The increasing threat of anthropogenic pollution to marine ecosystems underscores the need for robust risk assessment through ecotoxicology. While standard bioassays rely on model organisms chosen for their sensitivity and ease of laboratory use, there is growing interest in ecologically relevant species such as jellyfish, to reflect marine environmental complexity. Among jellyfish, hydrozoans represent valuable models in neuroscience and developmental and evolutionary biology; however, they are still unrepresented in ecotoxicology. Here, we propose the hydrozoan Clytia hemisphaerica as a novel model for acute toxicity testing. Following the optimization of test conditions, juvenile medusae were exposed to an anionic surfactant, Sodium Dodecyl Sulfate (SDS), assessing mortality and sub-lethal endpoints, including behaviour and feeding, after 24 and 48 h. SDS exposure triggered a concentration-dependent increase in mortality, with LC50 values of 16.3 mg/L at 24 h and 9.2 mg/L at 48 h. Feeding rate emerged as the most sensitive sub-lethal indicator (EC50(48 h) = 5.2 mg/L). Notably, jellyfish transferred to clean seawater after exposure showed partial recovery of motility and feeding ability, highlighting potential resilience to short-term chemical stress. This study is the first to report SDS toxicity in a hydrozoan and provides a proof-of-concept demonstration of the feasibility of using C. hemisphaerica in marine ecotoxicological assays. Our results emphasize the value of including behavioural endpoints, such as swimming and feeding, to achieve a more comprehensive assessment of pollutant impacts on jellyfish.
Nickel ferrite nanoparticles (NiFNPs) have been indicated as a sustainable nanotechnology for biomedical, electronic, and nanoremediation fields. However, their release and presence in aquatic environments raise concerns about their potential effects on organisms and their offspring. Thus, the current study aimed to evaluate the effects of NiFNPs and nickel chloride (NiCl2) on young-to-adult freshwater snail Biomphalaria glabrata (mortality, growth, and fecundity) during 30 days of exposure, as well as the possible carry-over effects on the first generation (mortality, embryo development, hatching rate, heart rate, locomotor behavior, and touch sensitivity behavior) sampled after 7 and 28 days of parental exposure. B. glabrata adults were not significantly affected by the direct exposure to either Ni forms. Similarly, mortality, embryo development, and hatching rate of their offspring were not significantly impacted by parental exposure to either NiFNPs or NiCl2. Nevertheless, an increase in heart rate was observed in embryos sampled after 7-day parental exposure for both Ni forms compared with controls, whereas the opposite pattern was observed in embryos sampled after 28-day parental exposure. Further studies are needed to explain this contrasting outcome. In addition, parental exposure to NiFNPs produced snails with reduced thigmotaxis, which would make these snails more susceptible to predation in a NiFNPs-contaminated environment. The present study showed that parental exposure to sub-lethal concentrations of NiFNPs and NiCl2 can cause effects on unexposed offspring, highlighting the relevance of intergenerational studies in nanoecotoxicology.
The widespread use of veterinary pharmaceuticals in animal husbandry has raised growing concerns about detrimental effects to non-target organisms. In this study we examined the acute and chronic effects of three veterinary antibiotics (erythromycin, tylosin and sulfamethazine) in single, binary and tertiary mixtures to two species of cladocerans, Daphnia magna and Ceriodaphnia dubia, and to larvae of the midge, Chironomus dilutus. Acute median lethal concentrations (48-h LC50) ranged from 87 mg/L (sulfamethazine) to 566 mg/L (tylosin) for D. magna and 77 mg/L (sulfamethazine) to 444 mg/L (tylosin) for C. dubia. For the midge, 96-h LC50 values for each of the chemicals alone was 256 mg/L for erythromycin and > 1000 mg/L for tylosin and sulfamethazine. The 10-day EC50 values for D. magna reproduction ranged from 5.7 mg/L (sulfamethazine) to 193 mg/L (tylosin), while for C. dubia these values ranged from 2.4 mg/L (sulfamethazine) to 321 mg/L (tylosin). Effects on growth and survival of C. dilutus in 10-day bioassays were only observed for erythromycin and sulfamethazine, with EC50 values all greater than 200 mg/L. No chronic effects were observed for midges exposed to tylosin at concentrations up to 500 mg/L. Combining the antibiotics in mixture generally reduced their acute and chronic LC and EC50 values. The lowest EC50 value generated was 1 mg/L sulfamethazine for C. dubia reproduction in a 7-day bioassay with sulfamethazine and tylosin in combination. Still, toxic unit calculations indicated predominantly additive interactions between the three antibiotics. Overall, the effects concentrations generated were well above reported water concentrations, indicating these chemicals may present a low level of risk to the aquatic organisms assessed in this study.
