Effects of overwintering on the transcriptome and fitness traits in a damselfly with variable voltinism across two latitudes.

Winter diapause consists of cessation of development that allows individuals to survive unfavourable conditions. Winter diapause may bear various costs and questions have been raised about the evolutionary mechanisms maintaining facultative diapause. Here, we explored to what extent a facultative winter diapause affects life-history traits and the transcriptome in the damselfly Ischnura elegans, and whether these effects were latitude-specific. We collected adult females at central and high latitudes and raised their larvae in growth chambers. Larvae were split into a non-diapausing and post-winter (diapausing) cohort, were phenotyped and collected for a gene expression analysis. At the phenotypic level, we found no difference in survival between the two cohorts, and the post-winter cohort was larger and heavier than the non-winter cohort. These effects were mostly independent of the latitude of origin. At the transcriptomic level, wintering affected gene expression with a small fraction of genes significantly overlapping across latitudes, especially those related to morphogenesis. In conclusion, we found clear effects of diapause on the phenotype but little evidence for latitudinal-specific effects of diapause. Our results showed a shared transcriptomic basis underpinning diapause demonstrated, here, at the intraspecific level and supported the idea of evolutionary convergence of the response to diapause across organisms.

On the wings of dragons: Wing morphometric differences in the sexually dichromatic common whitetail skimmer dragonfly, Plathemis lydia (Odonata: Libellulidae).

Sexual dimorphism is common throughout the animal kingdom, leading to sex-specific phenotypic differences. The common whitetail skimmer dragonfly, Plathemis lydia (Drury, 1773), is sexually dichromatic, where males of this species display a conspicuous white abdomen and females display a dark brown abdomen. Differences in abdomen conspicuousness between male and female P. lydia are likely attributed to differences in selective pressure where males use their white conspicuous abdomen during male-male territorial chases. We hypothesized that male P. lydia would exhibit wing morphology adaptations to better offset the costs of predation and territoriality and that these adaptations would differ from females. We used field-collected images to quantify differences in body length, wing length, wing area, wing shape, and wing loading between male and female P. lydia. Our results show that male P. lydia have significantly shorter fore and hind wings relative to body size with a higher wing loading when compared to females. We also found that male P. lydia have narrower and pointier fore and hind wings compared to females. These results are consistent with the idea that males are adapted for faster flight, specifically higher acceleration capacity, and higher agility whereas females are adapted for higher maneuverability.

Research of biomimetic corrugation on the blade flutter suppression in large-scale wind turbine systems.

Aiming at the blade flutter of large horizontal-axis wind turbines, a method by utilizing biomimetic corrugation to suppress blade flutter is first proposed. By extracting the dragonfly wing corrugation, the biomimetic corrugation airfoil is constructed, finding that mapping corrugation to the airfoil pressure side has better aerodynamic performance. The influence of corrugation type, amplitudeλ, and intensity on airfoil flutter is analyzed using orthogonal experiment, which determines that theλhas the greatest influence on airfoil flutter. Based on the fluctuation range of the moment coefficient ΔCm, the optimal airfoil flutter suppression effect is obtained when the type is III,λ= 0.6, and intensity is denser (n= 13). The effective corrugation layout area in the chord direction is determined to be the leading edge, and the ΔCmof corrugation airfoil is reduced by 7.405%, compared to the original airfoil. The application of this corrugation to NREL 15 MW wind turbine 3D blades is studied, and the influence of corrugation layout length in the blade span direction on the suppressive effect is analyzed by fluid-structure interaction. It is found that when the layout length is 0.85 R, the safety marginSfreaches a maximum value of 0.3431 Hz, which is increased 2.940%. The results show that the biomimetic corrugated structure proposed in this paper can not only improve the aerodynamic performance by changing the local flow field on the surface of the blade, but also increase the structural stiffness of the blade itself, and achieve the effect of flutter suppression.

Total environment sentinels: Dragonflies as ambivalent/amphibiotic bioindicators of damage to soil and freshwater.

