Biochemical characterization of cholinesterases in Enchytraeus albidus and assessment of in vivo and in vitro effects of different soil properties, copper and phenmedipham

Assessment of adverse effects of olive mill waste water and olive mill waste contaminated soil on springtail Folsomia candida

In recent years significant attention has been given to the problem of olive mill waste towards the environment. Still, there is a considerable gap in the knowledge of the impact of the olive mill wastewater (OMWW) and the olive mill waste contaminated soil (OMW CS) on non-target soil organisms. Springtails, as an important group of non-target soil organisms, are frequently used in ecotoxicological research. However, information on olive mill waste impact on the model species Folsomia candida is scarce. Therefore, in this study, we determined the effects of OMWW and OMW CS on survival, reproduction, neurotoxicity, oxidative stress, and available energy in springtail F. candida. The exposure to different ratios of OMWW and OMW CS showed higher toxicity of OMW CS in terms of survival (LC₅₀ = 32.34% of OMWW; LC₅₀ = 45.36% of OMW CS) and reproduction (EC₅₀ = 10.10% of OMWW; EC₅₀ = 19.44% of OMW CS). Furthermore, neurotoxicity (AChE induction), oxidative stress (SOD, GST, and MDA induction), and changes in available energy (decrease in lipid and carbohydrate content) have been observed. Those negative effects are likely consequences of the high phenol content specific to OMWW and OMW CS. Obtained results indicate that for the ecotoxicological assessment of various wastes it is essential to consider different tier level biomarkers to have a clear insight into the mechanism of action.

Annelid genomes: Enchytraeus crypticus, a soil model for the innate (and primed) immune system

Enchytraeids (Annelida) are soil invertebrates with worldwide distribution that have served as ecotoxicology models for over 20 years. We present the first high-quality reference genome of Enchytraeus crypticus, assembled from a combination of Pacific Bioscience single-molecule real-time and Illumina sequencing platforms as a 525.2 Mbp genome (910 gapless scaffolds and 18,452 genes). We highlight isopenicillin, acquired by horizontal gene transfer and conferring antibiotic function. Significant gene family expansions associated with regeneration (long interspersed nuclear elements), the innate immune system (tripartite motif-containing protein) and response to stress (cytochrome P450) were identified. The ACE (Angiotensin-converting enzyme) - a homolog of ACE2, which is involved in the coronavirus SARS-CoV-2 cell entry - is also present in E. crypticus. There is an obvious potential of using E. crypticus as a model to study interactions between regeneration, the innate immune system and aging-dependent decline.

Cholinesterases of marine fish: characterization and sensitivity towards specific chemicals

Inhibition of cholinesterases has been frequently used as a biomarker for contamination of aquatic environments, because these enzymes are frequent targets for toxic effects of contaminants, such as insecticides derived from phosphoric and carbamic acids. However, this enzyme is also responsive to other contaminants, including metals. The use of cholinesterase inhibition as effect criterion in ecotoxicology studies requires the previous characterization of the specific enzymatic forms that can be present in the different tissues and/or organs of species. This work characterized the soluble ChEs present in the brain and dorsal muscle of three marine fish species, namely Scomber scombrus, Sardina pilchardus and Chelidonichthys lucerna. Pesticides (chlorpyrifos) and metals (copper sulphate) in vitro assays were conducted to quantify the effects of these contaminants on cholinesterases activity. The results of this study showed that acetylcholinesterase (AChE) was the predominant form present in the brain tissues of the three species and in the muscle tissue of one species (Sardina pilchardus). For Scomber scombrus and Chelidonichthys lucerna, the cholinesterase form present in the muscle tissue evidenced properties between the classic acetylcholinesterase and those of pseudocholinesterase forms. The results for the metal (copper) and pesticide (chlorpyrifos) showed that this species may be suitable for monitoring contaminations for these types of contaminants.