Synthetic anthelmintics widely used in livestock production are largely excreted unchanged in faeces, where they can exert sublethal and lethal effects on non-target organisms such as dung beetles. Phytochemical compounds, including thymol (THY), have been proposed as environmentally compatible alternatives; however, information on their ecotoxicological safety across different dung beetle taxa remains limited. We assessed the sublethal effects of dietary thymol on Thorectes lusitanicus (Coleoptera: Geotrupidae), a flightless tunneller dung beetle considered functionally sensitive to veterinary drug residues. Antennal sensory responses were evaluated using electroantennography, and immune function was assessed by measuring haemolymph total protein content, phenoloxidase and prophenoloxidase activities. Ivermectin was included as a reference compound due to its well-documented ecotoxic effects on dung beetles. Thymol ingestion did not affect antennal olfactory responses or immune parameters across a wide range of concentrations, and no neurotoxic symptoms were observed. Significant inhibitory effects were detected only at concentrations substantially higher than thymol residues measured in cattle dung following dietary supplementation. In contrast, ivermectin significantly impaired olfactory function and induced clear neurotoxic symptoms. Overall, these results indicate that thymol is unlikely to cause ecotoxicologically relevant sublethal effects in tunneller dung beetles under the exposure scenarios evaluated. Our findings suggest that thymol-based phytochemical anthelmintics may represent environmentally compatible alternatives to conventional veterinary drugs.
Micro- and nanoplastic toxicity is a growing environmental concern, especially in aquatic ecosystems. This study investigates the acute and chronic effects of polypropylene microfibers (PP MFs), derived from artificially aged surgical face masks, on two aquatic species: the freshwater amphibian Xenopus laevis and the marine brittle star Ophiactis virens. Characterisation of the aged PP material revealed both microfibers (mean size: 21.7 ± 13.4 μm × 1.9 ± 0.8 μm) and nanofragments (mean diameter: 176 ± 28 nm), with a nano/micro abundance ratio of 4.3. X. laevis larvae ingested large quantities of PP MFs, resulting in near-complete gut obstruction, while juvenile O. virens did not show internal accumulation. Despite this, both species exhibited some sublethal effects, particularly at the behavioural level and at the highest tested dose (10 µg mL⁻¹). Indeed, X. laevis larvae reduced their swimming activity, whereas O. virens showed impaired righting ability. Moreover, X. laevis larvae grew significantly more than controls at all tested concentrations (0.1–10 µg mL⁻¹). No significant effect was observed at the cell-tissue level, except for a few cases of ultrastructural alteration in X. laevis intestinal epithelium. The LOEC values were 0.1 µg mL⁻¹ for X. laevis and 10 µg mL⁻¹ for O. virens; corresponding NOECs were < 0.1 and 1.0 µg mL⁻¹, respectively. These findings highlight species-specific responses, likely linked to ecological traits and life stage, and caution against generalizing toxicity outcomes across taxa. Overall, the study underscores the environmental legacy of COVID-19-related waste able to release a huge quantity of both micro- and nano-plastics with variable yet significant impacts on aquatic life.
