Global arthropod beta-diversity is spatially and temporally structured by latitude.

Global biodiversity gradients are generally expected to reflect greater species replacement closer to the equator. However, empirical validation of global biodiversity gradients largely relies on vertebrates, plants, and other less diverse taxa. Here we assess the temporal and spatial dynamics of global arthropod biodiversity dynamics using a beta-diversity framework. Sampling includes 129 sampling sites whereby malaise traps are deployed to monitor temporal changes in arthropod communities. Overall, we encountered more than 150,000 unique barcode index numbers (BINs) (i.e. species proxies). We assess between site differences in community diversity using beta-diversity and the partitioned components of species replacement and richness difference. Global total beta-diversity (dissimilarity) increases with decreasing latitude, greater spatial distance and greater temporal distance. Species replacement and richness difference patterns vary across biogeographic regions. Our findings support long-standing, general expectations of global biodiversity patterns. However, we also show that the underlying processes driving patterns may be regionally linked.

Meaningful inclusion of people living with HIV as a model for workplace policies: Key findings from the project PEER study.

BACKGROUND: As a large number of people live with HIV, it is worthwhile to examine the integration of this group in the workplace. OBJECTIVE: To investigate how the operationalization of GIPA/MEPA supports workplace policies and practices for PLHIV. The study aims to explore what is being offered to support PLHIV in community-based agencies and what can be done to enhance the offerings. METHODS: For this community-based research, 2 bilingual online surveys were sent to 150 Canadian organizations that work closely with PLHIV or offer support to them. One of the surveys was for Executive Directors of these organizations while the other was sent to peers; i.e. PLHIV whose job is to offer services to PLHIV. Questions in the surveys varied between open-ended, binary, and Likert. RESULTS: GIPA/MEPA are implemented in most organizations and Executive Directors affirmed that PLHIV and their impacts on the workplace are valued. There is a consensus among Executive Directors that formal support is provided but most respondents argued that this support is not specific for PLHIV. More than half of respondents were either unaware or uncertain about the existence of informal support. Peer-employees claimed that one of the challenges of disclosing HIV to receive peer support is that they may face stigma. CONCLUSION: The application of GIPA/MEPA results in positive outcomes in the workplace. The study emphasizes the need to facilitate access to informal support.

Assessing the effects of a drought experiment on the reproductive phenology and ecophysiology of a wet tropical rainforest community.

Climate change is expected to increase the intensity and occurrence of drought in tropical regions, potentially affecting the phenology and physiology of tree species. Phenological activity may respond to a drying and warming environment by advancing reproductive timing and/or diminishing the production of flowers and fruits. These changes have the potential to disrupt important ecological processes, with potentially wide-ranging effects on tropical forest function. Here, we analysed the monthly flowering and fruiting phenology of a tree community (337 individuals from 30 species) over 7 years in a lowland tropical rainforest in northeastern Australia and its response to a throughfall exclusion drought experiment (TFE) that was carried out from 2016 to 2018 (3 years), excluding approximately 30% of rainfall. We further examined the ecophysiological effects of the TFE on the elemental (C:N) and stable isotope (δ13C and δ15N) composition of leaves, and on the stable isotope composition (δ13C and δ18O) of stem wood of four tree species. At the community level, there was no detectable effect of the TFE on flowering activity overall, but there was a significant effect recorded on fruiting and varying responses from the selected species. The reproductive phenology and physiology of the four species examined in detail were largely resistant to impacts of the TFE treatment. One canopy species in the TFE significantly increased in fruiting and flowering activity, whereas one understory species decreased significantly in both. There was a significant interaction between the TFE treatment and season on leaf C:N for two species. Stable isotope responses were also variable among species, indicating species-specific responses to the TFE. Thus, we did not observe consistent patterns in physiological and phenological changes in the tree community within the 3 years of TFE treatment examined in this study.

