Sensitive Species Research Articles

Association Between Reduced Upstream Riparian Forest Cover and Impaired Development of Embryos From Eastern Hellbenders (Cryptobranchus alleganiensis)

ABSTRACT Populations of the Eastern Hellbender, (a large‐bodied, fully aquatic salamander) inhabiting stream reaches with low catchment‐wide riparian forest cover upstream, have experienced population declines and a shift toward a geriatric population age structure. These population declines and demographic shifts might be attributed to reduced embryo viability. Reduced egg quality/viability could negatively affect recruitment and has also been known to trigger filial cannibalism in other species. Therefore, we hypothesized that in comparison to high forest cover sites, hellbender eggs collected from low forest cover sites would have a greater incidence of developmental abnormalities and lower overall viability, and that this would predict whole‐clutch cannibalism by the attending male. We collected a subset of eggs (~20–35) from 99 clutches across sites with variable upstream riparian forest cover and reared these eggs through hatching in stream water under controlled laboratory conditions. At the same time, we monitored the fate of the remaining eggs from the same clutches in the field to document the frequency of whole‐clutch filial cannibalism. We found that eggs collected from sites with lower upstream forest cover had significantly shorter embryonic development times and produced a lower percentage of viable hatchlings (hatchlings with normal development times and morphology). The average modelled viability of hatchlings was 70% higher in sites with the highest forest cover compared to our sites with the lowest forest cover. In contrast to our predictions, we did not find evidence to suggest that egg viability in the lab predicted whole‐clutch cannibalism in the field. Although forest cover was a significant predictor of egg viability and underdevelopment, substantial variance in embryonic developmental traits was unaccounted for in our models suggesting that traits associated with adults (e.g., egg and/or sperm quality) may also play a role in determining developmental outcomes. Further experiments are needed to identify what factors (e.g., egg quality, water quality) disrupt the embryonic development of hellbenders as well as the proximate stimulus that causes adult male hellbenders to eat their young. Our results emphasise the importance of restoring and protecting riparian forest cover to conserve sensitive stream species.

Hardness-Dependent Freshwater Quality Criteria for the Protection of Aquatic Organisms for Cadmium in China

Cadmium poses a significant threat to freshwater aquatic organisms and ecosystems, making it essential to establish regional freshwater quality criteria (FWQC) in China to safeguard these organisms. The toxicity database for cadmium covered 249 acute toxicity data from 52 species (seven phyla and 27 families) and 62 chronic toxicity data from 21 species (four phyla and 12 families). During short-term exposure, Morone saxatilis displayed the most sensitivity to cadmium, whereas Daphnia magna showed the most sensitivity in long-term exposure scenarios. Significant correlations were identified between water hardness and the toxicity data for cadmium, with the acute toxicity coefficient (KATD) at 1.0227 (n = 52, p < 0.05) and the chronic toxicity coefficient (KCTD) at 0.4983 (n = 21, p < 0.05). With the species sensitivity distribution method, the short-term freshwater quality criteria (S-FWQC) were derived with a normal distribution as the best fit (R2 0.9793), while the long-term freshwater quality criteria (L-FWQC) were calculated using a logistic distribution as the best fit (R2 0.9686). The formulas for the S-FWQC and L-FWQC were represented as 10(1.0227×lg(H)−1.5444) and 10(0.4983×lg(H)−1.7549), respectively, with water hardness serving as an independent variable. This study offers valuable insights for improving the management of cadmium to protect freshwater aquatic organisms in China.

The Influence of Light Colour on the Behaviour of Atlantic Cod in an Experimental Setting

Fishing technologies often exploit the visual sensitivity of target species to alter their behaviours. Atlantic cod (Gadus morhua Linnaeus, 1758) are an economically important species, commonly targeted by fisheries in the North Atlantic, yet the behaviour of adult Atlantic cod in reaction to the simultaneous presentation of various light stimuli has not been assessed in an isolated setting to determine if there is a preference for certain light qualities. To assess the influence that artificial light may have on the behaviour of Atlantic cod, we investigated the movement of wild-caught cod in a laboratory setting with green, blue, and white light with a blank control presented in paired choice tests. We predicted that green light would have the greatest influence on cod behaviour and that they would preferentially spend more time in proximity to that light condition. The findings show that cod behaved consistently across trials and across experimental sessions, and that the right side of the arena was preferred regardless of the colours of light presented. These findings indicate that cod do not prefer to spend more time in proximity to certain colours of light in an artificial environment, which has direct implications for animal husbandry, fisheries research, and behavioural ecology.

