Strong Response Research Articles

Trypanosoma cruzi interaction with host tissues modulate the composition of large extracellular vesicles

Trypanosoma cruzi is the protozoan that causes Chagas disease (CD), an endemic parasitosis in Latin America distributed around the globe. If CD is not treated in acute phase, the parasite remains silent for years in the host's tissues in a chronic form, which may progress to cardiac, digestive or neurological manifestations. Recently, studies indicated that the gastrointestinal tract represents an important reservoir for T. cruzi in the chronic phase. During interaction T. cruzi and host cells release extracellular vesicles (EVs) that modulates the immune system and infection, but the dynamics of secretion of host and parasite molecules through these EVs is not understood. Now, we used two cell lines: mouse myoblast cell line C2C12, and human intestinal epithelial cell line Caco-2to simulate the environments found by the parasite in the host. We isolated large EVs (LEVs) from the interaction of T. cruzi CL Brener and Dm28c/C2C12 and Caco-2 cells upon 2 and 24 h of infection. Our data showed that at two hours there is a strong cellular response mediated by EVs, both in the number, variety and enrichment/targeting of proteins found in LEVs for diverse functions. Qualitative and quantitative analysis showed that proteins exported in LEVs of C2C12 and Caco-2 have different patterns. We found a predominance of host proteins at early infection. The parasite-host cell interaction induces a switch in the functionality of proteins carried by LEVs and a heterogeneous response depending on the tissues analyzed. Protein–protein interaction analysis showed that cytoplasmic and mitochondrial homologues of the same parasite protein, tryparedoxin peroxidase, were differentially packaged in LEVs, also impacting the interacting molecule of this protein in the host. These data provide new evidence that the interaction with T. cruzi leads to a rapid tissue response through the release of LEVs, reflecting the enrichment of some proteins that could modulate the infection environment.

Bruceine D inhibits the growth of Spodoptera litura by inducing cell apoptosis in the midgut via an oxidative burst.

Spodoptera litura is one of the most harmful lepidoptera pests in China, and is difficult to control due to its strong resistance to the current frequently used insecticide species. The requirement to develop pesticides with novel toxicology mechanisms to control S. litura is urgent. The quassinoid of bruceine D display outstanding systemic properties and strong insecticidal activity against S. litura, which possess notable application potential for integrative management of S. litura, but the mechanism of toxicity remains unclear. In this study, we found that bruceine D exerts potent growth inhibitory activity against S. litura, disrupting the ecdysone and juvenile hormone titers, and causing long-term adverse effects. Association analysis between transcriptomics and metabolomics suggested that bruceine D affected the digestion and absorption capacity of S. litura larvae by inducing a strong oxidative stress response and cell apoptosis in the intestine. Further analysis demonstrated that bruceine D can inhibit the activities of digestive and antioxidant enzymes and induce malondialdehyde (MDA)and reactive oxygen species (ROS) overaccumulation in the midgut. Moreover, the protein level of Bax, cleavage caspase 3, and cytochrome c expressed in cytoplasm (cyto) were up-regulated by bruceine D, while Bcl-2 and cytochrome c expressed in mitochondria (mito) were down-regulated. In addition, there was a noticeable increase in caspase-3 protease activity. Histopathological observations revealed that bruceine D damages the structure of midgut epithelial cells and activates lysosomes, which subsequently disrupts the midgut tissue. Overall, our findings suggested that bruceine D induced excessive ROS accumulation in midgut epithelial cells. The resulting cell apoptosis disrupted midgut tissue, leading ultimately to reduced nutrient digestion and absorption in the midgut and the inhibition of larval growth. © 2024 Society of Chemical Industry.

Predicting individual differences in peak emotional response.