Vapour pressure deficit modulates hydraulic function and structure of tropical rainforests under nonlimiting soil water supply.

Atmospheric conditions are expected to become warmer and drier in the future, but little is known about how evaporative demand influences forest structure and function independently from soil moisture availability, and how fast-response variables (such as canopy water potential and stomatal conductance) may mediate longer-term changes in forest structure and function in response to climate change. We used two tropical rainforest sites with different temperatures and vapour pressure deficits (VPD), but nonlimiting soil water supply, to assess the impact of evaporative demand on ecophysiological function and forest structure. Common species between sites allowed us to test the extent to which species composition, relative abundance and intraspecific variability contributed to site-level differences. The highest VPD site had lower midday canopy water potentials, canopy conductance (gc ), annual transpiration, forest stature, and biomass, while the transpiration rate was less sensitive to changes in VPD; it also had different height-diameter allometry (accounting for 51% of the difference in biomass between sites) and higher plot-level wood density. Our findings suggest that increases in VPD, even in the absence of soil water limitation, influence fast-response variables, such as canopy water potentials and gc , potentially leading to longer-term changes in forest stature resulting in reductions in biomass.

Solution structure of the N-terminal extension domain of a Schistosoma japonicum asparaginyl-tRNA synthetase.

Several secreted proteins from helminths (parasitic worms) have been shown to have immunomodulatory activities. Asparaginyl-tRNA synthetases are abundantly secreted in the filarial nematode Brugia malayi (BmAsnRS) and the parasitic flatworm Schistosoma japonicum (SjAsnRS), indicating a possible immune function. The suggestion is supported by BmAsnRS alleviating disease symptoms in a T-cell transfer mouse model of colitis. This immunomodulatory function is potentially related to an N-terminal extension domain present in eukaryotic AsnRS proteins but few structure/function studies have been done on this domain. Here we have determined the three-dimensional solution structure of the N-terminal extension domain of SjAsnRS. A protein containing the 114 N-terminal amino acids of SjAsnRS was recombinantly expressed with isotopic labelling to allow structure determination using 3D NMR spectroscopy, and analysis of dynamics using NMR relaxation experiments. Structural comparisons of the N-terminal extension domain of SjAsnRS with filarial and human homologues highlight a high degree of variability in the ß-hairpin region of these eukaryotic N-AsnRS proteins, but similarities in the disorder of the C-terminal regions. Limitations in PrDOS-based intrinsically disordered region (IDR) model predictions were also evident in this comparison. Empirical structural data such as that presented in our study for N-SjAsnRS will enhance the prediction of sequence-homology based structure modelling and prediction of IDRs in the future.Communicated by Ramaswamy H. Sarma.

Antioxidant and Anti-Inflammatory Activities of Endemic Plants of the Australian Wet Tropics.

Plants have been a vital source of natural antioxidants since ancient times. Plants growing under various abiotic stress conditions often produce more defensive secondary metabolites such as phenolics, flavonoids, and terpenoids during adaptation to the environment. Many of these secondary metabolites are known to possess antioxidant and anti-inflammatory properties. This study tested seven plants sourced from the mountaintop areas (above 1000 m elevation) of Mount Lewis National Park (falls under the Wet Tropics of Queensland), Australia, for their antioxidant and anti-inflammatory activities. Of the seven studied plants, hydroethanolic extracts of six plants (Leptospermum wooroonooran, Ceratopetalum hylandii, Linospadix apetiolatus, Garcinia brassii, Litsea granitica, and Polyscias willmottii) showed high 2,2-diphenyl-1-picrylhydrazyl (DPPH)-free radical scavenging activity in a dose-dependent (25-1000 µg/mL) manner. At the highest concentration of 1 mg/mL, the DPPH free radical scavenged percentage varied between 75.4% and 92.3%. Only the species Alyxia orophila was inactive in the DPPH free radical scavenging assay. Pseudo-IC50 values of the extracts' ferric reducing antioxidant power (FRAP) based on dose-response curves showed a significant positive correlation with total phenolic content. Five out of the seven plants, namely G. brassii, C. hylandii, L. apetiolatus, L. wooroonooran, and A. orophila, showed inhibitory effects on the secretion of proinflammatory cytokines, tumour necrosis factor (TNF), and interleukins (IL)-23 in a lipopolysaccharide (LPS)-stimulated human peripheral blood mononuclear cells (PBMCs) assay. The results of this study demonstrate the value of tropical mountaintop plants in the biodiscovery of antioxidant and anti-inflammatory lead compounds.