Diflubenzuron (DFB) is a larvicide widely incorporated into pesticide product formulations (PPFs). In addition to the active ingredient (AI), PPFs contain inert substances and adjuvants that may interfere with the AI toxicity. This study aims to compare the embryotoxicity of a veterinary powder (VF; 3% DFB) and an agricultural water-soluble pellet (AF; 80% DFB) towards DFB, referred to as AI (purity > 99%). Zebrafish (Danio rerio) embryos were exposed to AI and both formulations at low (0.025 and 0.125 mg L− 1 of AI); intermediate (0.25 and 1.25 mg L− 1 of AI); and high (2.5 and 10 mg L− 1 of AI) concentrations, as well as a reconstituted water (fish medium) and DMSO (0.4% v/v) controls. Survival, hatching rates, pigmentation, and morphological biomarkers were monitored over 120 h post-fertilization (hpf). No significant effects on survival or hatching rates were observed. Morphological abnormalities, such as notochord deformities and yolk sac opacity, occurred at all concentrations, differing in frequency and intensity. AI showed stronger effects at lower and intermediate concentrations, whereas AF and VF exhibited stronger effects at higher concentrations. Oxygen consumption did not differ significantly from controls. Regarding morphometry, AF induced more pronounced alterations than both PPFs, mainly at intermediate and high concentrations, affecting sensory, physiological, skeletal, and muscle parameters. VF caused minor changes, AI showed no significant effects, and AF presented greater toxicity. AF caused an increase while AI and VF resulted in a slight decrease in body pigmentation. Our findings suggest that PPFs may enhance toxicity by increasing the AI solubility.
Understanding sublethal pesticide effects on aquatic organisms is important because behavioral impairment may occur before overt mortality and may influence ecological fitness. This study evaluated the behavioral and toxicological responses of fourth-instar Culiseta longiareolata larvae following nominal imidacloprid exposure using a dual-geotaxis bioassay. Larvae were identified morphologically and individually exposed to nominal concentrations of 0, 1, and 2 mg L⁻¹ imidacloprid under controlled laboratory conditions. Behavioral activity was recorded for 10 min following acclimation, and geotactic responses were quantified as negative geotaxis (time spent swimming upward or remaining near the surface) and positive geotaxis (time spent moving downward or remaining near the bottom). Acute toxicity was assessed separately after 24-hour exposure to nominal concentrations of 0, 0.5, 1, and 2 mg L⁻¹. Under control conditions, larvae exhibited predominantly surface-oriented behavior, spending approximately 75% of the observation period in negative geotaxis (p < 0.01). Imidacloprid exposure produced concentration-related behavioral changes characterized by reduced negative geotaxis and increased positive geotaxis at both tested concentrations (p < 0.05). Probit analysis estimated a 24-hour LC₅₀ of 1.349 mg L⁻¹, while exploratory polynomial modelling identified a geotactic equilibrium concentration of 0.523 mg L⁻¹, at which predicted time allocation between positive and negative geotaxis was equal. This value closely corresponded to the estimated LC₃₁ (0.519 mg L⁻¹). The findings demonstrate that dual-geotaxis measurements can detect measurable behavioral alterations under sublethal imidacloprid exposure and may provide a complementary endpoint to conventional lethality-based assessments in aquatic ecotoxicology. Although mechanistic pathways and analytical verification of exposure concentrations were not evaluated, the assay offers a practical framework for rapid behavioral screening of neuroactive contaminants.
Non-steroidal anti-inflammatory drugs (NSAIDs) belong to the most frequently detected pharmaceutical pollutants in aquatic ecosystems, raising growing concern about their effects on non-target primary producers. Unlike earlier reviews, based mainly on data collected before the year 2020, when environmental exposure levels were substantially lower, this work synthesizes research conducted over the last five years (2020-2025), a period that includes the SARS-CoV-2 pandemic. The pandemic was associated with a sharp global increase in the consumption of NSAIDs, resulting in their markedly elevated environmental loads. Consequently, the studies assessed in this review reflect plant and algal responses under significantly higher contamination pressures than those reported in pre-pandemic decades, offering a new perspective on their phytotoxic potential. A systematic literature search retrieved over 5,000 records, from which the most relevant experimental studies were selected for detailed evaluation. The compiled evidence demonstrates that NSAIDs adversely affect photosynthesis, induce ultrastructural damage to chloroplasts, and compromise mitochondrial respiration, including alterations in membrane potential and ATP production. Exposure to NSAIDs triggers oxidative stress responses, characterized by reactive oxygen species overproduction, lipid peroxidation, and variable changes in antioxidant enzyme activity. Beyond primary metabolism, numerous reports document disruptions in growth patterns, root system architecture, mineral balance, and secondary metabolite biosynthesis. By integrating the most up-to-date findings from a period of exceptionally intense pharmaceutical pollution, this review provides a novel and more realistic assessment of the ecological risks posed by NSAIDs. It underscores the urgency of developing stricter environmental quality standards and highlights key directions for future research under contemporary contamination scenarios.