Why does the same experience elicit strong emotional responses in some individuals while leaving others largely indifferent? Is the variance influenced by who people are (personality traits), how they feel (emotional state), where they come from (demographics), or a unique combination of these? In this 2,900+ participants study, we disentangle the factors that underlie individual variations in the universal experience of aesthetic chills, the feeling of cold and shivers down the spine during peak experiences. Here, we unravel the interplay of psychological and sociocultural dynamics influencing self-reported chills reactions. A novel technique harnessing mass data mining of social media platforms curates the first large database of ecologically sourced chills-evoking stimuli. A combination of machine learning techniques (LASSO and SVM) and multilevel modeling analysis elucidates the interacting roles of demographics, traits, and states factors in the experience of aesthetic chills. These findings highlight a tractable set of features predicting the occurrence and intensity of chills-age, sex, pre-exposure arousal, predisposition to Kama Muta (KAMF), and absorption (modified tellegen absorption scale [MODTAS]), with 73.5% accuracy in predicting the occurrence of chills and accounting for 48% of the variance in chills intensity. While traditional methods typically suffer from a lack of control over the stimuli and their effects, this approach allows for the assignment of stimuli tailored to individual biopsychosocial profiles, thereby, increasing experimental control and decreasing unexplained variability. Further, they elucidate how hidden sociocultural factors, psychological traits, and contextual states shape seemingly "subjective" phenomena.

Theoretical Study of Strong Coupling between Molecular Shells and Chiral Plasmons of Gold Nanoparticles Helices.

Chiral plasmonic nanostructures can produce strong chiral optical responses and have potential applications in photonics. Experimentally, metallic nanoparticle helices have been synthesized to achieve strong chiral responses. Strong coupling effects between the quantum emitters and the plasmon have attracted significant attention in the past decade and have been recently extended to the chiral plasmon of nanostructures. However, the strong coupling between molecules and metallic nanosphere helices has not been reported yet. In this article we study theoretically such an effect and examine the modulation of chiral and coupling effects by illumination light and molecular layer thickness. Our study may guide further experimental studies.

Macrocyclic Conformational Switch Coupled with Pyridinium-Induced PET for Fluorescence Detection of Adenosine Triphosphate.

The binding of nucleotides is crucial for signal transduction as it induces conformational protein changes, leading to downstream cellular responses. Synthetic receptors that bind nucleotides and transduce the binding event into global conformational rearrangements are highly challenging to design, especially those that operate in an aqueous solution. Much work is focused on evaluating functionalized dyes to detect nucleotides, whereas coupling of a nucleotide-induced conformational switching to a sensing event has not been reported to date. We disclose synthetic receptors that undergo a global conformational rearrangement upon nucleotide binding. Integrating naphthalimide and the pyridinium ion into the structure enables stabilization of the folded conformation and efficient fluorescence quenching. The binding of a nucleotide rearranges the receptor conformation and alters the strong fluorescence enhancement. The methylpyridinium-containing receptor demonstrated high sensing selectivity for adenosine 5'-triphosphate (ATP) and a record 160-fold fluorescence enhancement. It can detect fluctuations of ATP in HeLa cells and possesses low cytotoxicity. The developed systems present an attractive approach for designing ATP-responsive artificial molecular switches that operate in water and integrate a strong fluorescence response.

Coherent‐Resonance Enhancement of Sensing at the Exceptional Points

AbstractThe branch point singularities in the Riemann surface of the parameter space are known as the exceptional points (EPs), at which two or more eigenvalues and their associated eigenvectors simultaneously coalesce. The abrupt bifurcation property around an EP shows a strong spectral response to external perturbations, and hence, is exploited as a new approach to ultrasensitive sensors. Recently, an intriguing proposal for implementing second‐order EPs in optical resonators with external perturbations has shown the superiority of non‐Hermitian degeneracies in the enhancement of sensing. Of particular importance is further improving the sensitivity to even greater extents. To this end, a novel physical mechanism is proposed, namely introducing extra resonances of external Rayleigh scatterers to accomplish strong‐coupling augmentation in sensing. The results, grounded by both theoretical coupled‐mode‐theory calculations and experimental spectral‐domain measurements, show that the EP‐based sensor working at the coherent resonance equips simultaneously substantial perturbation strength and azimuth sensitivity even subjected to extremely weak perturbations. This work paves the way to a new class of highly functional tunable sensors for applications in optics, microwave and acoustics.