Bridge to the future: Important lessons from 20 years of ecosystem observations made by the OzFlux network.

In 2020, the Australian and New Zealand flux research and monitoring network, OzFlux, celebrated its 20th anniversary by reflecting on the lessons learned through two decades of ecosystem studies on global change biology. OzFlux is a network not only for ecosystem researchers, but also for those 'next users' of the knowledge, information and data that such networks provide. Here, we focus on eight lessons across topics of climate change and variability, disturbance and resilience, drought and heat stress and synergies with remote sensing and modelling. In distilling the key lessons learned, we also identify where further research is needed to fill knowledge gaps and improve the utility and relevance of the outputs from OzFlux. Extreme climate variability across Australia and New Zealand (droughts and flooding rains) provides a natural laboratory for a global understanding of ecosystems in this time of accelerating climate change. As evidence of worsening global fire risk emerges, the natural ability of these ecosystems to recover from disturbances, such as fire and cyclones, provides lessons on adaptation and resilience to disturbance. Drought and heatwaves are common occurrences across large parts of the region and can tip an ecosystem's carbon budget from a net CO2 sink to a net CO2 source. Despite such responses to stress, ecosystems at OzFlux sites show their resilience to climate variability by rapidly pivoting back to a strong carbon sink upon the return of favourable conditions. Located in under-represented areas, OzFlux data have the potential for reducing uncertainties in global remote sensing products, and these data provide several opportunities to develop new theories and improve our ecosystem models. The accumulated impacts of these lessons over the last 20 years highlights the value of long-term flux observations for natural and managed systems. A future vision for OzFlux includes ongoing and newly developed synergies with ecophysiologists, ecologists, geologists, remote sensors and modellers.

Forest system hydraulic conductance: partitioning tree and soil components.

Soil-leaf hydraulic conductance determines canopy-atmosphere coupling in vegetation models, but it is typically derived from ex-situ measurements of stem segments and soil samples. Using a novel approach, we derive robust in-situ estimates for whole-tree conductance (ktree ), 'functional' soil conductance (ksoil ), and 'system' conductance (ksystem , water table to canopy), at two climatically different tropical rainforest sites. Hydraulic 'functional rooting depth', determined for each tree using profiles of soil water potential (Ψsoil ) and sap flux data, enabled a robust determination of ktree and ksoil . ktree was compared across species, size classes, seasons, height above nearest drainage (HAND), two field sites, and to alternative representations of ktree ; ksoil was analysed with respect to variations in site, season and HAND. ktree was lower and changed seasonally at the site with higher vapour pressure deficit (VPD) and rainfall; ktree differed little across species but scaled with tree circumference; rsoil (1/ksoil ) ranged from 0 in the wet season to 10× less than rtree (1/ktree ) in the dry season. VPD and not rainfall may influence plot-level k; leaf water potentials and sap flux can be used to determine ktree , ksoil and ksystem ; Ψsoil profiles can provide mechanistic insights into ecosystem-level water fluxes.

The three major axes of terrestrial ecosystem function.