The implications of climate change for New Zealand’s freshwater fish

Climate change is poised to reshape ecological communities globally by driving species into new environments and altering interactions between species. Conservation efforts should not only address current pressures but also plan for future pressures, such as sensitive species moving into degraded environments or arising problematic trophic interactions. This study sought to assess how climate change may affect the end-of-century distributions of New Zealand’s native and non-native freshwater fish, including consequences for the overlap between trout (a non-native sports fish) and native species vulnerable to trout predation. Random forest modelling was used to predict end-of-century distributions for New Zealand’s freshwater fish based on six hydrologically downscaled global climate models across four representative concentration pathways. Severe climate change impacts could drive nine native fish species to extinction or near-extinction and cause substantial declines in another eight native species. Seven non-natives are also predicted to decline substantially, including a 30-40% reduction in the extent of trout. To avert these potential extinctions, it is crucial to mitigate climate change severity and improve land use impacting freshwater ecosystems.

Acute oral and dermal toxicity parameters of a drug based on D-cyphenothrin, pyriproxyfen and piperonyl butoxide in laboratory animals

The purpose of the research is to study acute oral and dermal toxicity parameters of a drug based on D-cyphenothrin, pyriproxyfen and piperonyl butoxide in laboratory animals.Materials and methods. The study insectoacaricidal drug contains D-cyphenothrin, pyriproxyfen, piperonyl butoxide, hydrogenated castor oil and isopropyl alcohol. The acute toxicity parameters of the drug in 5% solution formulation were studied on 50 white outbred male mice when administered intragastrically, and on 42 outbred male rats when administered orally and on skin. The acute toxicity parameters were calculated using the Litchfield and Wilcoxon method as modified by Z. Rotha, and the drug exposure value on the body was evaluated as per the established classification (GOST 12.1.007). Results and discussion. The following toxicological characteristics were obtained: LD50 of the study drug administered orally to the white mice was 2,656 (2,207.8÷3,187.2) mg/kg, and the white rats, 5,063 (4482÷5818.3) mg/kg. The maximum tolerated dose of the drug was 830 mg/kg for the mice, and 2,075 mg/kg for the rats. Based on the obtained LD50 values, the three-component insectoacaricide can be classified as hazard category 3 (moderately hazardous substances) in experiments on mice, and hazard category 4 (marginally hazardous substances) on rats pursuant to the established hygienic classification. At the same time, different species sensitivity to the drug can be observed in mice and rats. LD50 was more than 30,710 mg/kg in the study of dermal toxicity on the white rats, therefore the drug can be classified as hazard category 4.

A Simple and Cost-Effective Extraction for Piscine Environmental DNA Metabarcoding Using Guanidine Hydrochloride Method.

Environmental DNA (eDNA) metabarcoding is a valuable tool for assessing aquatic biodiversity, but the high cost and complexity of DNA extraction pose challenges for widespread adoption, especially in developing countries. This study presents a cost-effective eDNA extraction method using a guanidine hydrochloride (GuHCl) buffer, proteinase-K digestion, and isopropanol precipitation to improve the detection of fish communities. Comparison with the Qiagen DNeasy Blood & Tissue Kit using MiFish universal primers showed that the GuHCl protocol detected more fish species in freshwater samples, with comparable performance in relative read abundance metrics. However, the GuHCl method exhibited higher PCR inhibition in brackish samples, likely due to salinity and natural inhibitors. The results suggest that the GuHCl-based method is a viable alternative, offering enhanced sensitivity for low-abundance species in freshwater samples and cost savings. This protocol facilitates large-scale eDNA metabarcoding for ecological studies and conservation management efforts.•The GuHCl protocol identified a greater diversity of fish species in freshwater samples than the Qiagen kit, but detected fewer species in brackish water samples.•Both extraction methods demonstrated robust positive correlations in metrics of relative read abundance.

Differential Impact of Wildfire and Rice Straw Ash on the Skin Microbiota of Rana dybowskii Adults and Tadpoles.

