Motivated by the recent direct numerical simulation study of oscillatory turbulent flow over a wavy bottom by Önder & Yuan ( J. Fluid Mech. , vol. 858, 2019, pp. 264–314), the objective of this study is to further investigate the fluid dynamical controls that determine the distinctive equilibrium dimensions of vortex ripples. We use direct numerical simulations to investigate the differences in flow kinetics between sinusoidal oscillatory flow over equilibrium and out-of-equilibrium vortex ripples. In comparison with the equilibrium case, the spanwise coherent vortices, the averaged bottom shear stress on overlying flow and the shear stress distribution on the ripple surface are identified as the key fluid dynamical controls on equilibrium dimensions. Based on these controls, we propose mechanisms in the selection of vortex ripple dimensions. We observe that the flow adjusts in such a way that the interaction between overlying flow and vortex ripples tends to generate the strongest coherent vortices while the ripple surface (or overlying flow) experiences the smallest shear stress averaged over ripple wavelength during the selection process. Through a triple decomposition of the flow, the component of the ripple-induced fluctuation is found to dictate these fluid dynamical controls, which implies that this component plays an important role in the evolution of vortex ripples.