Soluble esterases as biomarkers of neurotoxic compounds in the widespread serpulid Ficopomatus enigmaticus (Fauvel, 1923)

The characterization of soluble cholinesterases (ChEs) together with carboxylesterases (CEs) in Ficopomatus enigmaticus as suitable biomarkers of neurotoxicity was the main aim of this study. ChEs of F. enigmaticus were characterized considering enzymatic activity, substrate affinity (acetyl-, butyryl-, propionylthiocholine), kinetic parameters (K_m and V_max) and in vitro response to model inhibitors (eserine hemisulfate, iso-OMPA, BW284C51), and carbamates (carbofuran, methomyl, aldicarb, and carbaryl). CEs were characterized based on enzymatic activity, kinetic parameters and in vitro response to carbamates (carbofuran, methomyl, aldicarb, and carbaryl). Results showed that cholinesterases from F. enigmaticus showed a substrate preference for acetylthiocholine followed by propionylthiocholine; butyrylthioline was not hydrolyzed differently from other Annelida species. CE activity was in the same range of cholinesterase activity with acetylthiocholine as substrate; the enzyme activity showed high affinity for the substrate p-nytrophenyl butyrate. Carbamates inhibited ChE activity with propionylthiocholine as substrate to a higher extent than with acetylthiocoline. Also CE activity was inhibited by all tested carbamates except carbaryl. In vitro data highlighted the presence of active forms of ChEs and CEs in F. enigmaticus that could potentially be inhibited by pesticides at environmentally relevant concentration.

The sugarcane herbicide ametryn induces oxidative stress and developmental abnormalities in zebrafish embryos

Ametryn (AMT) is one of the most widely used herbicides in tropical sugarcane crops, the main culture of São Paulo State, Brazil. It is known as a diffuse pollutant, being found in surface water and sediment of water bodies adjacent to the crop fields. In the present study, the toxicity of AMT to zebrafish (Danio rerio) embryos was evaluated using developmental and biochemical endpoints. At the biochemical level, lactate dehydrogenase responded at the lowest concentration tested (4 μg L^-1) indicating a high demand of energy required to cope with the stress condition. Antioxidant enzyme levels were changed at intermediate/high concentrations while oxidative damage (lipid peroxidation) was observed at the last concentration tested (10 mg L^-1). This suggests that, like for other herbicides from the triazine group, oxidative stress is a major pathway of toxicity for AMT. Several developmental effects such as oedemas and tail deformities were also observed. The 96 h-EC₅₀ values calculated for different developmental parameters were between 17 and 29 mg L^-1. AMT also affected hatching (96 h-EC₅₀ = 22.5 mg L^-1) and positioning in the water column (96 h-EC₅₀ = 13.2 mg L^-1). In a previous work of the group, lethal toxicity of AMT showed to be much higher to adults than to embryos. However, in the present work, sublethal endpoints assessed suggest that important effects are observed at lower concentrations, improving the sensitivity of the embryo test. Moreover, in this work, sublethal effects were observed for concentrations in the same range as the ones found in the environment, and thus, given that this chemical is widely used in tropical fields, a refined evaluation of risk should be performed based on the monitoring of sublethal and long-term parameters and considering mixture scenarios.

Phytotoxicity of silver nanoparticles to Lemna minor: Surface coating and exposure period-related effects