Global warming has intensified severe weather conditions and increased the frequency of wildfires, posing significant threats to ecosystems. Moreover, rice straw ash, a byproduct of human agricultural activities, represents an environmental stressor that can further impact these vulnerable ecosystems. These changes particularly impact sensitive species and microorganisms, yet limited research has explored the effects of wildfire ash and agricultural byproducts, such as rice straw ash, on amphibians. This study aims to investigate the effects of both wildfire and rice straw ashes on the skin microbiota of Rana dybowskii tadpoles and adult frogs, using ash aqueous extracts (AEAs). While alpha diversity showed significant variation among tadpoles, it remained stable in adult frogs. Beta diversity analyses revealed distinct microbiota compositions, especially between control and wildfire ash-treated tadpoles. Linear discriminant analysis (LDA) Effect Size (LEfSe) analysis indicated that different ash treatments led to the enrichment of specific microbiota, reflecting the complex effects of environmental changes on amphibian skin microbiota. Specific bacterial enrichments were associated with each treatment group, and phenotypic analysis highlighted bacterial traits, including Aerobic, Anaerobic, Potentially_Pathogenic, and Stress_Tolerant, providing insights into ecological adaptations. Therefore, contrasts wildfire and rice straw ash treatments distinctly influence amphibian skin microbiota and associated bacterial traits. Our findings emphasize the impact of agricultural and wildfire ash on amphibian skin microbiota, offering key ecological insights into the challenges posed by global environmental changes.

Revealing Microplastic Risks in Stratified Water Columns of the East China Sea Offshore

Microplastics have been proven to impact a broad range of marine species significantly. This study investigated the vertical distribution characteristics of microplastics (MPs) to verify their potential toxicity, distribution patterns, and affecting probability on organisms offshore of the East China Sea (ECS), China. Significant variations in MP characteristics across stratified water layers were identified and corroborated through artificial neural network (ANN) analysis. By a combination of species sensitivity distribution (SSD), risk quotient (RQ) and joint pourability curves (JPC) method, this study gave the regional risk thresholds and current risk distributions. Based on SSD, the derived predicted no-effect concentration for the ecosystem was 52.0 items/L (95% confidence interval: 13.7-262.8 items/L), with the 5% species hazardous concentration at 103.6 items/L. The RQ assessment results indicated varying ecological risk levels across different water layers, with the highest risks transitioning from north to south and from surface to bottom layers. Most sites exhibited a moderate risk level, with the highest risks identified in surface water near the Yangtze River Estuary, China. Conversely, the JPC analysis suggested a minimal ecological risk across the study area, emphasizing variable ecological risk contingent on species presence. This study underscores the importance of examining surface and intermediate water layers for marine habitats and organisms, highlighting the necessity of prioritizing investigations into the distribution of MPs across different water layers in the ECS, particularly focusing on buoyant polyester fibers present in the upper water column and the layers beneath the offshore surface.

Empowering Biodiversity Education: Practicing Digital Data Utilization through BioBlitz in a Japanese Curator Course

The digital creation and utilization of biological data, such as occurrence information, are facilitated through the Global Biodiversity Information Facility (GBIF) using Darwin Core standard (Darwin Core Task Group 2009, Raymond M 2021). This standard ensures consistent documentation of species data, enabling efficient sharing across regions. In Japan, publishing biological data in digital formats is becoming essential for biodiversity monitoring. However, there remains a gap between data digitization and its practical use, especially in education. University curatorship programs emphasize data collection but often lack comprehensive training in utilizing these data for research or conservation, limiting students’ opportunities to experience the full scope of data acquisition and application. This report presents a case study of a BioBlitz, conducted in a curatorship program to address this gap（Saito et al. 2020）. A BioBlitz is a collaborative survey where participants aim to identify as many species as possible within a specific area and time frame. Students received lectures on GBIF and the Darwin Core standard, followed by practical training using the iNaturalist (iNaturalist 2024) app. iNaturalist enables real-time species identification and data sharing, making it a valuable educational tool. Thirty-four students were divided into smaller groups of 4–5 to conduct a biological survey in a local park, identifying an average of 90 species in an hour (Fig. 1). After the survey, structured discussions allowed students to evaluate the app’s usability and potential for data utilization. They discussed the strengths and limitations of iNaturalist, including its ease of use, accuracy, and its integration with larger biodiversity datasets. Ethical considerations, such as sharing sensitive species data, were also explored. This hands-on exercise helped students understand the role of digital data in biodiversity conservation. They learned not only about data acquisition but also its real-world applications, including conservation efforts and environmental policymaking. This approach bridges the gap between theoretical knowledge and applied skills. The results indicate that incorporating BioBlitz exercises into educational programs can significantly enhance students' ability to engage with digital biodiversity data, from field collection to analysis and application. Expanding these exercises could better equip future conservation professionals with the skills needed to address global biodiversity challenges. In conclusion, BioBlitz exercises provide an effective model for integrating digital tools into biodiversity education, offering students a comprehensive learning experience. This approach is crucial for preparing the next generation of biodiversity professionals with the technical skills and ethical understanding required for responsible data use in conservation.