Southern Brazil is a key agricultural region in South America, where wetland ecosystems are increasingly impacted by irrigated rice cultivation. Amphibians are particularly sensitive to environmental contamination due to their permeable skin and biphasic life cycle, making them effective bioindicators of ecosystem health. This landscape forms a mosaic of croplands and natural habitats, exposing wildlife to agrochemical contamination. In this study, we evaluated erythrocyte nuclear abnormalities (NAs) in the arboreal amphibian Dendropsophus sanborni and the aquatic amphibian Pseudis minuta, both inhabiting natural and agricultural wetlands in southern Brazil. Our results revealed significantly higher frequencies of NAs in individuals from agricultural environments across all evaluated biomarkers, indicating a generalized increase in genomic instability. Both micronuclei (MN) and nuclear abnormalities excluding MN (ENAs) increased in agricultural areas, reflecting different dimensions of genotoxic stress. Pseudis minuta consistently exhibited higher frequencies of abnormalities than D. sanborni and showed stronger responses to habitat type, highlighting the role of ecological traits and exposure pathways in modulating susceptibility to contaminants. Temporal variation was observed for several biomarkers, with higher frequencies occurring during periods coinciding with the onset of agricultural activities. These findings demonstrate that agricultural intensification promotes widespread cellular damage in wetland amphibians and emphasize the importance of integrating multiple biomarkers and species with contrasting ecological traits in biomonitoring programs. Such approaches are essential to improve the detection of sublethal effects of agrochemical exposure and to support conservation strategies in agricultural landscapes.
The house fly, Musca domestica (Linnaeus, 1758), is a major threat to public health and food safety due to its ability to transmit numerous pathogenic microorganisms. Despite global control efforts, populations remain abundant in residential areas, livestock facilities, and slaughterhouses, largely due to their high reproductive potential and widespread insecticide resistance. Continuous monitoring of resistance and its underlying mechanisms is therefore essential. In this study, toxicity bioassays were conducted on five strains collected from slaughterhouses using the feeding method. While permethrin, deltamethrin, and bendiocarb were ineffective, thiamethoxam showed variable susceptibility, and fipronil exhibited the highest efficacy. In addition, target-site mutations associated with resistance were screened in a total of 35 samples collected from slaughterhouses and residential areas. A high prevalence of T929I and L1014F mutations in the voltage-gated sodium channel (VGSC) and V260L, A316S, G342A/V, and F407Y mutations in acetylcholinesterase (AChE) - the target sites of pyrethroids and carbamates, respectively - was detected. In silico docking of bendiocarb on M. domestica AChE was conducted for the first time and largely confirmed the functional impact of ace mutations through reduced binding energies. Notably, the L1014H (VGSC) and G342V (AChE) mutations occurred exclusively in slaughterhouse samples, potentially indicating stronger local selection pressure than in residential areas. In contrast, the A301S mutation in the resistance to dieldrin (rdl) gene, the target site of fipronil, was absent from all samples. A haplotype network analysis of all available cytochrome c oxidase subunit I (COI) sequences from GenBank, combined with those generated in this study, revealed a predominant star-like haplotype with low overall genetic diversity, likely reflecting the species' high dispersal ability. Overall, these findings characterize the current resistance status of Turkish house flies and provide essential phenotypic and molecular data to support improved resistance management strategies.
Thiamethoxam (TMX) is a widely used neonicotinoid insecticide with high water solubility, which increases the likelihood of contamination in freshwater systems. Here, we assessed lethal and sublethal effects of TMX on the early life stages of the Neotropical Amazonian fish Astyanax bimaculatus. Two assays were performed: (i) embryonic exposure under static conditions (0, 0.05, 0.5, 5, and 50 mg/L; 200 embryos per treatment) and (ii) 96-h acute toxicity test on 1-day post-hatch larvae under semi-static conditions (0, 5, 25, and 50 mg/L; three aquaria of 100 larvae per treatment). During embryonic exposure, a visible coating over the chorion was observed at 5 and 50 mg/L, coinciding with both reduced normal hatching and increased larval deformities. The proportion of normally hatched larvae decreased from 97.5% in the control to 60.0% at 50 mg/L, while deformities increased to 15.5%, and unhatched embryos reached 24.5%. Post-hatch morphometry showed significant reductions in total length and yolk sac dimensions at concentrations ≥ 0.5 mg/L. In the larval assay, mortality increased in a dose-dependent manner, reaching mean values of 22.7%, 32.3%, and 64.0% at 5, 25, and 50 mg/L, respectively; the 96 h LC50 was 35.63 mg/L (95% CI: 27.83-43.44 mg/L). Overall, TMX impaired the survival and early development of A. bimaculatus, supporting the inclusion of early-life stage endpoints in the monitoring and risk assessment of Amazonian freshwater environments.