Silver nanoparticles (Ag NPs) exponential production raises concern about their environmental impact. The effects of Ag NPs to aquatic plants remain scarcely studied, especially in extended exposures. This paper aims to evaluate Ag NPs effects in Lemna minor at individual and sub-individual levels, focusing on three variables: Ag form (NPs versus ions - Ag⁺), NPs surface coating (citrate vs polyvinylpyrrolidone - PVP) and exposure period (7 vs 14days). Endpoints were assessed at individual level (specific growth rate, chlorosis incidence and number of fronds per colony) and sub-individual level (enzymatic activities of catalase (CAT), guaiacol peroxidase (GPx) and glutathione-S-transferase (GST)). Generally, plants exposed to all Ag forms underwent decays on growth rate and fronds per colony, and increases on chlorosis, GPX and GST, but no effects on CAT. The most sensitive endpoints were specific growth rate and GPx activity, showing significant effects down to 0.05mg/L for Ag NPs and 3μg/L for Ag⁺, after 14days. Ag⁺ showed higher toxicity with a 14d-EC₅₀ of 0.0037mg Ag/L. Concerning surface coating, PVP-Ag NPs were more deleterious on growth rate and fronds per colony, whereas citrate-Ag NPs affected more the chlorosis incidence and GPx and GST activities. The exposure period significantly affected chlorosis: 14days triggered a chlorosis increase in Ag⁺-exposed plants and a decrease in Ag NPs-exposed plants when compared to 7days. Ag NPs induced an oxidative stress status in cells, thus ensuing upregulated enzymatic activity as a self-defense mechanism. Since Ag NPs dissolution might occur on a steady and continuous mode along time, and the average longevity of fronds, we propose longer exposures periods than the recommended by the OECD guideline. This approach would provide more relevant and holistic evidences on the overall response of freshwater plants to Ag NPs in an ecological relevant scenario.

Suitability of cholinesterase of polychaete Diopatra neapolitana as biomarker of exposure to pesticides: In vitro characterization

Cholinesterases of Diopatra neapolitana were characterized for their activity in whole body and different body segments (apical, intermediate, posterior), substrate affinity (acetyl-, butyryl-, propionylthiocholine), kinetic parameters (K_m and V_max) and in vitro response to model inhibitors (eserine hemisulfate, isoOMPA, BW284C51) and carbamates (carbofuran, methomyl, aldicarb and carbaryl). Results showed that the rate of hydrolysis for acetyl- and propionylthiocholine was higher in the posterior segment than the apical/intermediate segments and whole body. Cholinesterases of D. neapolitana showed a substrate preference for acetylthiocholine followed by propionylthiocholine; butyrylthioline was poorly hydrolyzed indicating, together with the absence of inhibition by the specific inhibitor and the absence of reactive bands in native electrophoresis, a lack of an active butyrylcholinesterase, differently than that observed in other Annelida species. The degree of inhibition by selected carbamates of cholinesterase activity with propionylthiocholine as substrate was higher than that observed with ATChI-ChE activity; aldicarb showed the highest inhibitory effect.

Brain acetylcholinesterase of jaguar cichlid (Parachromis managuensis): From physicochemical and kinetic properties to its potential as biomarker of pesticides and metal ions

This contribution aimed to characterize physicochemical and kinetic parameters of the brain cholinesterases (ChEs) from Parachromis managuensis and investigate the in vitro effects of pesticides and metal ions on its activity intending to propose as biomarker. This species is suitable for this investigation because (1) it was recently introduced in Brazil becoming invasive (no restrictions on capture) and (2) occupies the top of the food chain (being subject to bioaccumulation). The enzyme extract was exposed to 10 metal ions (Al(3+), Ba(2+), Cd(2+), Cu(2+), Hg(2+), Mg(2+), Mn(2+), Pb(2+), Fe(2+) and Zn(2+)) and ChEs selective inhibitors (BW284c51, Iso-OMPA, neostigmine and serine). The extract was also incubated with organophosphate (dichlorvos) and carbamate pesticides (carbaryl and carbofuran). Inhibition parameters (IC20, IC50 and ki) were determined. Selective inhibitors and kinetic parameters confirmed acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) -like as responsible for the ChE activities, most AChE. The IC50 values for pesticides were: 1.68μM (dichlorvos); 4.35μM (carbaryl) and 0.28μM (carbofuran). Most of the analyzed ions did not show significant effect at 1mM (p=0.05), whereas the following ions inhibited the enzyme activity in the order: Hg(2+)>Cu(2+)>Cd(2+)>Zn(2+). Mercury ion strongly inhibited the enzyme activity (IC20=0.7μM). The results about allow to conclude that P. managuensis brain AChE is a potential biomarker for heavy metals and pesticides under study, mainly for the carbamate carbofuran once it was capable to detect 6-fold lower levels than the limit concentration internationally recommended.