Potential Exposure of Aquatic Organisms to Dynamic Visual Cues Originating from Aerial Wind Turbine Blades

For many aquatic species, vision is important for detecting prey, predators, and conspecifics; however, the potential impacts of visual cues from offshore wind turbines have not been investigated in these crucial contexts. There is the possibility of visual cues, originating from moving wind turbine blades, propagating through the air–water interface to impact visually sensitive species. Two classes of visual cues are possible: direct motion cues originating as light reflected from moving turbine blades and indirect cues resulting from an interruption of direct sunlight causing dynamic shadowing when the sun, blade, and receptor are aligned. In both cases, the propagation of cues across the air–water interface is governed by physical principles but modulated in potentially complex ways by the aspects of the local environment that vary with time. Evidence for the extent of the exposure of aquatic organisms to the visual cues arising from moving turbine blades and for the potential response of receptor organisms is sparse. This study considers the physics involved to support the formulation and testing of robust biological hypotheses. Marine migratory salmonid species are considered as an example species because their behaviour in the marine environment is relatively well documented. This study concludes that the aquatic receptor organisms present in the uppermost layer of the sea in the vicinity of wind turbines are potentially exposed to direct motion cues originating from moving turbine blades and also, when the sun elevation angle is greater than ca. 20°, to dynamic shadowing cues.

Network-based investigation of petroleum hydrocarbons-induced ecotoxicological effects and their risk assessment

Petroleum hydrocarbons (PHs) are compounds composed mostly of carbon and hydrogen, originating from crude oil and its derivatives. PHs are primarily released into the environment through the diffusion of oils, resulting from anthropogenic activities like transportation and offshore drilling, and accidental incidents such as oil spills. Once released, these PHs can persist in different ecosystems and cause long-term detrimental ecological impacts. While the hazards associated with such PH contaminations are often assessed by the concentrations of total petroleum hydrocarbons in the environment, studies focusing on the risks associated with individual PHs are limited. In this study, different network-based frameworks were utilized to explore and understand the adverse ecological effects associated with PH exposure. First, a list of 320 PHs was systematically curated from published reports. Next, biological endpoint data from toxicological databases was systematically integrated, and a stressor-centric adverse outcome pathway (AOP) network, linking 75 PHs with 177 ecotoxicologically-relevant high confidence AOPs within AOP-Wiki, was constructed. Further, stressor-species networks, based on reported toxicity concentrations and bioconcentration factors data within ECOTOX, were constructed for 80 PHs and 28 PHs, respectively. It was found that crustaceans are documented to be affected by many of these PHs. Finally, the aquatic toxicity data within ECOTOX was used to construct species sensitivity distributions for PHs, and their corresponding hazard concentrations (HC05), that are harmful to 5% of species in the aquatic ecosystem, were derived. Further, the predicted no-effect concentrations (PNECs) and risk quotients for the US EPA priority polycyclic aromatic hydrocarbons (PAHs) were computed by using their environmental concentration data for Indian coastal and river waters. Overall, this study highlights the importance of using network-based approaches and risk assessment methods to understand the PH-induced toxicities effectively.

Sensitivity of larval Dendropsophus haddadi (Bastos and Pombal 1996), an anuran species from the Brazilian Atlantic Forest, to acute exposure to nitrate.