Discerning the impact of anthropogenic impacts requires the implementation of bioindicators that quantify the susceptibilities and vulnerabilities of natural terrestrial and aquatic ecosystems to perturbation and transformation. Although legal regulations in Brazil recognize the value of bioindicators in monitoring water quality, the depreciation of soil conditions has yet to receive adequate attention. Thus, our study aimed to evaluate the potential of odonates (dragonflies and damselflies) as amphibiotic bioindicators to reflect the correlation between the degradation of aquatic and terrestrial habitats in pasture-dominated landscapes. We assessed the relationship between the biotic indices of Odonata and the conservation status of preserved riparian landscapes adjacent to anthropogenically altered pastures in 40 streams in the Brazilian savannah. Our results support the hypothesis that Odonata species composition may be a surrogate indicator for soil and water integrity, making them promising sentinels for detecting environmental degradation and guiding conservation strategies in human-altered landscapes. Importantly, while the Zygoptera/Anisoptera species ratio is a useful bioindicator tool in Brazilian forest, it is less effective in the open savannah here, and so an alternative index is required. Importantly, while the Zygoptera/Anisoptera species ratio is a useful bioindicator tool in Brazilian forest, it is less effective in the open savannah here, and so an alternative index is required. On the other hand, our results showed the Dragonfly Biotic Index to be a suitable tool for assessing freshwater habitats in Brazilian savannah. We also identified certain bioindicator species at both ends of the environment intactness spectrum.

Sum or mean in calculation of qualitative scoring methods using the Dragonfly Biotic Index, and an alternative approach facilitating conservation prioritization.

Qualitative scoring methods are tools for rapid freshwater health assessments. Total score is often calculated as the sum or mean of the values of the species involved, with minor nuances in interpretation, but with significant implications. We used the Dragonfly Biotic Index (DBI) calculated on Central European odonate species to demonstrate these implications. Each species within a community has a score ranging from 0 (widespread generalists) to 9 (sensitive specialists). A total score is calculated as the sum of the scores of all species (DBIsum) or is calculated by dividing by species richness (DBImean). Despite this duality, there has been little debate on either approach. Using simulated scenarios (high vs low richness, presence or absence of high- or low-scoring species), we tested the implications of DBIsum and DBImean and suggested a total score calculation for conservation prioritization based on permutation. This algorithm shows the percentile of a community compared to a set of randomly assembled communities of the same species richness. We also present the 'dragDBI' package for the statistical software R, a tool for more automated DBI-based environmental health assessments. Our permutational calculation is applicable to other macroinvertebrate-based scoring methods, such as the Biological Monitoring Working Party and the Average Score Per Taxon.

Variations in the Odonata Assemblages: How Do the Dry Season and Water Bodies Influence Them?

Diverse abiotic and biotic factors drive the ecological variation of communities across spatial and temporal dimensions. Within the Amazonian landscape, various freshwater environments exhibit distinct physicochemical characteristics. Thus, our study delved into the fluctuations of Odonata assemblages amidst distinct water bodies within Amazonia, encompassing two distinct climatic seasons. Comparative analysis was conducted on Odonata species diversity and assemblage composition across a blackwater pond, a lake, and a stream, spanning the initiation and culmination of the dry season in the southwestern Amazon region in Peru. Our methodology involved capturing adult Odonata using entomological nets on three separate occasions between 11:00 and 14:00 h for each water body in May (beginning of the dry season) and October (end of the dry season) of 2018. We also evaluated the influence of temperature, precipitation, and percent cloud cover on the abundance and richness of adult Odonata. Species richness and composition differed among the three water bodies in both periods of the dry season. No effect of the dry season periods on species richness and abundance was observed. However, except in the oxbow lake, the more abundant species were substituted to the end of the dry season. Our study highlights the influence of water body types on Odonata species diversity and composition. The effects of the sampling period during the dry season may not be immediately apparent in conventional diversity metrics, such as species richness and abundance. Instead, its effects manifest predominantly in the relative abundance of the species that compose these assemblages.

Sub-lethal effects of the insecticide, imidacloprid, on the responses of damselfly larvae to chemosensory cues indicating predation risk.

