Long-term exposure of the isopod Porcellionides pruinosus to nickel: Costs in the energy budget and detoxification enzymes

Antioxidant enzyme activity and pathophysiological consequences in the sludge worm Tubifex tubifex under acute and sub-lethal exposures to the fungicide Tilt ®

This study aimed to evaluate the effects of propiconazole on the tubificid segmented worm, Tubifex tubifex. The animals were exposed to various concentrations of propiconazole for 96 h to assess the acute effect of this fungicide and for subacute level animals were exposed for 14 days with 10% and 20% of the 96 h LC50 value (0.211 and 0.422 mg/l, respectively). The 96 h LC50 value was determined to be 2.110 mg/l, and sublethal propiconazole concentrations caused significant changes in the oxidative stress enzymes. When compared to control organisms, superoxide dismutase (SOD) and catalase (CAT) activity first decreases and then significantly increases on days 7 and 14. However, GST activity decreases and MDA concentration rises in a concentration- and time-dependent manner throughout the exposure period. In addition, the impacts of propiconazole on Tubifex tubifex were characterized and depicted using a correlation matrix and an integrated biomarker response (IBR) assessment. These findings suggest that exposure to this fungicide distorts the survivability and behavioral response in Tubifex tubifex at the acute level. In addition, it modulates changes in oxidative stress enzymes at the sublethal level. Furthermore, the species sensitivity distribution curve indicates that this tubificid worm has a high risk of survival in the presence of the fungicide propiconazole in aquatic ecosystems.

Copper-contaminated soil compromises thermal performance in the springtail Folsomia candida (Collembola)

The widespread agricultural and industrial emissions of copper-based chemicals have increased copper levels in soils worldwide. Copper contamination can cause a range of toxic effects on soil animals and influence thermal tolerance. However, toxic effects are commonly investigated using simple endpoints (e.g., mortality) and acute tests. Thus, how organisms respond to ecological realistic sub-lethal and chronic exposures across the entire thermal scope of an organism is not known. In this study, we investigated the effects of copper exposure on the thermal performance of a springtail (Folsomia candida), regarding its survival, individual growth, population growth, and the composition of membrane phospholipid fatty acids. Folsomia candida (Collembola) is a typical representative of soil arthropods and a model organism that has been widely used for ecotoxicological studies. In a full-factorial soil microcosm experiment, springtails were exposed to three levels of copper (ca. 17 (control), 436, and 1629 mg/kg dry soil) and ten temperatures from 0 to 30 °C. Results showed that three-week copper exposure at temperatures below 15 °C and above 26 °C negatively influenced the springtail survival. The body growth was significantly lower for the springtails in high-dose copper soils at temperatures above 24 °C. A high copper level reduced the number of juveniles by 50 %, thereby impairing population growth. Both temperature and copper exposure significantly impacted membrane properties. Our results indicated that high-dose copper exposure compromised the tolerance to suboptimal temperatures and decreased maximal performance, whereas medium copper exposure partially reduced the performance at suboptimal temperatures. Overall, copper contamination reduced the thermal tolerance of springtails at suboptimal temperatures, probably by interfering with membrane homeoviscous adaptation. Our results show that soil organisms living in copper-contaminated areas might be more sensitive to thermally stressful periods.

Sub-lethal acute effects of environmental concentrations of inorganic mercury on hematological and biochemical parameters in walking catfish, Clarias batrachus

The acute toxicity of mercury to the air-breathing fish Clarias batrachus (Linn.) was determined in this study using hematological (including hemoglobin, hematocrit, total erythrocyte count, total leukocyte count, and mean corpuscular hemoglobin concentration) and biochemical (including total serum protein, serum glucose, triglyceride, cholesterol, albumin) biomarkers at predetermined exposure concentrations (0.069 and 0.139 mg/L). Although significant differences were observed between exposure groups for all hematological and biochemical variables, a distinctive reduction in hemoglobin levels, hematocrit, and total erythrocyte count in the mercury-exposed fish compared to the control was observed from 24 h-96 h. Similarly, marked differences in serum globulin, total serum protein and cholesterol levels were observed across exposure groups from 24 h-96 h. While the marked hematological responses strongly suggestive of toxicant-related anemia, the marked biochemical responses suggest immune-modulation and metabolic disruption. The magnitude of toxic effects under graded toxicant exposures for weighted scores of combined biomarker response index (IBR) indicated an approximately 3-fold deterioration in overall health of mercury-exposed fish compared to control group. Depictions of hematological and biochemical effects in hardy species like Clarias batrachus indicate an imminent onset of anemia, immune-modulation and metabolic disruption within 24hs of exposure to inorganic mercury. Such observations for portends greater deleterious effects to less hardy aquatic biota under acute inorganic mercury environmental exposures.