Nitrogenous pollution has been reported to be a major threat to biodiversity and, therefore, it may be related to the decline of amphibians, the most threatened group of vertebrates in the world. In spite of this, and the widespread release of nitrogenous compounds into the environment, research on the impact of this pollution on Neotropical species remains limited. The aim of this study was to assess the sensitivity of one anuran species inhabiting in the Brazilian Atlantic Forest (Dendropsophus haddadi) to NaNO3 by an acute exposure laboratory experiment, addressing also whether carryover effects exist. Larval mortality increased as time went on in the case of the highly polluted treatments, which also affected swimming performance. Mean lethal concentration (LC50) values revealed that the sensitivity of the study species to NaNO3 was similar to that described for other amphibians, both tropical and temperate species. Additionally, larvae exposed to moderate levels of pollution significantly increased final mass. In spite of this, once larvae were transfered into clean water, no further mortality was recorded, and swimming performance improved. These results indicate that tropical species may not be more vulnerable to chemical pollution than temperate ones, and suggest that they are able to recover from acute short exposure to nitrogenous compounds, all of which represent a new addition to the knowledge of the vulnerability of Dendropsophus haddadi to pollution and, thus, to Neotropical ecotoxicology.

Identification, Pathogenicity, and Fungicide Sensitivity of Colletotrichum Species Associated with Anthracnose on Italian Ryegrass in Southwestern China.

Italian ryegrass (Lolium multiflorum L.) is widely cultivated as an important forage grass worldwide because of its high nutritional value and good palatability. Anthracnose caused by Colletotrichum species was a common and new emerging disease of Italian ryegrass. In this study, 88 Colletotrichum isolates were collected from diseased leaves of Italian ryegrass planting regions in Sichuan, Chongqing, and Guizhou provinces of southwestern China between 2019 and 2022. By the pure culture technique, 15 representative single-spore isolates were obtained for further study. Multilocus phylogenetic analysis coupled with morphological features showed that these isolates were finally identified as six new record species: C. cereale of the C. graminicola species complex, C. fioriniae and C. nymphaeae of the C. acutatum species complex, C. boninense and C. citricola of the C. boninense species complex, and C. nageiae. Pathogenicity tests indicated that all species could induce anthracnose symptoms; of these, C. cereale was more invasive than other species, followed by C. fioriniae, C. nageiae, C. citricola, and C. boninense; C. nymphaeae was the weakest pathogenic species to Italian ryegrass plants (P ≤ 0.05). Fungicide sensitivity assays showed that iprodione, propineb, and oxime·tebuconazole had strong inhibitory effects on the mycelial growth of six Colletotrichum species; in addition, azoxystrobin and fludioxonil also significantly inhibited the mycelial growth of C. nymphaeae and C. fioriniae, respectively. These results provide the basis for the diagnosis and detection in the field, pathogen identification, and management of anthracnose on Italian ryegrass.

Sensitivity of Southcentral U.S. Johnsongrass Accessions to Selected Herbicides

Abstract New technologies in grain sorghum allow for the use of multiple acetyl CoA carboxylase- (ACCase) or acetolactate synthase- (ALS) inhibiting herbicides for johnsongrass control. With the growing issue of herbicide resistance, producers need to understand which herbicides will successfully control johnsongrass accessions. To determine the efficacy of herbicides recently registered or ones with potential to become available for use in grain sorghum, johnsongrass seeds were collected from 2017 to 2021 in Arkansas, Kansas, Texas, and Oklahoma and were screened for sensitivity to fluazifop, quizalofop, nicosulfuron, and imazamox. Additionally, glyphosate sensitivity was evaluated because of its use before planting or postharvest. Quizalofop resulted in 100% mortality of all johnsongrass accessions. Of the johnsongrass accessions evaluated, 89% were completely controlled with glyphosate. The ALS inhibitors nicosulfuron and imazamox resulted in 100% mortality of all Oklahoma accessions, but failures occurred on samples from other states. One accession from Kansas, 12 from Texas, and eight from Arkansas were found to have reduced sensitivity to nicosulfuron and imazamox. If producers plan to plant grain sorghum in areas with johnsongrass populations, an ACCase-inhibitor herbicide will most likely provide effective control. Imazamox and nicosulfuron, in conjunction with the appropriate trait, can be utilized in areas with sensitive johnsongrass populations or where other sensitive grass species are present.

Bridging Knowledge and Data Gaps in Odonata Rarity: A South Korean Case Study Using Multispecies Occupancy Models and the Rabinowitz Framework.

