Royal Society Open Science最新文献

This study presents a detailed mathematical analysis of the spatio-temporal dynamics of the RhoA-GEF-H1-myosin signalling network, modelled as a coupled system of reaction-diffusion equations. By employing conservation laws and the quasi-steady state approximation, the dynamics is reduced to a tractable nonlinear system. First, we analyse the temporal system of ordinary differential equations (ODE) in the absence of spatial variation, characterizing stability, bifurcations and oscillatory behaviour through phase-plane analysis and bifurcation theory. As parameter values change, the temporal system transitions between stable dynamics; unstable steady states characterized by oscillatory dynamics; and co-existence between locally stable steady states, or co-existence between a locally stable steady state and a locally stable limit cycle. Second, we extend the analysis to the reaction-diffusion system by incorporating diffusion to the temporal ODE model, leading to a comprehensive study of Turing instabilities and spatial pattern formation. In particular, by adding appropriate diffusion to the temporal model: (i) the uniform steady state can be destabilized leading to the well-known Turing diffusion-driven instability (DDI); (ii) one of the uniform stable steady states in the bistable region can be driven unstable, while the other one remains stable, leading to the formation of travelling wave fronts; and (iii) a stable limit cycle can undergo DDI leading to the formation of spatial patterns. More importantly, the interplay between bistability and diffusion shows how travelling wavefronts can emerge, consistent with experimental observations of cellular contractility pulses. Theoretical results are supported by numerical simulations, providing key insights into the parameter spaces that govern pattern transitions and diffusion-driven instabilities.

Environmental drivers of within-population reproductive patterns are often hypothesized to lead to reproductive strategies tuned to local conditions. Organisms adjust energy allocation between survival and reproduction based on experience, age, lifespan and resource availability. Variation in these energetic investments can be described as different demographic tactics which are expected to optimize the fitness of local populations. These ideas are largely supported by both empirical and model-based studies but research identifying specific strategies and their corresponding environmental drivers within wild populations remains rare. Using 12 years of data, we investigated reproductive investment strategies in a relatively short-lived resident songbird, the mountain chickadee (Poecile gambeli), at two elevations that differ in environmental harshness in the North American Sierra Nevada mountains. Challenging winter environments at high elevations impose strong selection pressure on survival-related traits (e.g. specialized spatial cognition associated with food caching) and significantly shorten the length of the reproductive window. Here, we show that chickadees at a higher elevation lay smaller clutches (ca 0.41 fewer eggs) and produce fewer (ca 0.25 fewer nestlings) but larger offspring (ca 0.4 g heavier) compared to lower elevation residents. Due to the harsher and less predictable environmental conditions at higher elevations, this investment strategy in this resident species likely leads to the production of offspring with greater chances of survival. Overall, our results show that within-species differences in life history strategies may evolve over a small spatial scale along strong environmental gradients.

Here, we report fossil isopods preserved in laminated oil-shale mudstone (dysodile) from the Lower Cretaceous of Lebanon (Lower Barremian, 125 Ma, Grès du Liban Alloformation, Jezzine District). Based on a variety of proxies, their palaeoenvironments are determined to have been a shallow freshwater lake. The fossil isopods were studied using modern imaging techniques, such as multispectral imaging and photometric stereo, allowing for a detailed comparison of these specimens with comparable extant and fossil taxa. The conspecific fossils are herein recognized as remains of a new species-†Dysopodus gezei gen. et sp. nov.-of uncertain affinity within Cymothoida and bearing a strong resemblance to its non-parasitic lineages (Cirolanidae). A conspicuous pleotelson and uropod morphology set it apart from most species, with the notable exception of †Pseudoplakolana chiapaneca gen. nov. et comb. nov. from the Cretaceous of Mexico, originally attributed to an Australasian lineage (herein disputed). So far, the biogeographical distribution of the peri-Mediterranean underground fauna has predominantly been explained through a passive isolation process of former marine species, driven by regressing coastlines. Stemming from a freshwater lake environment, the 125 million-year-old fossils from Lebanon provide an unconventional perspective on the evolutionary origin of extant cave- and groundwater-dwelling cymothoidans.

Sociability, i.e. the tendency to interact with other individuals, varies significantly within populations, with some individuals being consistently more sociable than others. Variation may be maintained because the balance between costs (e.g. increase in aggressive disputes, infection risk) and benefits (e.g. information exchange, cooperation) of sociability varies with the environmental context. At the proximate level, apart from genes, mothers transfer non-genetic compounds to their offspring that can influence the development of social skills. In this context, they may adjust their offspring's sociability to match the social environment they will experience after birth, for example, via prenatal hormones. To test this, we experimentally manipulated the social density as perceived by blue tit females before egg laying. We subsequently measured yolk testosterone concentrations and social interactions among family members post-hatching. Females that were exposed to a simulated high social density transferred less testosterone to their eggs than control females. Network average degree (i.e. the number of social interactions of the brood) was not affected by the social density treatment, but broods with lower yolk testosterone concentrations showed a higher network average degree. This suggests that mothers experiencing an environment with high social density (but not increased resource competition) deposit less yolk testosterone to produce offspring that are probably less aggressive but more sociable.

Evolutionary life history theory predicts that, during development, investment in immunity must be balanced with the demands of growth. How, and at what time scales, this balance is negotiated is unclear. In this study, we examined the potential energetic costs and limitations to cellular immune activity during development, its trade-offs with growth, related sickness behaviour and the role of hypothalamic-pituitary-adrenal (HPA) axis activity in these relationships. We combined biomarker and socio-environmental data on wild juvenile blue monkeys collected over eight months. Rather than detract from energy balance (C-peptide) and growth of lean body mass (creatinine by specific gravity residuals), cellular immune activity (neopterin) increased with energy balance and lean body mass at monthly time scales, suggesting an energetic constraint on cellular immunity. At shorter time scales, higher neopterin diminished subsequent growth. Energetic constraints on immune activity were weakly regulated by HPA activity during low energy states. Our results suggest that cellular immune activity is both costly and limited by physical condition in wild developing primates.