Combined effects of global warming and chlorpyrifos exposure on the annual fish Nothobranchius furzeri

Global warming and environmental pollution threaten aquatic ecosystems. While interactive effects between both stressors can have more than additive consequences, these remain poorly studied for most taxa. Especially chronic exposure trials with vertebrates are scarce due to the high time- and monetary costs of such studies. We use the recently-established fish model Nothobranchius furzeri to assess the separate and combined effects of exposure to the pesticide chlorpyrifos (at 2 µg/L and 4 µg/L) and a 2 °C temperature increase. We performed a full life-cycle assessment to evaluate fitness-related endpoints including survival, total body length, maturation time, fecundity, critical thermal maximum (CTmax) and locomotor activity. Exposure to 4 µg/L chlorpyrifos slowed down male maturation, reduced fecundity and impaired growth of the fish. While the temperature increase did not affect any of the measured endpoints on its own, the combination of exposure to 2 µg/L CPF with an increase of 2 °C reduced growth and severely reduced fecundity, with almost no offspring production. Together, these findings suggest that climate change may exacerbate the impact of environmental pollution, and that interactive effects of chronic exposure to multiple stressors should be considered to predict how populations will be affected by ongoing global change.

Mechanistic insights to lactic and formic acid toxicity on benthic oligochaete worm Tubifex tubifex

Lactic and formic acid are two commonly found monocarboxylic organic acids. Lactic acid is discharged into the water bodies as acidic industrial effluent from the food, cosmetic, chemical, and pharmaceutical industries, whereas formic acid is discharged from various paper, leather tanning, and textile processing industries. The present study investigated the toxicity of both organic acids upon the benthic oligochaete worm Tubifex tubifex. The 96-h median lethal concentration (LC₅₀) values for lactic and formic acid are determined as 143.81 mg/l and 57.99 mg/l respectively. The effects of two sublethal concentrations (10% and 30% of 96 h LC₅₀) of these acids on differential expression of oxidative stress enzymes are investigated. The comparative analysis of acute toxicity demonstrates that formic acid exposure is more detrimental to T. tubifex than lactic acid. The in silico structural analysis predicts that formic acid can interact with cytochrome c oxidase of the electron transport system and thereby inhibits its functionality and induces reactive oxygen species production. Integrated biomarker response (IBR) analysis illustrates that overall oxidative stress of formic acid to T. tubifex is significantly higher than that of lactic acid, which supports the structural analysis. It is concluded from this study that toxicokinetic-toxicodynamic and species sensitivity distributions studies are helpful for ecological risk management of environmental toxicants.

The effects of different temperatures in mercury toxicity to the terrestrial isopod Porcellionides pruinosus

Climate changes and metal contamination are pervasive stressors for soil ecosystems. Mercury (Hg), one of the most toxic metals, has been reported to interact with temperature. However, compared to aquatic biota, little is known about how temperature affects Hg toxicity and bioaccumulation to soil organisms. Here, toxicity and bioaccumulation experiments were replicated at 15 °C, 20 °C, and 25 °C to understand how sub-optimal temperatures affect the toxicokinetics and toxicodynamics of Hg via soil. Genotoxicity and energy reserves were also assessed to disclose potential trade-offs in life-history traits. Results underpin the complexity of temperature-Hg interactions. Survival was determined mainly by toxicokinetics, but toxicodynamics also played a significant role in defining survival probability during early stages. The processes determining survival probability were faster at 25 °C: General Unified Threshold of Survival (GUTS) model identified an earlier/steeper decline in survival, compared to 20 °C or 15 °C, but it also approached the threshold faster. Despite potentiation of Hg genotoxicity, temperature promoted faster detoxification, either increasing toxicokinetics rates or damage repair mechanisms. This metabolism-driven increase in detoxification led to higher depletion of energy reserves and likely triggered stress response pathways. This work emphasized the need for comprehensive experimental approaches that can integrate the multiple processes involved in temperature-metal interactions.

Antioxidant enzyme activity and pathophysiological responses in the freshwater walking catfish, Clarias batrachus Linn under sub-chronic and chronic exposures to the neonicotinoid, Thiamethoxam®