Effects of short-term exposure to fluoxetine and carbamazepine to the collembolan Folsomia candida

Pharmaceuticals, emerging environmental contaminants, have their ecotoxicological effects to non-target organisms in soil largely unknown. This study assessed short-term effects of two human pharmaceuticals, carbamazepine and fluoxetine, to Folsomia candida. Avoidance to spiked soils was assessed after 48 and 96 h exposure and biochemical changes (acetylcholinesterase and glutathione S-transferase activities, and lipid peroxidation levels) after 96 h. F. candida avoided soils spiked with 0.04, 0.4 and 4 mg carbamazepine kg(-1) after 48 h. However, higher number of organisms were found in soils with 40 mg carbamazepine kg(-1), a behavior also displayed for 40 mg fluoxetine kg(-1) spiked soils. After 96 h, F. candida showed avoidance behavior to soils with 4 and 40 mg carbamazepine kg(-1). Acetylcholinesterase activity decreased in 0.4 mg fluoxetine kg(-1) exposed organisms. Peroxidative damages were detected in organisms exposed to 4 and 40 mg kg(-1) carbamazepine and glutathione S-transferase inhibition was observed at 40 mg kg(-1). Data suggests that carbamazepine and fluoxetine may pose risk to soil collembolan.

Sensitivity of the sea snail Gibbula umbilicalis to mercury exposure--linking endpoints from different biological organization levels

Mercury contamination is a common phenomenon in the marine environment and for this reason it is important to develop cost-effective and relevant tools to assess its toxic effects on a number of different species. To evaluate the possible effects of Hg in the sea snail Gibbula umbilicalis, animals were exposed to increasing concentrations of the contaminant in the ionic form for 96 h. After this exposure period, mortality, feeding and flipping behavior, the activity of the biomarkers glutathione S-transferase, superoxide dismutase, catalase, lactate dehydrogenase and cholinesterase, the levels of lipid peroxidation and cellular energy allocation were measured. After 96 h of exposure to the highest Hg concentration (≈LC20), there was a significant inhibition of the cholinesterase activity as well as impairment in the flipping behavior and post-exposure feeding of the snails. Cholinesterase inhibition was correlated with the impairment of behavioral responses also caused by exposure to Hg. These endpoints, including the novel flipping test, revealed sensitivity to Hg and might be used as relevant early warning indicators of prospective effects at higher biological organization levels, making these parameters potential tools for environmental risk assessment. The proposed test species showed sensitivity to Hg and proved to be a suitable and resourceful species to be used in ecotoxicological testing to assess effects of other contaminants in marine ecosystems.

Antioxidant and neurotoxicity markers in the model organism Enchytraeus albidus (Oligochaeta): mechanisms of response to atrazine, dimethoate and carbendazim

The present study aimed to investigate the effects of dimethoate, atrazine and carbendazim on the antioxidant defences and neuronal function of the soil organism Enchytraeus albidus. Effects were studied at concentrations known to affect their reproduction (EC20, EC50 and EC90) and along time (2, 4, 8, 14 and 21 days). In general, responses were more pronounced at periods of exposure longer than 8 days and at the highest concentrations. Multivariate statistics (RDA-PRC) clearly displayed that exposure duration had an effect itself, biomarkers' responses showed interaction for all pesticides and catalase scored consistently high, indicating its relevancy in the group of measured markers. Univariate analysis indicated oxidative stress for all pesticides and atrazine induced oxidative damage in lipids. Atrazine seems to be effectively metabolized by GST of the biotransformation system, as its activity significantly increased after exposure to this pesticide. Dimethoate caused ChE inhibition, indicating an impairment of the neuronal function. Carbendazim impaired the antioxidant system, but no oxidative damage was observed, along with any effects on the ChE activity. The integrated biomarker response analysis was performed but we suggest modifications due to limiting artefacts.