Insecticides, including the widely used neonicotinoids, can affect both pest and non-target species. In addition to lethal effects, these insecticides at sub-lethal levels may cause disruption to sensory perception and processing leading to behavioural impairments. In this laboratory experiment, we investigated the effects of a 10-day exposure to the neonicotinoid insecticide, imidacloprid, on the behaviour of larvae of the damselfly, Lestes congener. In tests of baseline activity, imidacloprid concentrations of 1.0 and 10.0 µg/L caused significant reductions in foraging behaviour. Moreover, in response to chemical cues that indicate a potential risk to the larvae, imidacloprid caused the loss of an appropriate antipredator response (reduced foraging) depending on the concentration and duration of exposure. Imidacloprid at 0.1 µg/L caused the loss of responses toward the odour of a beetle (Dytiscus spp.) predator after 10 days of exposure, whereas 1.0 µg/L caused lost responses toward both the predator odour and injured conspecific cues (i.e., alarm cues) and after only 2 days of exposure. However, at 10.0 µg/L, larvae responded appropriately to both cues throughout the duration of the study, suggesting compensatory responses to imidacloprid at higher concentrations. Hence, the lack of appropriate responses at 1.0 µg/L likely resulted from a cognitive impairment rather than chemical alteration of these important chemosensory cues. In the natural environment, such effects will likely cause decreased survivorship in predator encounters. Hence, imidacloprid exposure, even at low concentrations, could have adverse consequences for chemosensory ecology of this damselfly species.

Genetic diversity and phylogeographic patterns of the peacock jewel-damselfly, Rhinocypha fenestrella (Rambur, 1842).

Despite is known to have widespread distribution and the most active species of the family Chlorocyphidae, the molecular data of Rhinocypha fenestrella (Rambur, 1842) are relatively scarce. The present study is the first that examined the genetic diversity and phylogeographic pattern of the peacock jewel-damselfly R. fenestrella by sequencing the cytochrome C oxidase I (cox1) and 16S rRNA gene regions from 147 individuals representing eight populations in Malaysia. A total of 26 and 10 unique haplotypes were revealed by the cox1 and 16S rRNA genes, respectively, and 32 haplotypes were recovered by the concatenated sequences of cox1+16S. Analyses indicated that haplotype AB2 was the most frequent and the most widespread haplotype in Malaysia while haplotype AB1 was suggested as the common ancestor haplotype of the R. fenestrella that may arose from the Negeri Sembilan as discovered from cox1+16S haplotype network analysis. Overall haplotype and nucleotide diversities of the concatenated sequences were Hd = 0.8937 and Pi = 0.0028, respectively, with great genetic differentiation (FST = 0.6387) and low gene flow (Nm = 0.14). Population from Pahang presented the highest genetic diversity (Hd = 0.8889, Pi = 0.0022, Nh = 9), whereas Kedah population demonstrated the lowest diversity (Hd = 0.2842, Pi = 0.0003, Nh = 4). The concatenated sequences of cox1+16S showed genetic divergence ranging from 0.09% to 0.97%, whereas the genetic divergence for cox1 and 16S rRNA genes were 0.16% to 1.63% and 0.01% to 0.75% respectively. This study provides for the first-time insights on the intraspecific genetic diversity, phylogeographic pattern and ancestral haplotype of Rhinocypha fenestrella. The understanding of molecular data especially phylogeographic pattern can enhance the knowledge about insect origin, their diversity, and capability to disperse in particular environments.

Desirable Strong and Tough Adhesive Inspired by Dragonfly Wings and Plant Cell Walls.

The production of wood-based panels has a significant demand for mechanically strong and flexible biomass adhesives, serving as alternatives to nonrenewable and toxic formaldehyde-based adhesives. Nonetheless, plywood usually exhibits brittle fracture due to the inherent trade-off between rigidity and toughness, and it is susceptible to damage and deformation defects in production applications. Herein, inspired by the microstructure of dragonfly wings and the cross-linking structure of plant cell walls, a soybean meal (SM) adhesive with great strength and toughness was developed. The strategy was combined with a multiple assembly system based on the tannic acid (TA) stripping/modification of molybdenum disulfide (MoS2@TA) hybrids, phenylboronic acid/quaternary ammonium doubly functionalized chitosan (QCP), and SM. Motivated by the microstructure of dragonfly wings, MoS2@TA was tightly bonded with the SM framework through Schiff base and strong hydrogen bonding to dissipate stress energy through crack deflection, bridging, and immobilization. QCP imitated borate chemistry in plant cell walls to optimize interfacial interactions within the adhesive by borate ester bonds, boron-nitrogen coordination bonds, and electrostatic interactions and dissipate energy through sacrificial bonding. The shear strength and fracture toughness of the SM/QCP/MoS2@TA adhesive were 1.58 MPa and 0.87 J, respectively, which were 409.7% and 866.7% higher than those of the pure SM adhesive. In addition, MoS2@TA and QCP gave the adhesive good mildew resistance, durability, weatherability, and fire resistance. This bioinspired design strategy offers a viable and sustainable approach for creating multifunctional strong and tough biobased materials.