The hydrophilic nature and resultant persistence of neonicotinoids in aquatic systems increase the exposure duration for non-target organisms. The sublethal toxicity of the neonicotinoid Thiamethoxam® spanning sub-chronic and chronic durations was investigated in Clarias batrachus, a non-target freshwater fish species. 96 h LC₅₀ value of Thiamethoxam® on Clarias batrachus was 138.60 mg L^-1. Pre-determined exposure concentrations of Thiamethoxam® (6.93 and 13.86 mg L^-1) were used and effects were assessed at days 15, 30, and 45 exposure intervals. Biomarker effects were evaluated using antioxidant enzyme responses (CAT, SOD) neurotransmission (acetylcholinesterase activity), haematological and serum biochemistry changes (including haemoglobin content, total erythrocyte count, and serum albumin total leukocyte count, total serum protein, serum globulin, triglyceride, cholesterol, high-density lipoprotein, very low-density lipoprotein, low-density lipoprotein, phospholipid, and total serum glucose), histopathological alterations (gill and liver). Thiamethoxam®-exposed fish showed a marked reduction in haemoglobin content, total erythrocyte count, and serum albumin levels compared to control fish. Similarly, gill and liver antioxidant enzyme activity (CAT, SOD) and neurotransmission (acetylcholinesterase) also showed altered responses between sub-chronic exposure on day-15 and chronic responses on day-45. Histopathological observations in gill tissue revealed alterations ranging from vacuolation, hypertrophy, disruption of primary lamellar architecture, haemorrhage, the fusion of secondary lamella, and sloughing of outer epithelia. For liver tissue of exposed fish histopathological observations included increased sinusoidal spaces (ISS), necrosis of hepatocytes (NOH), nuclear degeneration (ND), disruption of architecture (DOA), macrophage infiltration of the central vein, vacuolation (V), hypertrophied hepatocytes, and haemorrhages. The gradients of toxic responses across exposure concentrations and depictions of impaired fish health with increasing thiamethoxam® exposure duration portend lowered physiological capacity for survival in the wild.

Effects of 2,4,6-Trichlorophenol on Clarias batrachus: a biomarkers approach

2,4,6-Trichlorophenol (2,4,6-TCP) is a common waste among the resulting chlorophenols generated in the production of common products classified as an extremely toxic, mutagenic, carcinogenic and highly persistent xenobiotic in the environment. To evaluate the impact of 2,4,6-TCP in aquatic systems, the catfish species Clarias batrachus has been selected to test its toxicity due to its high market value and consumption in India. Here is presented the impact of this compound on different physiological parameters of fish: haematological parameters (haemoglobin, total erythrocyte count, total leucocyte count and mean corpuscular haemoglobin), biochemical parameters (total serum protein and total serum glucose), growth and reproductive parameters (condition factor, hepatosomatic index, maturity index, specific growth rate, growth hormone, 17β-estradiol and testosterone), exposed to two concentrations of 2,4,6-TCP (0.5 mg/L and 1 mg/L - 1/10th and 1/20th of the LC₅₀) for a period of 15, 30 and 45 days. The results showed that C. batrachus even when exposed to the lower concentration (0.5 mg/L) for the shortest time (15 days) negatively impacted the organism in all the assessed parameters. This was highlighted by the Integrated Biomarker Response index (IBR), showing worse scores for the treatments (up to 20 × worse than the control). This work highlights the importance of continued research on the impact of 2,4,6-TCP, on an important commercial, supported by the high environmental persistence of this compound that can reach the same range of tested concentrations.

Pesticide sensitivity of Nothobranchius neumanni, a temporary pond predator with a non-generic life-history

Pesticides are crucial to improve agricultural productivity, but often adversely affect surrounding aquatic systems and their fauna. To determine the environmental risk of pesticides, routine ecotoxicological tests are performed on several organisms, including standard fish models. However, these typically do not include fish species from variable habitats and with non-generic life-histories. In particular, inhabitants from temporary ponds such as annual killifish are conventionally understood to be resilient to natural stressors which could translate to higher pesticide resistance or, alternatively, trade-off with their resistance to pesticides and render them more sensitive than classic fish models. Using standard exposure tests, we assessed short-term toxicity effects of two commonly used pesticides, Roundup and cypermethrin, on the annual killifish Nothobranchius neumanni, and compared its sensitivity with that of classic fish models. For Roundup, we found a 72 h-LC₅₀ of 1.79 ± 0.11 mg/L, which is lower than the values reported for zebrafish, medaka, fathead minnow and rainbow trout, suggesting that N. neumanni is more sensitive to the compound. The opposite was true for cypermethrin, with a 72 h-LC₅₀ of 0.27 ± 0.03 mg/L. However, these LC₅₀-values do not deviate strongly from those reported for other fish species, supporting earlier findings in the congeneric N. furzeri that the sensitivity of annual killifish to pollutants is similar to that of classic fish models despite their assumed robustness to environmental stress.

Integrated multi-biomarker responses of juvenile rainbow trout (Oncorhynchus mykiss) to an environmentally relevant pharmaceutical mixture

Pharmaceuticals are emerging pollutants of concern for aquatic ecosystems where they are occurring in complex mixtures. In the present study, the chronic toxicity of an environmentally relevant pharmaceutical mixture on juvenile rainbow trout (Oncorhynchus mykiss) was investigated. Five pharmaceuticals (paracetamol, carbamazepine, diclofenac, naproxen and irbesartan) were selected based on their detection frequency and concentration levels in the Meuse river (Belgium). Fish were exposed for 42 days to three different concentrations of the mixture, the median one detected in the Meuse river, 10-times and 100-times this concentration. Effects on the nervous, immune, antioxidant, and detoxification systems were evaluated throughout the exposure period and their response standardized using the Integrated Biomarker Response (IBRv2) index. IBRv2 scores increased over time in the fish exposed to the highest concentration. After 42 days, fish exposed to the highest concentration displayed significantly higher levels in lysozyme activity (p < 0.01). The mixture also caused significant changes in brain serotonin turnover (p < 0.05). In short, our results indicate that the subchronic waterborne exposure to a pharmaceutical mixture commonly occurring in freshwater ecosystems may affect the neuroendocrine and immune systems of juvenile rainbow trout.