Agricultural intensification, driven by increasing food demand, is one of the main drivers of global biodiversity loss. Pesticides, including fungicides, may increase crop yield but pose substantial threats to the environment. However, our current knowledge on the effects of fungicides on biodiversity suffers from less research interest compared to other pesticides and a neglect of insect herbivores. We here investigate the effects of a commercially available, ready-to-use difenoconazole fungicide on a non-target insect, the butterfly Pieris napi, under controlled laboratory conditions. When being fed with fungicide-treated host plants, butterfly larvae showed a strongly reduced survival (15%) compared to controls (60%). Survival in larvae treated with the fungicide plus an insecticide was only 1%. Sublethal effects of the fungicide included prolonged development and reduced adult size. Our results indicate a surprisingly high toxicity of the tested fungicide formulation on P. napi. Based on the available literature, we speculate that triazole fungicides may be in general toxic to Lepidoptera and potentially other herbivorous insects. This study contributes to the growing evidence that fungicides may well be involved in the loss of insect biodiversity in agricultural landscapes at the global scale.
Rising environmental pollution poses a significant threat to bat populations worldwide, raising serious ecological and conservation concerns. Here, we present the first assessment of cytogenotoxic stress responses in cave-dwelling insectivorous bats from the karst island of Cat Ba in northern Vietnam, in relation to anthropogenic pollution. The study aimed to evaluate the association between exposure to heavy metals (HMs) and DNA damage, as well as blood alterations in bats, using minimally -invasive biomarkers. We applied an integrated approach combining three indicators: HM accumulation in guano (a hallmark of exposure), micronucleus (MN) frequency (a measure of genotoxicity), and the polychromatic-to-normochromatic erythrocyte (PCEs/NCES) ratio (a measure of cytotoxicity). Guano-derived cadmium (Cd) and lead (Pb) levels correlated strongly with genotoxic markers, confirming guano as a reliable indicator of HM contamination at the population level. Species- and site- specific cytogenotoxic responses to HM stress were manifested through the formation of MNs and the reduction of the PCEs/NCEs ratio, signifying the presence of DNA damage, suppression of bone marrow activity, and disruption of erythropoiesis. Combining guano chemistry with cytogenotoxic biomarkers provides a sensitive and non-invasive tool for monitoring environmental stress in bat populations in karst ecosystems.
The methods used in animal studies can influence organism responses in subtle ways. Toxicology studies conduct exposures on organisms individually or in groups, dependant on the goals of the study. It is important that the subtle influences of these choices in methodology are understood so that cross-study comparisons can be made within the context that the data was generated in. This study compared differences in toxicity and organism physiology in Daphnia magna exposed to ultraviolet filters across five generations between individual and group exposure scenarios. The baseline mortality of daphnids was doubled in group exposures, accompanied by an increasing number of males over subsequent generations to a maximum of 10% of the population, as well as delayed timing of maturation and brood frequency compared to individual organisms exposed with the same ratio of food and water. These differences were largely independent of chemical treatment, indicating that the presence of conspecifics influences the responses of D. magna across a variety of physiological endpoints. This study highlights the importance of experimental design when comparing toxicity data across studies so that confounding factors such as conspecific presence do not lead to inaccurate comparisons of data obtained across studies using differing methodologies.