The leaf economics spectrum1,2 and the global spectrum of plant forms and functions3 revealed fundamental axes of variation in plant traits, which represent different ecological strategies that are shaped by the evolutionary development of plant species2. Ecosystem functions depend on environmental conditions and the traits of species that comprise the ecological communities4. However, the axes of variation of ecosystem functions are largely unknown, which limits our understanding of how ecosystems respond as a whole to anthropogenic drivers, climate and environmental variability4,5. Here we derive a set of ecosystem functions6 from a dataset of surface gas exchange measurements across major terrestrial biomes. We find that most of the variability within ecosystem functions (71.8%) is captured by three key axes. The first axis reflects maximum ecosystem productivity and is mostly explained by vegetation structure. The second axis reflects ecosystem water-use strategies and is jointly explained by variation in vegetation height and climate. The third axis, which represents ecosystem carbon-use efficiency, features a gradient related to aridity, and is explained primarily by variation in vegetation structure. We show that two state-of-the-art land surface models reproduce the first and most important axis of ecosystem functions. However, the models tend to simulate more strongly correlated functions than those observed, which limits their ability to accurately predict the full range of responses to environmental changes in carbon, water and energy cycling in terrestrial ecosystems7,8.

Stability of tropical forest tree carbon-water relations in a rainfall exclusion treatment through shifts in effective water uptake depth.

Increasing severity and frequency of drought is predicted for large portions of the terrestrial biosphere, with major impacts already documented in wet tropical forests. Using a 4-year rainfall exclusion experiment in the Daintree Rainforest in northeast Australia, we examined canopy tree responses to reduced precipitation and soil water availability by quantifying seasonal changes in plant hydraulic and carbon traits for 11 tree species between control and drought treatments. Even with reduced soil volumetric water content in the upper 1 m of soil in the drought treatment, we found no significant difference between treatments for predawn and midday leaf water potential, photosynthesis, stomatal conductance, foliar stable carbon isotope composition, leaf mass per area, turgor loss point, xylem vessel anatomy, or leaf and stem nonstructural carbohydrates. While empirical measurements of aboveground traits revealed homeostatic maintenance of plant water status and traits in response to reduced soil moisture, modeled belowground dynamics revealed that trees in the drought treatment shifted the depth from which water was acquired to deeper soil layers. These findings reveal that belowground acclimation of tree water uptake depth may buffer tropical rainforests from more severe droughts that may arise in future with climate change.

Thermal optima of gross primary productivity are closely aligned with mean air temperatures across Australian wooded ecosystems.

Gross primary productivity (GPP) of wooded ecosystems (forests and savannas) is central to the global carbon cycle, comprising 67%-75% of total global terrestrial GPP. Climate change may alter this flux by increasing the frequency of temperatures beyond the thermal optimum of GPP (Topt ). We examined the relationship between GPP and air temperature (Ta) in 17 wooded ecosystems dominated by a single plant functional type (broadleaf evergreen trees) occurring over a broad climatic gradient encompassing five ecoregions across Australia ranging from tropical in the north to Mediterranean and temperate in the south. We applied a novel boundary-line analysis to eddy covariance flux observations to (a) derive ecosystem GPP-Ta relationships and Topt (including seasonal analyses for five tropical savannas); (b) quantitatively and qualitatively assess GPP-Ta relationships within and among ecoregions; (c) examine the relationship between Topt and mean daytime air temperature (MDTa) across all ecosystems; and (d) examine how down-welling short-wave radiation (Fsd) and vapour pressure deficit (VPD) influence the GPP-Ta relationship. GPP-Ta relationships were convex parabolas with narrow curves in tropical forests, tropical savannas (wet season), and temperate forests, and wider curves in temperate woodlands, Mediterranean woodlands, and tropical savannas (dry season). Ecosystem Topt ranged from 15℃ (temperate forest) to 32℃ (tropical savanna-wet and dry seasons). The shape of GPP-Ta curves was largely determined by daytime Ta range, MDTa, and maximum GPP with the upslope influenced by Fsd and the downslope influenced by VPD. Across all ecosystems, there was a strong positive linear relationship between Topt and MDTa (Adjusted R2 : 0.81; Slope: 1.08) with Topt exceeding MDTa by >1℃ at all but two sites. We conclude that ecosystem GPP has adjusted to local MDTa within Australian broadleaf evergreen forests and that GPP is buffered against small Ta increases in the majority of these ecosystems.