Mosquitocidal Susceptibility and Non-Target Effects of Tricholoma equestre Mushroom (Agaricomycetes) on the Immature Stages of Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus.

The worldwide scientific community is well aware that mosquitoes are the sole agents responsible for transmitting various dreadful diseases and critical illnesses caused by vector-borne pathogens. The primary objective of this current research was to evaluate the effectiveness of methanol extract from Tricholoma equestre mushroom in controlling the early life stages of Culex quinquefasciatus Say, Anopheles stephensi Liston, and Aedes aegypti (Linnaeus in Hasselquist) mosquitoes. The larvae, pupae and eggs of these mosquitoes were exposed to four different concentrations (62.5 to 500 ppm). After 120 h of treatment, the methanol extract of T. equestre exhibited ovicidal activity ranging from 66% to 80% against the eggs of the treated mosquitoes. It also demonstrated promising larvicidal and pupicidal activity with LC50 values of 216-300 and 230-309 ppm against the early life stages of all three mosquito species. Extensive toxicity studies revealed that the methanol extract from T. equestre had no harmful effects on non-target organisms. The suitability index (SI) or predator safety factor (PSF) indicated that the methanol extract did not harm Poecilia reticulata Peters 1859, (predatory fish), Gambusia affinis S. F. Baird & Girard 1853, dragonfly nymph and Diplonychus indicus Venkatesan & Rao 1871 (water-bug). Gas chromatography-mass spectrometry (GCMS) analysis identified key compounds, including 3-butenenitrile, 2-methyl-(25.319%); 1-butanol, 2-nitro-(18.87%) and oxalic acid, heptyl propyl ester (21.82%) which may be responsible for the observed activity. Furthermore, the formulation based on the methanol extract demonstrated similar effectiveness against all treated mosquitoes at the laboratory level and was found to be non-toxic to mosquito predators. This groundbreaking research represents the first confirmation that methanol extract from T. equestre could be effectively employed in preventing mosquito-borne diseases through mosquito population control programs.

QSPR for the prediction of critical micelle concentration of different classes of surfactants using machine learning algorithms.

The determination of the critical micelle concentration (CMC) is a crucial factor when evaluating surfactants, making it an essential tool in studying the properties of surfactants in various industrial fields. In this present research, we assembled a comprehensive set of 593 different classes of surfactants including, anionic, cationic, nonionic, zwitterionic, and Gemini surfactants to establish a link between their molecular structure and the negative logarithmic value of critical micelle concentration (pCMC) utilizing quantitative structure-property relationship (QSPR) methodologies. Statistical analysis revealed that a set of 14 significant Mordred descriptors (SlogP, GATS6d, nAcid, GATS8dv, GATS4dv, PEOE_VSA11, GATS8d, ATS0p, GATS1d, MATS5p, GATS3d, NdssC, GATS6dv and EState_VSA4), along with temperature, served as appropriate inputs. Different machine learning methods, such as multiple linear regression (MLR), random forest regression (RFR), artificial neural network (ANN), and support vector regression (SVM), were employed in this study to build QSPR models. According to the statistical coefficients of QSPR models, SVR with Dragonfly hyperparameter optimization (SVR-DA) was the most accurate in predicting pCMC values, achieving (R2 = 0.9740, Q2 = 0.9739, r‾m2 = 0.9627, and Δrm2 = 0.0244) for the entire dataset.

Description of the final stadium larva of Anisopleura furcata Selys, 1891 (Odonata: Euphaeidae) from Thailand.

The final stadium larva of Anisopleura furcata Selys, 1891 is described and illustrated. The larva can be separated from all known Anisopleura Selys, 1853 larvae by the following characters: the profusion of elongated tubercles on the labrum and antefrons, the presence of a long bifid spur on the outer margin of the mandibles, presence of a row of claviform setae on dorsal apex of tarsus, and antennae 8-segmented. The inner lobe of the labial palps forms a tiny truncate tooth broadly similar to the condition in all other known members of the genus. Diagnostic features that separate this species from potentially syntopic euphaeid genera are discussed.

Stolleagrion foghnielseni (Odonata, Cephalozygoptera, Dysagrionidae) gen. et sp. nov.: a new odonatan from the PETM recovery phase of the earliest Ypresian Fur Formation, Denmark.