DNA damage in Spodoptera exigua after multigenerational cadmium exposure - A trade-off between genome stability and adaptation

Human activity is a serious cause of extensive changes in the environment and a constant reason for the emergence of new stress factors. Thus, to survive and reproduce, organisms must constantly implement a program of adaptation to continuously changing conditions. The research presented here is focused on tracking slow changes occurring in Spodoptera exigua (Lepidoptera: Noctuidae) caused by multigenerational exposure to sub-lethal cadmium doses. The insects received food containing cadmium at concentrations of 5, 11, 22 and 44 μg per g of dry mass of food. The level of DNA stability was monitored by a comet assay in subsequent generations up to the 36th generation. In the first three generations, the level of DNA damage was high, especially in the groups receiving higher doses of cadmium in the diet. In the fourth generation, a significant reduction in the level of DNA damage was observed, which could indicate that the desired stability of the genome was achieved. Surprisingly, however, in subsequent generations, an alternating increase and decrease was found in DNA stability. The observed cycles of changing DNA stability were longer lasting in insects consuming food with a lower Cd content. Thus, a transient reduction in genome stability can be perceived as an opportunity to increase the number of genotypes that undergo selection. This phenomenon occurs faster if the severity of the stress factor is high but is low enough to allow the population to survive.

Impacts of nanoplastics on bivalve: Fluorescence tracing of organ accumulation, oxidative stress and damage

The outcomes of this research offer novel insights into the toxic effects of nanoparticles (i.e., nanoplastics or other nanomaterials) on the benthos. Herein, this study aimed to evaluate the accumulation pathway, distribution characteristics and potential biotoxicity of polystyrene nanoplastics in C. fluminea. The results revealed that nanoplastics could accumulate in the mantle through adherence, in the visceral mass through ingestion and in the gill through respiration. The gill, intestine and stomach were the main accumulation organs for nanoplastics. The aggregation of nanoplastics was observed in C. fluminea, which may exacerbate their biotoxicity. Moreover, oxidative stress was observed in the visceral mass, gill and mantle. Liver damage, neurotoxicity and intestinal inflammation were caused by imbalance in the antioxidation system. Analysis of IBR values showed that the visceral mass had a more effective response to oxidative stress than the gill and mantle after exposure to nanoplastics.

Multiple-Biomarker Approach in a Commercial Marine Scallop from San Jose gulf (Patagonia, Argentina) for Health Status Assessment

The health status of the commercial Tehuelche scallop Aequipecten tehuelchus from San Román and El Riacho in San José gulf (Patagonia, Argentina) was evaluated through biomarkers widely used in ecotoxicological applications. Natural levels of arsenic (As) and cadmium (Cd) were measured to determine their potential relationships with fluctuations of several oxidative stress biomarkers in the scallop. Oxidative biomarkers, such as catalase (CAT), glutathione S-transferase (GST), superoxide dismutase (SOD), metallothioneins (MT), reactive oxygen species (ROS), α-tocopherol (α-T), and lipid peroxidation (LPO) through thiobarbituric acid reactive substances (TBARS) and lipid radical (LR^∙), were measured in gills, digestive gland, and muscle of Tehuelche scallop in winter (August 2015) and summer (January 2016). Levels of As and Cd and of most of the biomarkers (SOD, ROS, TBARS, and LR^∙) showed strong seasonal variability in the three tissues. In general, the highest values were recorded in digestive gland. The Integrated Biomarker Response index indicated that the most stressed condition of A. tehuelchus was in summer in San Román. Additionally, the Integrated Biomarker Response index showed a strong relationship among tissues and As and Cd accumulation. This kind of approach could be used as an integrated tool to identify the health status of scallop A. tehuelchus from San José gulf.