Adaptive properties and ecological plasticity of promising lines of spring soft wheat in the conditions of the Central Non-Black Earth Regions of Russia

In the conditions of the Ryazan region, adaptive properties and ecological plasticity of 8 breeding lines of spring soft wheat (standard Agatha variety) were studied in 2020–2023 according to the "yield" trait using diverse statistical methods. Ecological plasticity (bi), stability (σ2d ), index of environmental conditions (Ij) were determined by S. A. Eberhart, W. A. Russell, variation – by B. A. Dospekhov, stress resistance and genetic flexibility – by A. A. Rossielle, J. Hemblin, index of ecological plasticity – by A. A. Gryaznov, indicator the level of the variety yield stability – according to E. D. Nettevich, homeostaticity (Hom ), breeding value (Sc) – according to V. V. Hangildin, relative stability, stability criterion – according to N. A. Sobolev, multiplicativity (KM) – according to V. A. Dragavtsev. It has been established that the yield level is mostly influenced by the factor "environment" – 51.5 %, the contribution of the factor "genotype" is 11.5 %. The average yield in the experiment was 5.19 t/ha, favorable conditions in 2022 (Ij = 0.50) allowed the yield to be 17.9 % higher than in 2021 (Ij = -0.52). Lines 2-17 (6.24 t/ha) and 21-17 (6.05 t/ha) had high yields, their genetic flexibility index was 5.58 and 5.41 t/ha, respectively. Lines 1-17, 465-17 and 531-17 had the highest resistance to stress (-0.63, -1.00), they are characterized by high yield stability (σ2d = 0.27–0.65) and the least decrease in it under adverse conditions. Strong responsiveness to changes in environmental conditions was noted for lines 290-17, 2-17 and 21-17: bi – 1.25–1.29, KM – 2.22–2.27. According to the degree of homeostaticity, line 1-17 was distinguished (Sc – 4.63, PUSS – 212, Hom – 18.3), these indicators exceeded the average values by 10.2 %, 81.0 abs. %, 98.9 %, respectively. According to the results of the integrated assessment by the ranking method, breeding lines 1-17; 465-17 and 21-17 showed varying degrees of adaptability, environmental stability, homeostaticity and had a high rating. The lowest rating in terms of the sum of the ranks of adaptability and plasticity parameters was obtained by the standard Agate variety.

The Combination of Vascular Endothelial Growth Factor A (VEGF-A) and Fibroblast Growth Factor 1 (FGF1) Modified mRNA Improves Wound Healing in Diabetic Mice: An Ex Vivo and In Vivo Investigation.

Diabetic foot ulcers (DFU) pose a significant health risk in diabetic patients, with insufficient revascularization during wound healing being the primary cause. This study aimed to assess microvessel sprouting and wound healing capabilities using vascular endothelial growth factor (VEGF-A) and a modified fibroblast growth factor (FGF1). An ex vivo aortic ring rodent model and an in vivo wound healing model in diabetic mice were employed to evaluate the microvessel sprouting and wound healing capabilities of VEGF-A and a modified FGF1 both as monotherapies and in combination. The combination of VEGF-A and FGF1 demonstrated increased vascular sprouting in the ex vivo mouse aortic ring model, and topical administration of a combination of VEGF-A and FGF1 mRNAs formulated in lipid nanoparticles (LNPs) in mouse skin wounds promoted faster wound closure and increased neovascularization seven days post-surgical wound creation. RNA-sequencing analysis of skin samples at day three post-wound creation revealed a strong transcriptional response of the wound healing process, with the combined treatment showing significant enrichment of genes linked to skin growth. f-LNPs encapsulating VEGF-A and FGF1 mRNAs present a promising approach to improving the scarring process in DFU.

Comprehensive analysis of a novel subtype of immune microenvironment-derived HPV-infected colorectal cancer