Tropical coral reefs are dynamic, disturbance-driven ecosystems that are heterogeneous across space and time, partly owing to gradients in cross-scale human impacts and natural environmental factors. Localized management interventions that strive to maintain the long-term persistence and function of coral reefs need to be informed by how and why reef habitats vary. Using the 'multivariate dispersion' metric, a statistical approach to measure ecological community variability, we quantified spatial gradients in coral reef benthic communities around Tutuila Island in American Samoa, central South Pacific. Benthic communities with low, medium and high dispersion each had distinct and consistent underlying benthic community characteristics. Low dispersion sites were consistently characterized by high hard coral cover, medium dispersion sites were generally dominated by crustose coralline algae, while high dispersion sites were dominated by turf and fleshy coralline algae. Variability in hard coral and turf algal cover explained 42% of the underlying variation in benthic community dispersion across sites, while site-level gradients in human impacts and environmental factors did not correlate well with variations in benthic community dispersion. The metric should be further tested on temporal data to determine whether it can summarize complex community changes in response to and following acute disturbance.

Host diversity can affect parasite prevalence, a phenomenon widely studied in macroscopic organisms. However, data from microscopic communities are lacking, despite their essential role in ecosystem functioning and the unique experimental opportunities microscopic organisms offer. Here, we study diversity-disease effects in wild nematode communities by profiting from the molecular tools available in the well-studied model nematode Caenorhabditis elegans. Nanopore sequencing was used to characterize nematode community diversity and composition, whereas parasites were identified using nine distinct experimental assays based on fluorescent staining or fluorescent reporter strains. Our results indicate that biotic stress is abundant in wild nematode communities. Moreover, in two assays, diversity-disease relations were observed: microsporidia and immune system activation were more often detected in relatively species-poor communities. Other assays, targeting different parasites, were without diversity-disease relations. Together, this study provides the first demonstration of diversity-disease effects in microbial communities and establishes the use of nematode communities as model systems to study disease-diversity relationships.

In this report, a structurally unique phenothiazine (PTZ) core is linked with glutamic acid-based dendrons through a solid-phase peptide synthesis approach to access a variety of PTZ-linked dendrons conveniently. Inferior cytotoxicity of anionic surface-linked second-generation glutamic acid-based dendrons would be more desirable for various applications than respective lysine-based dendrons. Solid-phase synthesis of PTZ-linked glutamic acid-based dendrons would be a novel approach to access this class of molecules. These newly synthesized dendrons were screened as an inhibitor against the main protease (M^pro) enzyme, proposed to be the best target against SARS-CoV-2. The preliminary assay studies designated a moderate response for the M^pro inhibition, specifically by tryptophan (Trp)-enriched dendron, among other analogues, which play a vital role in combating COVID-19. Further, the experimental studies realize the essential contribution of the PTZ core in interacting with the M^pro enzyme. Molecular dynamics (MD) simulations revealed that the active dendrons formed stable complexes with M^pro, and the binding affinity of the Trp-based PTZ-linked dendrons was higher than that of the decoy dendron analogue.

Agricultural biomass production in China is substantial, and the densification pretreatment of agricultural biomass has the potential to reduce usage costs and increase fuel energy density. However, there is still uncertainty regarding the impact of densification pretreatment on combustion characteristics and particulate matter emissions. In this study, the combustion characteristics of raw biomass and biomass pellets were investigated using a thermogravimetric analyser and fixed-bed reactor with cotton stalk and rice husk. The findings indicate that biomass densification pretreatment enhances combustion performance, resulting in more concentrated and intense combustion compared with untreated biomass. The combustion models become more intricate due to the process of densification pretreatment. For cotton stalk, densification pretreatment proves beneficial in reducing the emission of PM_0.1-10 (particulate matter with a diameter between 0.1 and 10 µm), although it does not exhibit a discernible inhibitory effect on ultrafine particles (<0.1 μm). Densification pretreatment has also been shown to suppress the conversion of alkali metal sulfides into particulate matter. In the case of rice husk, densification pretreatment primarily reduces PM_1-10 emissions while simultaneously increasing the formation of fine particles (<1 μm). This process facilitates the interaction between Si and alkali metal chlorides, thereby enhancing silicate reaction and impeding the conversion of alkali metal chlorides into PM₁. However, the impact of densification pretreatment on the elemental composition of PM_1-10 remains insignificant in both biomass samples.

Human muscles exhibit great versatility, not only generating forces for demanding athleticism, but also for fine motor tasks. While standard musculoskeletal models may reproduce this versatility, they often lack multiple motor units (MUs) and rate-coded control. To investigate how these features affect a muscle's ability to generate desired force profiles, we performed simulations with nine alternative MU pool models for two cases: (i) a tibialis anterior muscle generating an isometric trapezoidal force profile, and (ii) a generic shoulder muscle generating force for a reaching movement whilst undergoing predetermined length changes. We implemented two control strategies, pure feedforward and combined feedforward-feedback, each parameterized using elementary tasks. The results suggest that the characteristics of MU pools have relatively little impact on the pools' overall ability to match forces across all tasks, although performances for individual tasks varied. Feedback improved performance for nearly all MU pools and tasks, but the physiologically more relevant MU pool types were more responsive to feedback particularly during reaching. While all MU pool models performed well in the conditions tested, we highlight the need to consider the functional characteristics of the control of rate-coded MU pools given the vast repertoire of dynamic tasks performed by muscles.