Protective role of zinc in Spodoptera exigua larvae under 135-generational cadmium exposure

The aim of this study was to investigate whether zinc supplementation modulates cadmium toxicity in the beet armyworm Spodoptera exigua selected for 135 generations towards cadmium tolerance. To achieve this, larvae originating from three laboratory populations of S. exigua (control strain - C; cadmium-intoxicated for 135 generations strain - Cd, and control strain intoxicated with Cd for 1 generation - CCd) were additionally exposed to zinc in three concentrations (Zn1, 400 μg Zn·g^-1 dry mass of food; Zn2; 200 μg Zn·g^-1 dry mass of food; Zn3, 100 μg Zn·g^-1 dry mass of food). As the markers of toxicity, a life history traits (the duration of L4 and L5 stages), cellular (DNA damage indices) and biochemical parameters (ADP/ATP ratio and ATP and HSP70 concentrations) were chosen. The duration of larval stages of Zn supplemented larvae was prolonged, while cellular and biochemical indicators, in general, appeared to be lower in comparison to the insects from respective reference groups in each laboratory populations. Moreover, the range of the differences depended on zinc concentration in food. We can suspect that zinc supplementation contributed to the protection of S. exigua individuals against negative effects of cadmium intoxication, probably at the cost of growth rate. Significant differences in the response pattern between insects from different laboratory populations indicate that the influence of additional stress factors is dependent on the overall condition of animals and their previous adaptation to other stressors.

Unravelling the molecular mechanisms of nickel in woodlice

During the last few years, there has been an alarming increase in the amount of nickel (Ni) being released into the environment, primarily due to its use in the production of stainless steel but also from other sources such as batteries manufacturing and consequent disposal. The established biotic ligand models provide precise estimates for Ni bioavailability, in contrast, studies describing the mechanisms underpinning toxicological effect of Ni are scarce. This study exploits RNA-seq to determine the transcriptomic responses of isopods using Porcellionides pruinosus as an example of a terrestrial metal-resistant woodlouse. Furthermore, the recently proposed model for Ni adverse outcome pathways (Ni-AOP) presents an unprecedented opportunity to fit isopod responses to Ni toxicity and define Porcellionides pruinosus as a metalomic model. Prior to this study, P. pruinosus represented an important environmental sentinel, though lacking genetic/omic data. The reference transcriptome generated here thus represents a major advance and a novel resource. A detailed annotation of the transcripts obtained is presented together with the homology to genes/gene products from Metazoan and Arthropoda phylum, Gene Ontology (GO) classification, clusters of orthologous groups (COG) and assignment to KEGG metabolic pathways. The differential gene expression comparison was determined in response to nickel (Ni) exposure and used to derive the enriched pathways and processes. It revealed a significant impact on ion trafficking and storage, oxidative stress, neurotoxicity, reproduction impairment, genetics and epigenetics. Many of the processes observed support the current Ni-AOP although the data highlights that the current model can be improved by including epigenetic endpoints, which represents key chronic risks under a scenario of Ni toxicity.

Energy reserves and respiration rate in the earthworm Eisenia andrei after exposure to zinc in nanoparticle or ionic form

The energy budget is an indicator of an organism's overall condition. Changes in energy reserves and/or energy consumption have been used as biomarkers of toxic stress. To understand the effects of different forms and concentrations of Zn and the costs of effective Zn regulation by the earthworm Eisenia andrei, we performed a toxicokinetic experiment in which individuals were sampled over time to determine the available energy reserves (total carbohydrate, protein, and lipid content), energy consumption (measured at the cellular level and as the whole-animal respiration rate), and internal Zn concentration. The earthworms were exposed to ZnCl2 or zinc nanoparticles (ZnO-NPs) in Lufa 2.2 soil for 21 days (contamination phase), followed by 14 days of elimination in clean soil (decontamination phase). Carbohydrates were the only energy reserves with significantly lower levels following ZnO-NP 1000 treatment than following other treatments (p ≤ 0.00001) in the contamination phase. The total available energy reserves and protein content did not differ among treatments, but a significant effect of exposure time was observed (p ≤ 0.0001). Exposure to Zn (both ions and NPs) increased energy consumption at the cellular level, reflecting the high energy demand of the stress response. The results indicated that E. andrei can regulate internal Zn concentrations efficiently, regardless of form or concentration, without considerable impact on energy reserves or respiration rate.

Seawater acidification increases copper toxicity: A multi-biomarker approach with a key marine invertebrate, the Pacific Oyster Crassostrea gigas

Ocean acidification (OA) has been found to increase the release of free Cu²⁺ in seawater. However, only a handful of studies have investigated the influence of OA on Cu accumulation and cellular toxicity in bivalve species. In this study, Pacific oysters, Crassostrea gigas, were exposed to 25 μg/L Cu²⁺ at three pH levels (8.1, 7.8 and 7.6) for 14 and 28 days. Physiological and histopathological parameters [(clearance rate (CR), respiration rate (RR), histopathological damage and condition index (CI)), oxidative stress and neurotoxicity biomarkers [superoxide dismutase (SOD) and glutathione transferase (GST) activities, lipid peroxidation (LPO) and acetylcholinesterase (AChE) activity], combined with glycolytic enzyme activities [pyruvate kinase (PK) and hexokinase (HK)] were investigated in C. gigas. The bioconcentration of Cu was increased in soft tissues of Cu-exposed oysters under OA. Our results suggest that both OA and Cu could lead to physiological disturbance, oxidative stress, cellular damage, disturbance in energy metabolism and neurotoxicity in oysters. The inhibited CR, increased glycolytic enzymes activities and decreased CI suggested that the energy metabolism strategy adopted by oysters was not sustainable in the long term. Furthermore, integrated biomarker response (IBR) results found that OA and Cu exposure lead to severe stress to oysters, and co-exposure was the most stressful condition. Results from this study highlight the need to include OA in future environmental assessments of pollutants and hazardous materials to better elucidate the risks of those environmental perturbations.