Accurate assessment of species rarity and conservation status requires an approach that integrates data-driven models with established ecological knowledge. In this study, we applied multispecies occupancy (MSO) and latent factor multispecies occupancy (LFMSO) models to estimate the occurrence of 133 Odonata species in South Korea. Using the model outputs, we implemented the Rabinowitz rarity framework to conduct data-based rarity assessments, which were then compared with known ecological information, including geographic ranges, habitat preferences, regional Red List statuses, and citizen science observations. Our findings reveal both alignments and discrepancies between these data-driven rarity assessments and traditional ecological knowledge. For example, species classified as near threatened (NT) or vulnerable (VU) on the regional Red List generally corresponded with high-rarity classifications based on the Rabinowitz framework. However, significant inconsistencies were identified, particularly for certain lentic Odonata species traditionally considered common. These results suggest that spatial biases in field surveys, combined with limited access to data on legally protected species, can impede accurate rarity assessments. These findings underscore the need for standardized survey protocols and improved data-sharing policies for sensitive species to reduce biases and enhance the reliability of rarity assessments. This is essential for effective conservation planning and biodiversity management in freshwater ecosystems.

Analysis of Key Environmental Variables Affecting Fish Communities and Species Distribution in Asian Lotic Ecosystems

In 2011, Korea installed artificial structures on four rivers to secure water resources and reduce flood damage; however, these structures have altered ecosystems and aquatic communities. This study analyzed fish communities and environmental variables at 72 sites in the Geumgang River. Fish communities and environmental variables before weir installation were examined using site data from 2008 to 2009. The results showed that Cyprinidae dominated the 70 observed species. A self-organizing map categorized the 72 sites into four groups based on fish communities. Sensitive and insectivorous species decreased, whereas tolerant and omnivorous species increased from Groups I to IV. Twenty-one indicator species were identified, with fewer and less distinct distribution patterns in Groups II and III than in Groups I and IV. The fish assessment index (FAI) showed a decline in grades A and B and an increase in grades C and D from Groups I to IV. Correlation analysis between the FAI and environmental variables indicated that fish communities in the Geumgang River were mainly influenced by water quality, reflecting altitude gradients and pollution levels. This study’s findings are anticipated to significantly inform water management strategies for the Geumgang, Yeongsangang, Nakdonggang, and Hangang Rivers.

Physiological changes in shrub species due to different sources of dust pollution in an urban environment.

Plants effectively filter ambient air by adsorbing particulate matter. The correct selection of landscape plants can exert greater dust retention benefits in different polluted areas. However, few studies have focused on the dust retention ability and related physiological responses of plants under continuous dust pollution from different dust sources. Here, we assessed the particle retention dynamics and plant physiology (chlorophyll content, soluble protein content, soluble sugar content, and peroxidase activity) of six shrubs (Berberis thunbergii var. atropurpurea, Ligustrum vicaryi, Rosa multiflora, Sorbaria sorbifolia, Swida alba, and Syzyga oblata) under continuous dust pollution from different dust sources (industrial sources: area below the direction of the coal-fired thermal power plant in Chengyang District, Qingdao, China; traffic sources: both sides of the road in each direction at the intersection of Great Wall Road and Zhengyang Road, Chengyang District, Qingdao, China; clean sources: Qingdao Agricultural University Campus, Qingdao Olympic Sculpture Park). The results showed that R. multiflora had the highest dust retention per unit leaf area of 3.27 ± 0.018g·m-2 and 2.886 ± 0.02g·m-2 in the experimental treatments of fuel source dust and clean source dust, respectively. The chlorophyll content of the tested shrubs significantly decreased due to the influence of dust treatment time, the range of cellular osmoregulatory substances (soluble sugars, soluble proteins, proline) tended to first increase and then decrease, and the antioxidant enzyme activities (superoxide dismutase, peroxidase) tended to increase and then decrease after continuous dust treatment. The greatest physiological changes were observed in plants within the industrial dust treatment area. The peroxidase activity and chlorophyll could be used as sensitive indicators of dust pollution in plants. R. multiflora showed better resistance to dust and had a greater dust retention capacity than other shrubs, making it more suitable for planting as a greening tree in industrial and traffic-polluted areas. S. alba and S. sorbifolia are sensitive to dust pollution, so they can be used as sensitive tree species to indicate atmospheric dust pollution. Our results may help design a feasible approach for urban shrub greening.