Acclimation of leaf respiration temperature responses across thermally contrasting biomes.

Short-term temperature response curves of leaf dark respiration (R-T) provide insights into a critical process that influences plant net carbon exchange. This includes how respiratory traits acclimate to sustained changes in the environment. Our study analysed 860 high-resolution R-T (10-70°C range) curves for: (a) 62 evergreen species measured in two contrasting seasons across several field sites/biomes; and (b) 21 species (subset of those sampled in the field) grown in glasshouses at 20°C : 15°C, 25°C : 20°C and 30°C : 25°C, day : night. In the field, across all sites/seasons, variations in R25 (measured at 25°C) and the leaf T where R reached its maximum (Tmax ) were explained by growth T (mean air-T of 30-d before measurement), solar irradiance and vapour pressure deficit, with growth T having the strongest influence. R25 decreased and Tmax increased with rising growth T across all sites and seasons with the single exception of winter at the cool-temperate rainforest site where irradiance was low. The glasshouse study confirmed that R25 and Tmax thermally acclimated. Collectively, the results suggest: (1) thermal acclimation of leaf R is common in most biomes; and (2) the high T threshold of respiration dynamically adjusts upward when plants are challenged with warmer and hotter climates.

Does the Addition of Zinc Oxide Nanoparticles Improve the Antibacterial Properties of Direct Dental Composite Resins? A Systematic Review.

A promising approach to improve the poor antibacterial properties of dental composite resins has been the addition of metal oxide nanoparticles into the resin matrix. This systematic review aimed to determine whether the addition of zinc oxide nanoparticles (ZnO-NPs) improves the antibacterial properties of direct dental composite resins. This review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and registered with the PROSPERO database: CRD42019131383. A systematic literature search was conducted using the following databases: Medline (Ovid), the Cochrane Library, SCOPUS, CINAHL, Web of Science, Trove, Google Scholar, World Cat, and OpenGrey. The initial search retrieved 3178 results, which were then screened against inclusion and exclusion criteria, resulting in a total of four studies that were eligible for qualitative synthesis within this review. All the included studies were in vitro non-randomized post-test design experimental studies. A lack of congruity in the results obtained from these studies that used different tests to evaluate antibacterial activity was evident. Although some studies demonstrated a significant improvement of antibacterial properties in composites containing at least 1% ZnO-NPs (wt %), they are unlikely to present any clear clinical advantage due to the short lifetime of observed antibacterial properties.

Australian Scorpion Hormurus waigiensis Venom Fractions Show Broad Bioactivity Through Modulation of Bio-Impedance and Cytosolic Calcium.

Scorpion venoms are a rich source of bioactive molecules, but characterisation of toxin peptides affecting cytosolic Ca2+, central to cell signalling and cell death, is limited. We undertook a functional screening of the venom of the Australian scorpion Hormurus waigiensis to determine the breadth of Ca2+ mobilisation. A human embryonic kidney (HEK293) cell line stably expressing the genetically encoded Ca2+ reporter GCaMP5G and the rabbit type 1 ryanodine receptor (RyR1) was developed as a biosensor. Size-exclusion Fast Protein Liquid Chromatography separated the venom into 53 fractions, constituting 12 chromatographic peaks. Liquid chromatography mass spectroscopy identified 182 distinct molecules with 3 to 63 components per peak. The molecular weights varied from 258 Da-13.6 kDa, with 53% under 1 kDa. The majority of the venom chromatographic peaks (tested as six venom pools) were found to reversibly modulate cell monolayer bioimpedance, detected using the xCELLigence platform (ACEA Biosciences). Confocal Ca2+ imaging showed 9/14 peak samples, with molecules spanning the molecular size range, increased cytosolic Ca2+ mobilization. H. waigiensis venom Ca2+ activity was correlated with changes in bio-impedance, reflecting multi-modal toxin actions on cell physiology across the venom proteome.