The global decline of pollinators threatens ecosystem stability and food security. Bees are particularly affected by agricultural insecticides, with neonicotinoids and pyrethroids being among the most widely used classes. While their individual sublethal effects are documented, the consequences of combined exposures remain poorly understood. This study evaluated the isolated and combined effects of field-realistic oral doses of Imidacloprid (0.5 ng/bee) and Deltamethrin (2 ng/bee) on Africanized honey bees (Apis mellifera) of southern Brazil. We quantified grooming, wing fanning, feeding and locomotion (walking time, distance and speed) under laboratory conditions. Imidacloprid caused a strong elevation in grooming behavior (8.64-fold) and reduced both walking distance (-308 cm) and speed (-1.04 cm·s⁻¹). Deltamethrin increased grooming to a lesser extent (2.96-fold) without affecting any locomotion capability. Combined exposure resulted in non-additive effects, with grooming activity reaching levels similar to those of Imidacloprid alone (7.79-fold). However, unlike Imidacloprid, the mixture caused no locomotor deficits, which contrasts with the additive or synergistic interactions commonly reported for insecticide mixtures. No treatment affected syrup consumption or mortality over a 24 h period. These results demonstrate that neonicotinoids and pyrethroids disrupt honey bee behavior through distinct pathways and that mixture effects cannot be predicted from single-compound responses. Incorporating behavioral endpoints and mixture toxicology into risk assessments is essential for improving pesticide-pollinator dynamics and protection strategies.
Consumers are ingesting and excreting extraordinary amounts of non-nutritive sweeteners (NSs) which, because they are not metabolized, enter surface- and groundwater systems. Furthermore, agricultural animal feed often contains NSs that become concentrated in manure and subsequently spread on fields as fertilizer. With both fertilizer and irrigation waters introducing NSs into terrestrial soils, NSs are now classified as a contaminant of emerging concern, highlighting the need to study their potential ecotoxicological effects. Here, we investigated the impact of sucralose on the gas exchange, chlorophyll content, and floral color patterns of three North American wildflowers: black-eyed Susans (Rudbeckia hirta), cardinal flower (Lobelia cardinalis), and purple cone flowers (Echinacea purpurea). Even an environmentally-miniscule concentration of sucralose (10 μg L-1) resulted in altered gas exchange, lower water use efficiency, and significantly lower chlorophyll concentrations in most of these species. Furthermore, sucralose altered the flowering hue of R. hirta, suggesting that NSs might impact plant-pollinator interactions. Our results suggest that the ever-increasing prevalence of NSs in our surface and groundwater systems might pose a significant threat to agricultural and ecological systems by altering plant physiology and flower morphology.
Zinc oxide nanoparticles (ZnO-NPs) are widely used engineered nanomaterials increasingly present in freshwater ecosystems, yet their effects on amphibians remain poorly understood. Amphibians are ecologically important and highly sensitive to contaminants, making them valuable bioindicators. This study provides the first integrated assessment of ZnO-NP effects on the European toad (Bufo bufo, Gosner stages 26–27), combining biochemical, endocrine, and histological endpoints. Tadpoles were exposed for seven days to sub lethal ZnO-NP concentrations (0.1, 1.0, and 10 mg/L) under controlled laboratory conditions, then maintained in clean water until metamorphosis to evaluate survival, growth, developmental progression, and tissue integrity. Exposure induced ROS-mediated oxidative stress, evidenced by increased SOD and CAT activities and elevated malondialdehyde levels, while corticosterone elevation revealed systemic endocrine disruption. Histological analyses showed dose-dependent damage in gills, liver, eyes, and limb buds, with limb buds and gills exhibiting the highest sensitivity. These combined morphological and physiological impairments led to developmental delays, stage-specific mortality peaks, and arrested metamorphosis, highlighting critical windows of larval vulnerability. Our findings reveal a mechanistic pathway linking oxidative stress, endocrine disruption, and tissue damage and underscore the importance of integrating species-specific physiological and morphological responses in ecological risk assessments of nanoparticles.