BackgroundThe current study proposed a novel subtype, Human papillomavirus (HPV)-infected colorectal cancer (CRC), to understand the impact of HPV on CRC. MethodsWe assessed the prevalence and clinical implications of HPV in CRC by integrating a single cohort in Guangdong Provincial People's Hospital and public datasets. Differential gene, pathway enrichment, and immune infiltration analysis were conducted to explore the patterns in HPV-infected CRC. Quantitative polymerase chain reaction, cell proliferation, scratch, and flow cytometry assays were employed to validate the impact of HPV on CRC. ResultsThe study revealed a high prevalence of HPV infection in CRC, with infection rates ranging from 10% to 31%. There was also a significant increase in tumor proliferation in HPV-infected CRC. The study showed increased immune cell infiltration, including T cells, γδ T cells, cytotoxic cells, and plasmacytoid dendritic cells in HPV-infected CRC (P < 0.05). Furthermore, our findings confirmed that HPV infection promoted M1 polarization. Our results demonstrated that low ISM2 expression was associated with a less advanced clinical stage (P < 0.001) and better survival outcomes (P = 0.039). Low ISM2 expression correlated with a strong tumor immune response, potentially contributing to the improved survival observed in HPV-infected CRC. ConclusionsThese findings provided a novel subtype of HPV-infected CRC. The subtype with a better prognosis showed a “hot” tumor immune microenvironment that may be responsive to immunotherapy.

Dynamics of Sugars, Organic Acids, Hormones, and Antioxidants in Grape Varieties ‘Italia’ and ‘Bronx Seedless’ during Berry Development and Ripening

Grapes are a globally important fruit with significant economic value, influenced by factors such as sugar content, organic acids, hormones, and antioxidants. Understanding the dynamics of these compounds during grape development and ripening is critical for optimizing berry quality and production. This study investigates the changes in sugar, organic acids, hormones, and antioxidants in two grape varieties, ‘Italia’ and ‘Bronx Seedless’, at various growth stages (BBCH-77, BBCH-79, BBCH-81, BBCH-83, BBCH-85, and BBCH-89). Regarding sugars, significant variations were observed due to grapevine cultivar and phenological stage. ‘Bronx Seedless’ grapes consistently displayed lower sugar content than ‘Italia’ grapes, regardless of the type of sugar being examined. The BBCH-77 stage consistently exhibited lower sugar levels compared to BBCH-89. The varieties ‘Bronx Seedless’ and ‘Italia’ exhibited distinct nutritional profiles, each with their unique advantages in terms of sugar content and organic acid composition. Both varieties were rich in the primary sugar glucose and fructose, with ‘Bronx Seedless’ displaying notably high levels of the beneficial tartaric acid, enhancing its nutritional value. On the other hand, ‘Italia’ stood out for its higher concentrations of fumaric, butyric, and oxalic acids, contributing to its unique taste and health benefits. Throughout their growth stages from BBCH-77 to BBCH-89, an increase in organic acid levels was observed, peaking at the BBCH-85 stage, except for maleic acid. In terms of hormonal content, ‘Italia’ exhibited higher levels compared to ‘Bronx Seedless’. The predominant hormone, abscisic acid (ABA), alongside lower quantities of zeatin, indicated a strong physiological response to environmental and developmental cues in both varieties, with hormone levels increasing as the grapes approached maturity. Antioxidant profiles also varied between the two varieties, with ‘Italia’ consistently showing higher antioxidant levels than ‘Bronx Seedless’. Antioxidant levels consistently increased from BBCH-77 to BBCH-89. This comprehensive analysis contributes to our understanding of the complex processes underlying grape berry development and ripening, with potential implications for enhancing grape quality and refining production strategies.

Water loss after stomatal closure: Quantifying leaf minimum conductance and minimal water use in 9 temperate European tree species during a severe drought.

Residual canopy transpiration (Emin_canop) is a key physiological trait that determines trees' survival time under drought after stomatal closure and after trees have limited access to soil water. Emin_canop mainly depends on leaf minimum conductance (gmin) and vapor pressure deficit (VPD). Here we determined the seasonal variation of gmin and how gmin is related to interspecies variation in leaf cuticular and stomatal traits for nine European tree species in a mature forest. In addition, we determined the species-specific temperature responses of gmin. With this newly obtained insight, we calculated Emin_canop for the nine species for one day at our research site during the 2022 central European hot drought. Our results show that at ambient temperatures gmin ranged from 0.8 to 4.8mmolm-2s-1 across the nine species and was stable in most species throughout the growing season. The interspecies variation of gmin was associated with leaf cuticular and stomatal traits. Additionally, gmin exhibited strong temperature responses and increased, depending on species, by a factor of two to four in the range of 25 to 50°C. For the studied species at the site, during a single hot drought day, Emin_canop standardized by tree size (stem basal area) ranged from 2.0 to 36.7Lm-2, and non-standardized Emin_canop for adult trees ranged from 0.3 to 5.3L. Emin_canop also exhibited species-specific rapid increases under hotter temperatures. Our results suggest that trees, depending on species, need reasonable amounts of water during a drought, even when stomates are fully closed. Species differences in gmin and ultimately Emin_canop can affect, together with other traits, the ability of a tree to keep its tissue hydrated during a drought and is likely to contribute to species-specific differences in drought vulnerability.