Environmental impacts of abrasive blasting of transmission towers in protected areas.

In Australia, and other parts of the world, tower infrastructure in electricity transmission networks are nearing the end of their asset life. In changing economic, political and regulatory environments Transmission Network Service Providers are implementing new approaches to asset management and reinvestment, such as refurbishment to extend the life of existing assets, instead of replacement. As part of these refurbishment efforts, abrasive blasting and recoating is being employed to remove corrosion and extend the life of steel electricity transmission towers. New controls and procedures have been developed to manage the most likely impacts associated with the abrasive blasting of transmission towers. However, little or no data have been available on the environmental impacts of abrasive blasting or the effectiveness of management procedures currently being used to mitigate potential adverse environmental impacts.We conducted an integrated study on the impacts of abrasive blasting, which brought together on-site research; modelling; and controlled laboratory trials. The study was undertaken during a transmission tower refurbishment project within the World Heritage listed Wet Tropics Region in Queensland, Australia. Measured metal deposition around towers due to blasting, was primarily as large particles (>PM10) at 12-30 m from the tower. Soil concentrations of metals were highest under towers, with a small number of samples showing elevated zinc at 12-30 m. The presence of spent abrasive media and dust on the geofabric material used under the towers and up to 15 m from the tower base, as part of control measures used to contain the abrasive products, indicates that deposition also occurs between 0 and 12 m from the tower.The potential impacts of the abrasive blasting technique on plants and invertebrates appear to be low. Five species of tropical rainforest tree seedlings exposed to abrasive blasting dust at worst-case levels had no negative impact on physiological performance or plant health. This research will assist Transmission Network Service Providers and other operators of corroded linear infrastructure to plan and implement mitigating management actions and procedures during abrasive blasting projects and assist regulators and the community to better understand the impacts of the practice.

Multi-drug cocktails: Impurities in commonly used illicit drugs seized by police in Queensland, Australia.

BACKGROUND: Impurities in commonly used illicit drugs raise concerns for unwitting consumers when pharmacologically active adulterants, especially new psychoactive substances (NPS), are used. This study examines impurities detected in illicit drugs seized in one Australian jurisdiction. METHODS: Queensland Health Forensic and Scientific Services provided analytical data. Data described the chemical composition of 9346 samples of 11 illicit drugs seized by police during 2015-2016. Impurities present in primary drugs were summarized and tabulated. A systematic search for published evidence reporting similar analyses was conducted. RESULTS: Methamphetamine was the primary drug in 6608 samples, followed by MDMA (1232 samples) and cocaine (516 samples). Purity of primary drugs ranged from ∼30% for cocaine, 2-CB and GHB to >90% for THC, methamphetamine, heroin and MDMA. Methamphetamine and MDMA contained the largest variety of impurities: 22 and 18 variants, respectively. Drug adulteration patterns were broadly similar to those found elsewhere, including NPS, but in some primary drugs impurities were found which had not been reported elsewhere. Psychostimulants were adulterated with each other. Levamisole was a common impurity in cocaine. Psychedelics were adulterated with methamphetamine and NPS. Opioids were quite pure, but some samples contained methamphetamine and synthetic opioids. CONCLUSIONS: Impurities detected were mostly pharmacologically active adulterants probably added to enhance desired effects or for active bulking. Given the designer nature of these drug cocktails, the effects of the adulterated drugs on users from possible complex multi-drug interactions is unpredictable. Awareness-raising among users, research into complex multi-drug effects and ongoing monitoring is required.

The validity of optimal leaf traits modelled on environmental conditions.