Investigation on chemical composition and insecticidal activity against Anopheles gambiae of essential oil obtained by co-distillation of Cymbopogon citratus and Hyptis suaveolens from Western Burkina Faso

BackgroundEssential oils of Cymbopogon citratus and Hyptis suaveolens are known for their insecticidal properties, but remain ineffective against mosquitoes resistant to synthetic insecticides. In order to improve insecticidal properties of these plants, this study aimed to investigate the chemical composition and insecticidal activity against Anopheles gambiae mosquitoes of essential oil obtained by co-distillation of dry leaves of C. citratus and H. suaveolens.MethodsEssential oils were extracted by hydrodistillation from dry leaves of C. citratus and H. suaveolens, separately, then from the mixture of the dry leaves of the two plants in mass ratio 50/50. Each pure essential oil and the mixture obtained either by co-distillation or by combining pure essential oils in volume ratio 50/50 were then analysed by GC/MS. All essential oils and Deltamethrin 0.05% (positive control) were tested on two species of mosquitoes of the genus Anopheles gambiae according to the World Health Organization standard methods.ResultsEssential oil obtained by co-distillation mainly contained piperitone (40.80%), 1,8-cineole (24.64%), p-menth-4(8)-ene (13.20%), limonene (6.09%) and α-pinene (4.73%). However, the mixture of pure essential oils of these two plants mostly contained geranial (20.74%), neral (16.42%), 1,8-cineole (19.79%), sabinene (6.03%) and β-pinene (3.87%). The essential oil of C. citratus mainly contained geranial (41.49%), neral (32.83%), β-myrcene (13.66%) and geraniol (3.49%) while the major constituents of essential oil of H. suaveolens were 1,8-cineole (39.58%), sabinene (12.06%), β-pinene (7.73%), α-terpinolene (6.72%) and (E)-caryophyllene (7.49%). At the dose of 1%, all essential oils, except that of H. suaveolens, induced about 100% of mortality on the sensitive species of An. gambiae. However, on the resistant species at the same dose, the essential oil obtained by co-distillation induced the highest mortality (53.44%). The essential oils of C. citratus, H. suaveolens and the mixture of the two pure essential oils caused respectively 2.47, 15.28 and 18.33% of mortality. The synthetic insecticide caused 100 and 14.84% of mortality respectively on the sensitive and resistant species of An. gambiae.ConclusionEssential oil obtained by co-distillation showed good insecticidal efficacy against a resistant species of An. gambiae and might constitute a new solution to fight against mosquitoes resistant to synthetic insecticides.

Chemical composition and biological activities of essential oils from Cymbopogon schoenanthus (L.) Spreng.: a Saharan plant from Ghardaïa region (Algeria)

The essential oils (EOs) of Cymbopogon schoenanthus (L.) Spreng. collected from Ghardaïa Province were analyzed for their chemical composition by GC-MS analysis. The results showed fifty-one identified compounds representing 94.34% of the whole EOs, with β-eudesmol (11.35%) and α-elemol (10.84%) as major compounds. The TAC, DPPH, and FRAP antioxidant activities of the EOs were moderate, while an important inhibition of 63.54 ± 2.41% was obtained for the β-carotene bleaching assay. The results of the antibacterial activity show that gentamicin had an inhibition zone of 21.66 ± 0.57 mm while Bacillus cereus was the most sensitive species (inhibition zone of 20.75 ± 0.50 mm). The wound-healing activity results showed contraction percentages on the 20th day of 99.35 ± 0.12%, which was similar to the positive control 1% allantoin (98.33 ± 0.17%). Our results show that C. schoenanthus is a source of many bioactive compounds with well-known antioxidant, antibacterial and wound-healing properties.

Inhibitory effects of N-trans-cinnamoyltyramine on growth of invasive weeds and weedy rice.

N-trans-cinnamoyltyramine (NTCT) has been identified from an allelopathic Vietnamese rice accession OM 5930. This study employed bioassays to analyze NTCT's effects on shoot and root growth of multiple test and weed species. NTCT demonstrated potent inhibitory effects on cress, lettuce, canola, palmer amaranth, timothy, barnyardgrass, red sprangletop, and weedy rice, with increasing concentrations leading to substantial reductions in growth in all species. Linear regression analysis of dose response curves revealed ED50 values for NTCT, providing critical insights into the concentration required for 50% growth inhibition in each species. They revealed high sensitivity of the test species cress and lettuce, intermediate sensitivities of barnyardgrass, red sprangletop, timothy, and amaranth, and comparatively lower sensitivity of two weedy rice accessions. The findings underscore NTCT's efficacy in suppressing the growth of a wide range of weeds, including both grasses and broadleaf species. As such, NTCT may hold promise as a tool for sustainable weed management, particularly in addressing herbicide-resistant weeds in diverse ecological settings.