The Effects of Information Provision on the Gender Gap in Technology: Experimental Evidence From Course Enrollment and Major Decisions

This article reports on the impacts of a nudge intervention designed to narrow the gender gap in technology education. I randomly assigned approximately 4,000 college freshmen to one of three advising interventions during new student orientation. Students in the treatment group received a brochure containing information about technology courses and were exposed to stereotypical imagery, neutral imagery, or counter-stereotypical imagery. Information provision had a positive impact on both technology course take-up and technology major selection. A stronger response by men led to an overall increase in the gender gap, but this gap is smallest among students exposed to counter-stereotypical imagery.

Green synthesis of silane-assisted fluorescent carbon dots based on sanding dusts and its application in flame-retardant and anti-leaching wood materials

Novel silane-assisted flame-retardant carbon dots (FR-CDs) were synthesized via the hydrothermal carbonization strategy using recycled wood sanding dusts, tris(hydroxymethyl) phosphine oxide (THPO), phosphoric acid (PA), and amino-silane as precursors. The highly transparent FR-CDs suspension appears pale yellow color under daylight and exhibits a strong fluorescence response to light excitations, which helps to keep the original color of the wood and also has broad application prospects for monitoring the leaching behavior of FR-wood. The as-prepared FR-CDs can be applied in FR-wood materials using the facile dipping process owing to their tiny nanoparticles, uniform dispersion, and numerous nitrogen–phosphorus groups. In the flame test, the FR-CDs treated wood composites emitted little smoke initially and maintained primary carbon layer that did not catch fire for over 180 s. The flame-retardancy of the FR-wood materials was confirmed by the thermo-analysis, limiting oxygen index, exposure to a high heat flux (50 kW/cm2), and the propane blowtorch tests (∼600 °C). Moreover, the formation mechanism of the silane-assisted FR-CDs during hydrothermal process and the FR-wood materials with dipping method was proposed. This study provides a facile and efficient strategy for developing highly transparent and cheap flame retardants for the wood materials, which could expand the application of the wood sanding dusts and the silane-assisted carbon-based nanomaterials in the design of anti-leaching flame-retardant materials.

Tuning properties of phase-separated magnetic fluid with temperature

Phase-separated magnetic fluids provide a very strong magnetic response (μ>25) in a liquid state material. Even small fields can cause a notable material response, but this depends on its properties, which are often difficult to control. Here, we investigate how temperature affects the properties of the system, where phase separation is induced by an increase in ionic strength. Following the deformations of individual microscopic droplets, we can extract surface tension, magnetic permeability, and viscosity. We find that the temperature increase does not affect the surface tension, while the magnetic permeability and viscosity increase. Applying this knowledge to induce a shape instability for a drop only using temperature shows the potential of applicability of our findings.

Synchronously manipulating absorption and nonradiative transition of croconaine via donor engineering for efficient NIR-II photothermal theranostics

Organic molecules with strong absorption in the near-infrared (NIR)-II region are highly desired for cancer photothermal theranostics. However, it remains challenges to construct NIR-II photothermal agents with desired optical properties. This study reports a donor engineering approach to simultaneously manipulate the absorption and nonradiative transitions of croconaine dyes. By introducing different donor units with increasing electron donating ability to the backbone, the absorption of the synthesized croconaines were gradually red-shifted to NIR-II region, especially the benzo[c,d]indolium conjugated croconaine (CR1045). The extensive conjugation of CR1045 had a narrower HOMO-LUMO energy gap and strong NIR-II light responsiveness. Importantly, the steric repulsion between this large planar donor and croconate acceptor of CR1045 promotes the formation of a twisted intramolecular charge transfer (TICT) state, making it more prone to direct the absorbed energy towards heat-producing non-radiative decay rather than other dissipative pathways. And the nanoformulated CR1045 exhibits excellent optoacoustic generation capability and ultrahigh photothermal conversion efficiency (∼84%). In vitro and in vivo investigations confirm good optoacoustic imaging and effective photothermal treatment of tumors. Therefore, this work offers insights into donor regulation for the future development of efficient NIR-II photothermal agents.