Effects of Multi-Component Mixtures from Sewage Treatment Plant Effluent on Common Carp (Cyprinus carpio) under Fully Realistic Condition

This study characterized changes in biomarker responses in common carp (Cyprinus carpio) upon exposure to effluent water discharged from a sewage treatment plant (STP) under real conditions. Fish were exposed to contamination in Cezarka pond, which receives all of its water input from the STP in the town of Vodnany, Czech Republic. Five sampling events were performed at day 0, 30, 90, 180, and 360 starting in April 2015. In total, 62 pharmaceutical and personal care products (PPCPs) were detected in the polar organic chemical integrative sampler. Compared to a control pond, the total concentration of PPCPs was 45, 16, 7, and 7 times higher in Cezarka pond at day 30, 90, 180, and 360, respectively. The result of oxidative stress and antioxidant enzyme biomarkers indicated alterations in the liver and intestine tissues of fish from Cezarka pond at day 30 and 360, respectively. High plasma vitellogenin levels were observed in both exposed females (180 and 360 days) and males (360 days) compared with their respective controls. However, only exposed female fish had higher vitellogenin mRNA expression than the control fish in these periods. Exposed female fish showed irregular structure of the ovary with scattered oocytes, which further developed to a vitellogenic stage at day 360. Low white blood cell levels were indicated in all exposed fish. Despite numerous alterations in exposed fish, favorable ecological conditions including high availability of food resulted in a better overall condition of the exposed fish after 1 year of exposure compared to the controls.

Living in a multi-stressors environment: An integrated biomarker approach to assess the ecotoxicological response of meagre (Argyrosomus regius) to venlafaxine, warming and acidification

Pharmaceuticals, such as the antidepressant venlafaxine (VFX), have been frequently detected in coastal waters and marine biota, and there is a growing body of evidence that these pollutants can be toxic to non-target marine biota, even at low concentrations. Alongside, climate change effects (e.g. warming and acidification) can also affect marine species' physiological fitness and, consequently, compromising their ability to cope with the presence of pollutants. Yet, information regarding interactive effects between pollutants and climate change-related stressors is still scarce. Within this context, the present study aims to assess the differential ecotoxicological responses (antioxidant activity, heat shock response, protein degradation, endocrine disruption and neurotoxicity) of juvenile fish (Argyrosomus regius) tissues (muscle, gills, liver and brain) exposed to VFX (via water or feed), as well as to the interactive effects of warming (ΔT °C = +5 °C) and acidification (ΔpCO₂ ~ +1000 µatm, equivalent to ΔpH = -0.4 units), using an integrated multi-biomarker response (IBR) approach. Overall, results showed that VFX toxicity was strongly influenced by the uptake pathway, as well as by warming and acidification. More significant changes (e.g. increases surpassing 100% in lipid peroxidation, LPO, heat shock response protein content, HSP70/HSC70, and total ubiquitin content, Ub,) and higher IBR index values were observed when VFX exposure occurred via water (i.e. average IBR = 19, against 17 in VFX-feed treatment). The co-exposure to climate change-related stressors either enhanced (e.g. glutathione S-transferases activity (GST) in fish muscle was further increased by warming) or attenuated the changes elicited by VFX (e.g. vitellogenin, VTG, liver content increased with VFX feed exposure acting alone, but not when co-exposed with acidification). Yet, increased stress severity was observed when the three stressors acted simultaneously, particularly in fish exposed to VFX via water (i.e. average IBR = 21). Hence, the distinct fish tissues responses elicited by the different scenarios emphasized the relevance of performing multi-stressors ecotoxicological studies, as such approach enables a better estimation of the environmental hazards posed by pollutants in a changing ocean and, consequently, the development of strategies to mitigate them.