The ratio of leaf intercellular to ambient CO2 (χ) is modulated by stomatal conductance (gs ). These quantities link carbon (C) assimilation with transpiration, and along with photosynthetic capacities (Vcmax and Jmax ) are required to model terrestrial C uptake. We use optimization criteria based on the growth environment to generate predicted values of photosynthetic and water-use efficiency traits and test these against a unique dataset. Leaf gas-exchange parameters and carbon isotope discrimination were analysed in relation to local climate across a continental network of study sites. Sun-exposed leaves of 50 species at seven sites were measured in contrasting seasons. Values of χ predicted from growth temperature and vapour pressure deficit were closely correlated to ratios derived from C isotope (δ13 C) measurements. Correlations were stronger in the growing season. Predicted values of photosynthetic traits, including carboxylation capacity (Vcmax ), derived from δ13 C, growth temperature and solar radiation, showed meaningful agreement with inferred values derived from gas-exchange measurements. Between-site differences in water-use efficiency were, however, only weakly linked to the plant's growth environment and did not show seasonal variation. These results support the general hypothesis that many key parameters required by Earth system models are adaptive and predictable from plants' growth environments.

The Aromatic Head Group of Spider Toxin Polyamines Influences Toxicity to Cancer Cells.

Spider venoms constitute incredibly diverse libraries of compounds, many of which are involved in prey capture and defence. Polyamines are often prevalent in the venom and target ionotropic glutamate receptors. Here we show that a novel spider polyamine, PA366, containing a hydroxyphenyl-based structure is present in the venom of several species of tarantula, and has selective toxicity against MCF-7 breast cancer cells. By contrast, a polyamine from an Australian funnel-web spider venom, which contains an identical polyamine tail to PA366 but an indole-based head-group, is only cytotoxic at high concentrations. Our results suggest that the ring structure plays a role in the cytotoxicity and that modification to the polyamine head group might lead to more potent and selective compounds with potential as novel cancer treatments.

Changes in predator exposure, but not in diet, induce phenotypic plasticity in scorpion venom.

Animals embedded between trophic levels must simultaneously balance pressures to deter predators and acquire resources. Venomous animals may use venom toxins to mediate both pressures, and thus changes in this balance may alter the composition of venoms. Basic theory suggests that greater exposure to a predator should induce a larger proportion of defensive venom components relative to offensive venom components, while increases in arms races with prey will elicit the reverse. Alternatively, reducing the need for venom expenditure for food acquisition, for example because of an increase in scavenging, may reduce the production of offensive venom components. Here, we investigated changes in scorpion venom composition using a mesocosm experiment where we manipulated scorpions' exposure to a surrogate vertebrate predator and live and dead prey. After six weeks, scorpions exposed to surrogate predators exhibited significantly different venom chemistry compared with naive scorpions. This change included a relative increase in some compounds toxic to vertebrate cells and a relative decrease in some compounds effective against their invertebrate prey. Our findings provide, to our knowledge, the first evidence for adaptive plasticity in venom composition. These changes in venom composition may increase the stability of food webs involving venomous animals.

Scorpion toxin peptide action at the ion channel subunit level.

This review categorizes functionally validated actions of defined scorpion toxin (SCTX) neuropeptides across ion channel subclasses, highlighting key trends in this rapidly evolving field. Scorpion envenomation is a common event in many tropical and subtropical countries, with neuropharmacological actions, particularly autonomic nervous system modulation, causing significant mortality. The primary active agents within scorpion venoms are a diverse group of small neuropeptides that elicit specific potent actions across a wide range of ion channel classes. The identification and functional characterisation of these SCTX peptides has tremendous potential for development of novel pharmaceuticals that advance knowledge of ion channels and establish lead compounds for treatment of excitable tissue disorders. This review delineates the unique specificities of 320 individual SCTX peptides that collectively act on 41 ion channel subclasses. Thus the SCTX research field has significant translational implications for pathophysiology spanning neurotransmission, neurohumoral signalling, sensori-motor systems and excitation-contraction coupling. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'