Immunogenicity and protective efficacy of Ag85A and truncation of PstS1 fusion protein vaccines against tuberculosis

Tuberculosis (TB) is an important public health problem, and the One Health approach is essential for controlling zoonotic tuberculosis. Therefore, a rationally designed and more effective TB vaccine is urgently needed. To enhance vaccine efficacy, it is important to design vaccine candidates that stimulate both cellular and humoral immunity against TB. In this study, we fused the secreted protein Ag85A as the T cell antigen with truncated forms of the mycobacterial cell wall protein PstS1 with B cell epitopes to generate vaccine candidates, Ag85A-tnPstS1 (AP1, AP2, and AP3), and tested their immunogenicity and protective efficacy in mice. The three vaccine candidates induced a significant increase in the levels of T cell-related cytokines such as IFN-γ and IL-17, and AP1 and AP2 can induce more balanced Th1/Th2 responses than AP3. Strong humoral immune responses were also observed in which the production of IgG antibodies including its subclasses IgG1, IgG2c, and IgG3 was tremendously stimulated. AP1 and AP2 induced early antibody responses and more IgG3 isotype antibodies than AP3. Importantly, the mice immunised with the subunit vaccine candidates, particularly AP1 and AP2, had lower bacterial burdens than the control mice. Moreover, the serum from immunised mice can enhance phagocytosis and phagosome-lysosome fusion in macrophages, which can help to eradicate intracellular bacteria. These results indicate that the subunit vaccines Ag85A-tnPstS1 can be promising vaccine candidates for tuberculosis prevention.

Response of the MIMOSIS-1 CMOS Monolithic Active Pixel Sensor to particle beams with different dE/dx

The ultra-thin and highly granular CMOS Monolithic Active Pixel Sensors (MAPS) are typically optimized for high rate high precision tracking, which implies the use of a very thin active medium and digital readout. Both features hamper using the devices for identifying low momentum particles by means of dE/dx. Still, MAPS feature charge sharing and typically clusters of more than one fired pixel per impinging particles are formed. It was previously shown that the number of fired pixels per cluster scales with the dE/dx, which allowed identifying highly ionizing nuclear fragments [1]. Assuming a sufficiently strong response to different dE/dx, this approach could also be considered for distinguishing minimum ionizing particles (MIP) from light fragments like alpha particles in tracking detectors. In this work, we study this response with particle beams with a dE/dx of up to four times the ones of MIPs, for non-irradiated and irradiated chips, with different sensing nodes as implemented in the MIMOSIS-1 prototype used for the vertex detector of the CBM experiment.

Probing delivery of a lipid nanoparticle encapsulated self-amplifying mRNA vaccine using coherent Raman microscopy and multiphoton imaging

The COVID-19 pandemic triggered the resurgence of synthetic RNA vaccine platforms allowing rapid, scalable, low-cost manufacturing, and safe administration of therapeutic vaccines. Self-amplifying mRNA (SAM), which self-replicates upon delivery into the cellular cytoplasm, leads to a strong and sustained immune response. Such mRNAs are encapsulated within lipid nanoparticles (LNPs) that act as a vehicle for delivery to the cell cytoplasm. A better understanding of LNP-mediated SAM uptake and release mechanisms in different types of cells is critical for designing effective vaccines. Here, we investigated the cellular uptake of a SAM-LNP formulation and subsequent intracellular expression of SAM in baby hamster kidney (BHK-21) cells using hyperspectral coherent anti-Stokes Raman scattering (HS-CARS) microscopy and multiphoton-excited fluorescence lifetime imaging microscopy (FLIM). Cell classification pipelines based on HS-CARS and FLIM features were developed to obtain insights on spectral and metabolic changes associated with SAM-LNPs uptake. We observed elevated lipid intensities with the HS-CARS modality in cells treated with LNPs versus PBS-treated cells, and simultaneous fluorescence images revealed SAM expression inside BHK-21 cell nuclei and cytoplasm within 5 h of treatment. In a separate experiment, we observed a strong correlation between the SAM expression and mean fluorescence lifetime of the bound NAD(P)H population. This work demonstrates the ability and significance of multimodal optical imaging techniques to assess the cellular uptake of SAM-LNPs and the subsequent changes occurring in the cellular microenvironment following the vaccine expression.