We describe the new genus and species Stolleagrion foghnielseni n. gen. et sp. from the Fur Formation in northwestern Denmark based on a single fossil wing. This is the first odonatan described from the earliest part of the PETM recovery phase of the early Eocene. A combination of nine wing character states are considered to be diagnostic of the Dysagrionidae Cockrell only together with the cephalozygopteran head; however, the combination of these nine plus the presence of Ax0 is also diagnostic without the head. By this, we assign Stolleagrion foghnielseni to the Dysagrionidae and reassess the position of other odonates previously treated as cf. Dysagrionidae.

A revision of Lestidae Calvert, 1901 (Odonata: Zygoptera) from Colombia, with the first record of Lestes dichrostigma Calvert, 1909.

The cosmopolitan family Lestidae Calvert, 1901 has two widely distributed genera in the Americas: Archilestes Selys, 1862, and Lestes Leach, 1815. In Colombia, this family is represented by 11 species. In this study, we present a diagnosis of Lestidae species in Colombia based on a thorough review of the countrys main entomological collections. A total of 258 specimens representing ten species were examined. The species L. dichrostigma Calvert, 1909, is recorded for the first time. The presence of L. henshawi Calvert, 1907 is excluded, and the taxonomic status of L. sternalis (Navs, 1930) is discussed. Finally, we present distribution maps, photographs of Lestidae species, taxonomical important structures, and taxonomic keys for both males and females.

The Dragonflies and Damselflies (Insecta: Odonata) of Canada: species list, geographical distribution, status, and conservation ranks.

As of August 2023, 220 species in 57 genera and 10 families of damselflies and dragonflies (Insecta: Odonata) are recorded for Canada. Since the publication of the first edition in 2005, 14 species have been added to the list; one,Neurocordulia obsoleta (Say) has been removed because of a misidentification and another, Sympetrum occidentale, has been to synonymy. Conservation ranks are given for species in all 13 provinces and territories. English and French names for all listed species are included. Literature sources are discussed and presented, as is information on species status and the addition and exclusion of species. Sections on taxonomy and variation, subspecies, presumed hybrids, the introduction of exotic species, notable range extensions and observations, and conservation and protection are also provided.

Description of the female of Leptagrion jeromei Lencioni, Vilela & Furieri, 2021 (Odonata: Coenagrionidae) with taxonomic notes on the male.

The female of Leptagrion jeromei Lencioni, Vilela & Furieri, 2021 is described, illustrated, and diagnosed based on a specimen collected in epiphytic bromeliads at the Federal University of Sergipe ( (B0545), BRAZIL, Federal University of Sergipe, So Cristvo, -10.92707, -37.10100, 30 m asl, 6.x.2023, A.B.S. Farias & J.C. Santos leg.). Additionally, we provide information on its biology, ecology, and taxonomic notes, along with illustrations of the collected males.

Taxonomic revisions of some Neotropical Zygoptera (Odonata).