Bioaccumulation and ecotoxicological responses of juvenile white seabream (Diplodus sargus) exposed to triclosan, warming and acidification

Triclosan (TCS) is a synthetic microbial compound widely used in the formulation of various personal care products. Its frequent detection in marine ecosystems, along with its physical and chemical properties, suggest that TCS can be highly persistent, being easily bioaccumulated by biota and, therefore, eliciting various toxicological responses. Yet, TCS's mechanisms of bioaccumulation and toxicity still deserve further research, particularly focusing on the interactive effects with climate change-related stressors (e.g. warming and acidification), as both TCS chemical behaviour and marine species metabolism/physiology can be strongly influenced by the surrounding abiotic conditions. Hence, the aim of this study was to assess TCS bioaccumulation and ecotoxicological effects (i.e. animal fitness indexes, antioxidant activity, protein chaperoning and degradation, neurotoxicity and endocrine disruption) in three tissues (i.e. brain, liver and muscle) of juvenile Diplodus sargus exposed to the interactive effects of TCS dietary exposure (15.9 μg kg^-1 dw), seawater warming (ΔTºC = +5 °C) and acidification (ΔpCO₂ ∼ +1000 μatm, equivalent to ΔpH = -0.4 units). Muscle was the primary organ of TCS bioaccumulation, and climate change stressors, particularly warming, significantly reduced TCS bioaccumulation in all fish tissues. Furthermore, the negative ecotoxicological responses elicited by TCS were significantly altered by the co-exposure to acidification and/or warming, through either the enhancement (e.g. vitellogenin content) or counteraction/inhibition (e.g. heat shock proteins HSP70/HSC70 content) of molecular biomarker responses, with the combination of TCS plus acidification resulting in more severe alterations. Thus, the distinct patterns of TCS tissue bioaccumulation and ecotoxicological responses induced by the different scenarios emphasized the need to further understand the interactive effects between pollutants and abiotic conditions, as such knowledge enables a better estimation and mitigation of the toxicological impacts of climate change in marine ecosystems.

Bioenergetics-adverse outcome pathway: Linking organismal and suborganismal energetic endpoints to adverse outcomes

Adverse outcome pathways (AOPs) link toxicity across levels of biological organization, and thereby facilitate the development of suborganismal responses predictive of whole-organism toxicity and provide the mechanistic information necessary for science-based extrapolation to population-level effects. Thus far AOPs have characterized various acute and chronic toxicity pathways; however, the potential for AOPs to explicitly characterize indirect, energy-mediated effects from toxicants has yet to be fully explored. Indeed, although exposure to contaminants can alter an organism's energy budget, energetic endpoints are rarely incorporated into ecological risk assessment because there is not an integrative framework for linking energetic effects to organismal endpoints relevant to risk assessment (e.g., survival, reproduction, growth). In the present analysis, we developed a generalized bioenergetics-AOP in an effort to make better use of energetic endpoints in risk assessment, specifically exposure scenarios that generate an energetic burden to organisms. To evaluate empirical support for a bioenergetics-AOP, we analyzed published data for links between energetic endpoints across levels of biological organization. We found correlations between 1) cellular energy allocation and whole-animal growth, and 2) metabolic rate and scope for growth. Moreover, we reviewed literature linking energy availability to nontraditional toxicological endpoints (e.g., locomotor performance), and found evidence that toxicants impair aerobic performance and activity. We conclude by highlighting current knowledge gaps that should be addressed to develop specific bioenergetics-AOPs. Environ Toxicol Chem 2019;38:27-45. © 2018 SETAC.

Boric acid as a reference substance in avoidance behaviour tests with Porcellio dilatatus (Crustacea: Isopoda)

Isopods are macrodecomposers in terrestrial ecosystems, contributing to soil organic matter breakdown and nutrient cycling. They have been considered sensitive in laboratory tests designed to evaluate contaminants effects and are considered likely candidates to have a standardized protocol for ecotoxicity tests. For this purpose, a reference substance should be proposed as positive control in laboratory tests. This work aimed to evaluate the avoidance behaviour of the isopod species Porcellio dilatatus to boric acid (H₃BO₃; BA). Interlaboratory comparison tests were carried out based on the ISO guideline for earthworms, using tropical artificial soil as substrate, in the concentrations of 0, 125, 250, 500, 750, 1000, 1300 and 1800 mg BA kg^-1 soil. Avoidance behaviour was evaluated in group (six organisms per replicate) and in individual tests (one organism per replicate), in dual-section plastic boxes, which received control soil (not contaminated) in one side and tested soil (with BA) in another one. The percentage of organisms in each side was recorded after 48 h, and data were analysed using Fisher exact test (p < 0.05) and t-test. Results showed significant avoidance response in individual tests at 250 mg kg^-1 and in group tests at 500 mg kg^-1. Limited habitat function (< 20% of organisms) for both tests and laboratories were observed at the highest tested concentration of 1800 mg kg^-1, indicating the low sensitivity of this species to BA in avoidance tests, if compared to other substances in literature. Results showed that BA can be used as reference substance until a better option will be proposed.