Neighbour–stranger discrimination in an African wood dove inhabiting equatorial rainforest

We investigated within- and between-individual song variation and song-based neighbour-stranger discrimination in a non-learning bird species, the blue-headed wood-dove (Turtur brehmeri), which inhabits lowland rainforests of West and Central Africa. We found that songs of this species are individually specific and have a high potential for use in individual recognition based on the time–frequency pattern of note distribution within song phrases. To test whether these differences affect behaviour, we conducted playback experiments with 19 territorial males. Each male was tested twice, once with the songs of a familiar neighbour and once with the songs of an unfamiliar stranger. We observed that males responded more aggressively to playback of a stranger’s songs: they quickly approached close to the speaker and spent more time near it. However, no significant differences between treatments were observed in the vocal responses. In addition, we explored whether responses differed based on the song frequency of the focal male and/or that of the simulated intruder (i.e., playback), as this song parameter is inversely related to body size and could potentially affect males’ decisions to respond to other birds. Song frequency parameters (of either the focal male or the simulated intruder) had no effect on the approaching response during playback. However, we found that the pattern of response after playback was significantly affected by the song frequency of the focal male: males with lower-frequency songs stayed closer to the simulated intruder for a longer period of time without singing, while males with higher-frequency songs returned more quickly to their initial song posts and resumed singing. Together, these results depict a consistently strong response to strangers during and after playback that is dependent on a male’s self-assessment rather than assessment of a rival’s strength based on his song frequency. This work provides the first experimental evidence that doves (Columbidae) can use songs for neighbour-stranger discrimination and respond according to a “dear enemy” scheme that keeps the cost of territory defence at a reasonable level.

Effect of low-salt on the survival of mussel Mytilus coruscus and its molecular responses to chronic prolonged low-salt stress

Mussel Mytilus coruscus is a coastal economic culture species. However, massive mortalities associated with low-salt environments caused by persistent rainfall and freshwater inflow threaten its development. Herein, we examined its survival under different low-salt conditions. The survival rate of umbo and eyed larvae significantly decreased with the decline in salinity or prolonged stress time. The umbo larvae were more tolerant to low-salt stress than the eyed larvae. When the salinity levels dropped suddenly, the adults could not survive below 16‰ salinity, and their survival rate decreased faster with the increase in salinity span or the decrease in final stress salinity. However, the adults could tolerate a lower salinity levels when it dropped slowly, and their low-salt tolerance limit was 10‰. Therefore, mussel M. coruscus could adapt to a lower salinity only when the salinity levels dropped gradually. We also explored the physiological and adaptive responses of the foot in response to chronic prolonged low-salt stress by transcriptome analysis. We found that most genes in the “calcium ion binding” term and the osmoregulation-related genes were significantly induced in the salt 12 and 14 groups, suggesting the strong positive response in calcium signal transduction and osmoregulation under prolonged low-salt stress. The HSP70 and IAP genes were upregulated, suggesting that mussel M. coruscus protects itself from low-salt environments by inhibiting apoptosis. The cytoskeleton and cell cycle were inhibited, and the byssus attachment-related genes, such as tyrosinase and foot-protein genes, were suppressed, suggesting a negative response of cell division and byssus thread attachment during prolonged low-salt stress. The enhancement of carbohydrate metabolism indicated its positive role in maintaining energy homeostasis during prolonged low-salt stress. Our findings contribute to the improvement of culture technology and the guidance of selective breeding program for mussel M. coruscus and enhance our understanding of low-salt adaptation mechanism.