We provide updated synonymies for various genera and species of Neotropical Zygoptera based on examination of specimens and literature accompanied by justifications and supported by illustrations. The following generic synonyms are proposed: Austrotepuibasis Machado & Lencioni, 2011 and Pseudotepuibasis Stand-Prez & Prez-Gutirrez, 2020 are junior synonyms of Tepuibasis De Marmels, 2007; Fredyagrion Lencioni, 2022, Kiautagrion Lencioni, 2022, Nathaliagrion Lencioni, 2022, and Machadagrion Lencioni, 2022 are junior synonyms of Leptagrion Selys, 1876; Juenagrion Lencioni, 2023 is a junior synonym of Telebasis Selys, 1865. The following specific synonyms are proposed: Lestes fernandoi Costa, Souza & Muzn, 2006 is a junior synonym of Lestes debellardi De Marmels, 1992; Lestes tikalus Kormondy, 1959 is a junior synonym of Lestes scalaris Gundlach, 1888; Palaemnema brasiliensis Machado, 2009 is a junior synonym of Palaemnema brevignoni Machet, 1990; Hetaerina aurora Ris, 1918 is a junior synonym of Hetaerina duplex Selys, 1853; Hetaerina hebe Selys, 1853 is a junior synonym of Hetaerina longipes Hagen in Selys, 1853; Mnesarete mariana Machado, 1996 is a junior synonym of Mnesarete guttifera (Selys, 1873); Acanthagrion hartei Muzn & Lozano, 2005 is a junior synonym of Acanthagrion obsoletum (Frster, 1914); Oxyagrion bruchi Navs, 1924 is a junior synonym of Oxyagrion ablutum (Calvert, 1909); Austrotepuibasis alvarengai Machado & Lencioni, 2011 and Austrotepuibasis manolisi Machado & Lencioni, 2011 are junior synonyms of Tepuibasis demarmelsi (Machado & Lencioni, 2011). Helveciagrion Machado, 1980 is again considered a junior synonym of Telebasis Selys, 1865; Leptagrion auriceps St. Quentin, 1960 is again considered a junior synonym of Leptagrion macrurum (Burmeister, 1839), and Homeoura sobrina (Schmidt, 1943) is transferred back to Ischnura Charpentier. The following synonymies are tentatively proposed pending further examination of specimens: Philogenia lankesteri Calvert, 1924 is a possible junior synonym of Philogenia carrillica Calvert, 1907; Leptagrion jeromei Lencioni, Vilela & Furieri in Vilela, Garcia Jnior, Furieri & Lencioni, 2021 is a possible junior synonym of Leptagrion andromache Hagen in Selys, 1876; Phoenicagrion flavescens Machado, 2010 is a possible junior synonym of Phoenicagrion flammeum (Selys, 1876); Tuberculobasis mammilaris (Calvert, 1909) is a possible junior synonym of Tuberculobasis croceum (Burmeister, 1839) new combination. The status of Agrion rufovittatum Blanchard, 1846 is briefly discussed.

Last instar larva of the critically endangered Oxyagrion franciscoi Machado & Bede, 2016 (Odonata: Coenagrionidae) from Serra da Canastra National Park.

Oxyagrion franciscoi Machado & Bede, 2016 is a critically endangered damselfly species endemic to the Serra da Canastra National Park, Brazil, a vital environmental reserve within the Cerrado hotspot for biodiversity conservation. Here we reared, illustrated, and described the last instar larva of O. franciscoi.

A remarkable new synthemistid from New Caledonia (Odonata: Anisoptera: Synthemistidae s. str.). Taxonomic and phylogenetic note on New Caledonian Synthemistidae and erection of a new genus.

The new species, Calesynthemis jeanlegrandi sp. nov., dedicated to the late Jean Legrand, is described and illustrated based on a single pair of specimens from Mont Pani, New Caledonia. The male of this large species has unusual strongly sinuous and distally down curved white cerci 7 mm long and exhibits on abdominal segment 10 a remarkable clump of strong setae mimicking a dorsal horn. The female wingspan slightly exceeds 100 mm. In addition, on the basis of adult and larval characters, Neocaledosynthemis gen. nov. is erected to accommodate two other New Caledonian synthemistids, Synthemis fenella Campion (type species) and Synthemis ariadne Lieftinck. New Caledonian synthemistids are probably more closely related to Parasynthemis Carle than to Synthemis Selys Longchamps, both from Australia.

Significant biomagnification of methylmercury in songbird nestlings through a rice-based food web: Insights from stable mercury isotopes.

To elucidate the sources and transfer of mercury (Hg) in terrestrial food chains, particularly in heavily Hg-contaminated rice paddy ecosystems, we collected rice leaves, invertebrates, and Russet Sparrow nestlings from a clear food chain and analyzed the dietary compositions and potential Hg sources using stable Hg isotopes coupled with a Bayesian isotope mixing model (BIMM). Our findings indicated that MeHg exposure is dominant through the dietary route, with caterpillars, grasshoppers, and katydids being the main prey items, while the less provisioned spiders, dragonflies, and mantises contributed the most of the Hg to nestlings. We found minimal MIF but certain MDF in this terrestrial food chain and identified two distinct MeHg sources of dietary exposure and maternal transfer. We firstly found that the dietary route contributed substantially (almost tenfold) more MeHg to the nestlings than maternal transfer. These findings offer new insights into the integration of Hg from the dietary route and maternal transfers, enhancing our understanding of fluctuating Hg exposure risk during the nestling stage. Our study suggested that Hg isotopes combined with BIMM is an effective approach for tracing Hg sources in birds and for gaining in-depth insight into the trophic transfers and biomagnification of MeHg in food chains.