Integrated multi-biomarker responses of juvenile seabass to diclofenac, warming and acidification co-exposure

Pharmaceutical drugs, such as diclofenac (DCF), are frequently detected in the marine environment, and recent evidence has pointed out their toxicity to non-target marine biota. Concomitantly, altered environmental conditions associated with climate change (e.g. warming and acidification) can also affect the physiology of marine organisms. Yet, the underlying interactions between these environmental stressors (pharmaceutical exposure and climate change-related stressors) still require a deeper understanding. Comprehending the influence of abiotic variables on chemical contaminants' toxicological attributes provides a broader view of the ecological consequences of climate change. Hence, the aim of this study was to assess the ecotoxicological responses of juvenile seabass Dicenthrachus labrax under the co-exposure to DCF (from dietary sources, 500 ± 36 ng kg^-1 dw), warming (ΔTºC = +5 °C) and acidification (ΔpCO₂ ∼1000 μatm, equivalent to ΔpH = -0.4 units), using an "Integrated Biomarker Response" (IBR) approach. Fish were exposed to these three stressors, acting alone or combined, for 28 days in a full cross-factorial design, and blood, brain, liver and muscle tissues were subsequently collected in order to evaluate: i) animal/organ fitness; ii) hematological parameters and iii) molecular biomarkers. Results not only confirmed the toxicological attributes of dietary exposure to DCF in marine fish species at the tissue (e.g. lower HSI), cellular (e.g. increased ENAs and lower erythrocytes viability) and molecular levels (e.g. increased oxidative stress, protein degradation, AChE activity and VTG synthesis), but also showed that such attributes are altered by warming and acidification. Hence, while acidification and/or warming enhanced some effects of DCF exposure (e.g. by further lowering erythrocyte viability, and increasing brain GST activity and Ub synthesis in muscle), the co-exposure to these abiotic stressors also resulted in a reversion/inhibition of some molecular responses (e.g. lower CAT and SOD inhibition and VTG synthesis). IBRs evidenced that an overall higher degree of stress (i.e. high IBR index) was associated with DCF and warming co-exposure, while the effects of acidification were less evident. The distinct responses observed when DCF acted alone or the animals were co-exposed to the drug together with warming and acidification not only highlighted the relevance of considering the interactions between multiple environmental stressors in ecotoxicological studies, but also suggested that the toxicity of pharmaceuticals can be aggravated by climate change-related stressors (particularly warming), thus, posing additional biological challenges to marine fish populations.

Seasonal changes in stress biomarkers of an exotic coastal species - Chaetopleura angulata (Polyplacophora) - Implications for biomonitoring

Knowledge on baseline values of stress biomarkers in natural conditions is urgent due to the need of reference values for monitoring purposes. Here we assessed the cellular stress response of the chiton Chaetopleura angulata in situ. Biomarkers commonly used in environmental monitoring (heat shock protein 70kDa, total ubiquitin, catalase, glutathione-S-transferase, superoxide-dismutase, lipid peroxidation) were analyzed in the digestive system, gills and muscle of C. angulata, under spring and summer conditions in order to assess seasonal tissue-specific responses. Season had an effect on all targeted organs, especially affecting the digestive system which displayed clear seasonal clusters. The respective Integrated Biomarker Response (IBR) showed a 7.2-fold seasonal difference. Muscle and gills showed similar IBRs between seasons making them appropriate organs to monitor chemical pollution as they were less responsive to seasonal variation. The most stable biomarkers in these organs were ubiquitin and superoxide-dismutase thus being reliable for monitoring purposes.

Metabolic responses of the isopod Porcellionides pruinosus to nickel exposure assessed by (1)H NMR metabolomics

This work aimed at characterizing the metabolome of the isopod Porcellionides pruinosus and at assessing its variations over 14 days under laboratory culture conditions and upon exposure to the contaminant metal Nickel (Ni). The spectral profiles obtained by (1)H NMR spectroscopy were thoroughly assigned and subjected to multivariate analysis in order to highlight consistent changes. Over 50 metabolites could be identified, providing considerable new knowledge on the metabolome of these model organisms. Several metabolites changed non-linearly with Ni dose and exposure time, showing distinct variation patterns for initial (4 days) and later time points (7 and 14 days). In particular, at day 4, several amino acids were increased and sugars were decreased (compared to controls), whereas these variations were inverted for longer exposure, possibly reflecting earlier and more intensive moulting. Other variations, namely in betaines and choline-containing compounds, were suggested to relate with osmoregulation and detoxification mechanisms. Ni also had a marked effect on several nucleotides (increased upon exposure) and a moderate impact on lipids (decreased upon exposure). Overall, this study has provided new information on the Ni-induced metabolic adaptations of the P. pruinosus isopod, paving the way for improved mechanistic understanding of how these model organisms handle soil contamination.

SIGNIFICANCE

This study provided, for the first time to our knowledge, a detailed picture of the NMR-detectable metabolome of terrestrial isopods and of its fluctuations in time and upon exposure to the contaminant metal Nickel. Several time- and dose-dependent changes were highlighted, providing mechanistic insight into how these important model organisms handle Ni contamination.