This study focused on the exposure of a terrestrial raptor, the peregrine falcon (Falco peregrinus), in the United Kingdom. In contrast to inland areas, peregrine falcons in coastal areas of North Cornwall, South-west England, have recently declined despite a decreasing trend in environmental legacy organic contaminants. Exposure to per- and polyfluoroalkyl substances (PFAS) is suspected to contribute to one of the causes of this decline. However, unlike studies on aquatic birds, research on PFAS exposure of terrestrial predatory birds remains limited, particularly in British wild birds. To fill this knowledge gap, we have measured PFAS burdens in peregrine eggs from different English areas and compared them with stable isotope and eggshell index values.Our results showed that long-chain perfluoroalkyl acids were predominantly detected in peregrine eggs. Perfluorooctane sulfonyl acid (PFOS), perfluorohexanesulfonic acid (PFHxS), and perfluorooctanoic acid (PFOA) residues significantly differed among counties: PFOS and PFHxS residues were significantly higher in eggs from Devon, the study area around urban settlements, than in Cornwall. PFOA residues were significantly higher in Lancashire, an inland study area, than in Devon. Several perfluoroalkyl carboxylic acid residues showed significant and negative correlations with δ13C in eggs, suggesting that the sources of these PFAS might come from terrestrial habitats. No significant relationship was observed between eggshell index and PFAS residues. Given the variation in PFAS exposure among areas, it remains challenging to determine the impact of PFAS on the Cornwall peregrine population. Further studies are needed to fill these knowledge gaps.
Copper (Cu) is a widespread aquatic contaminant, but the integrated intestinal responses of adult zebrafish to sub-chronic waterborne Cu exposure remain insufficiently characterized. Adult zebrafish (initial body weight, 0.29 ± 0.02 g; total length, 3.11 ± 0.15 cm) were exposed for 14 days to nominal Cu concentrations of 0, 0.04, 0.08, and 0.16 mg/L, and terminal growth, intestinal Cu accumulation, histopathology, and gut microbiota were evaluated. Compared with the control, terminal body weight decreased significantly in the medium- and high-exposure groups by 7.07% and 6.86%, respectively (P < 0.05), whereas body length was not significantly affected. Intestinal Cu burden increased markedly with exposure concentration. Histological analysis revealed epithelial disruption, villus/fold injury, vacuolization, necrosis, edema, and inflammatory cell infiltration, with more severe lesions in the medium- and high-exposure groups. 16 S rRNA sequencing indicated Cu-associated restructuring of the gut microbiota. Richness indices (ACE and Chao1) decreased in the medium- and high-exposure groups, whereas Shannon and Simpson indices showed a non-monotonic response. At the genus level, Cetobacterium increased under low and medium Cu exposure but declined under high exposure, Lactococcus was mainly enriched in the medium-exposure group, and Pseudomonas decreased across Cu-exposed groups. Overall, sub-chronic Cu exposure induced intestinal Cu accumulation, tissue injury, and gut microbial dysbiosis in adult zebrafish, supporting the intestine as a sensitive target of Cu toxicity.
Pyrethroid insecticides are ubiquitous in waterways throughout the United States. Consequently, species have evolved resistance to these insecticides via receptor site mutations with unknown impacts to their fitness. The goal of this study was to determine if pyrethroid-resistant Hyalella azteca populations (Escondido and Mosher) exhibited disrupted phototaxis compared to a non-resistant population. We tested phototactic response to determine the sensitivity of H. azteca to chemicals that cause neurobehavioral impacts. H. azteca were exposed to non-dosed, permethrin (pyrethroid), and fipronil (phenylpyrazole) treatments 24 h before assessing phototaxis using light stimulus. Each population was genotyped for mutations in the voltage-gated sodium channel (VGSC) and the γ-aminobutyric acid (GABA) receptor. Non-resistant H. azteca had a faster response to light stimulus than resistant populations following the non-dosed and fipronil-dosed exposures. When exposed to pyrethroids, the Escondido population responded more rapidly than the non-resistant population. Genotyping results revealed all populations were wild-type for rdl, the gene encoding the GABA-gated chloride channel and the target for phenylpyrazole insecticides. In addition, the Mosher population shifted from homozygous for the L925I substitution in the VGSC gene (vgsc) to a relatively weaker I936F for pyrethroid resistance. The exact cause in the reduction in negative phototaxis and general fitness is unknown but may stem from reduced protein efficiency from the vgsc mutations or possible results of genetic bottlenecking, hence reducing genetic diversity. Benefits of adaptation may be limited to improved survivorship under harsh conditions of insecticide exposure but at a cost to overall fitness including phototactic behavior.