The use of cholinesterase as potential biomarker: In vitro characterization in the polychaete Capitella teleta

The ecological relevance of polychaetes coupled with their easy culture and maintenance in the laboratory, has led them to become increasingly used in marine ecotoxicological studies, raising the need to validate frequently applied monitoring tools at various biological levels. The present study was aimed to characterize the cholinesterases (ChE) activity in the polychaete Capitella teleta, using three substrates (acetylthiocholine iodide, propionylthiocholine iodide, and S-butyrylthiocholine iodide) and four known inhibitors (eserine hemisulfate, BW284c51, iso-OMPA and chlorpyrifos-oxon). Results showed that most of the measured cholinesterase activity was acetylcholinesterase (AChE). Inhibition of enzyme kinetic experiments denoted that sensitivity of C. teleta's ChE to the organophosphorous metabolite chlorpyrifos-oxon (IC₅₀=60.72 nM) was analogous to some fish species. This study highlights the relevance of ChE characterization before its use as a biomarker in ecotoxicology and biomonitoring studies.

Cholinesterase activity in the caddisfly Sericostoma vittatum: Biochemical enzyme characterization and in vitro effects of insecticides and psychiatric drugs

Sericostoma vittatum is a caddisfly species, endemic to the Iberian Peninsula, proposed as a biomonitor species for lotic ecosystems. Since inhibition of cholinesterases׳ (ChE) activity has been used to evaluate the exposure of macroinvertebrates to organophosphates and carbamate pesticides, this work intended to characterize the ChE present in this species so their activity can be used as a potential biomarker of exposure. Biochemical and pharmacological properties of ChE were characterized in this caddisfly species using different substrates (acetylthiocholine iodide, propionylthiocholine iodide, and butyrylthiocholine iodide) and selective inhibitors (eserine sulfate, BW284c51, and iso-OMPA). Also, the in vitro effects of two insecticides (carbaryl and chlorantraniliprole) and two psychiatric drugs (fluoxetine and carbamazepine) on ChE activity were investigated. The results suggest that S. vittatum possess mainly AChE able to hydrolyze both substrates acetylthiocholine and propionylthiocholine since: (1) it hydrolyzes the substrate acetylthiocholine and propionylcholine at similar rates and butyrylthiocholine at a much lower rate; (2) it is highly sensitive to eserine sulfate and BW284c51, but not to iso-OMPA; and (3) its activity is inhibited by excess of substrate, a characteristic of typical AChE. in vitro inhibitions were observed only for carbaryl exposure while exposure to chlorantraniliprole and to relevant environmental concentrations of psychiatric drugs did not cause any significant effect on AChE activity. This study suggests that AChE activity in caddisflies can indeed be used to discriminate the effects of specific insecticides in monitoring programs. The use of non-target species such as caddisflies in ecotoxicological research in lotic ecosystems is also discussed.

Effects of environmentally relevant concentrations of metallic compounds on the flatfish Scophthalmus maximus: biomarkers of neurotoxicity, oxidative stress and metabolism

Flatfish species, such as the turbot (Scophthalmus maximus), are common targets for toxic effects, since they are exposed through the food chain (ingestion of contaminated preys) and are in direct contact with the waterborne contaminant and sediments. Furthermore, these fish species live in close proximity to interstitial water that frequently dissolves high amounts of contaminants, including metals. Despite this significant set of characteristics, the present knowledge concerning flatfish contamination and toxicity by metals is still scarce. To attain the objective of assessing the effects of metals on a flatfish species, S. maximus specimens were chronically exposed to lead, copper and zinc, at ecologically relevant concentrations, and biochemical (oxidative stress: catalase and glutathione S-transferases activities, and lipid peroxidation; neurotoxicity: cholinesterase activity) parameters were assessed on selected tissues (gills and liver). Copper had no significant effects on all tested parameters; lead was causative of significant increases in liver GSTs activities and also in lipoperoxidation of gill tissue; exposure to zinc caused a significant increase in catalase activity of gill tissue. None of the tested metals elicited noteworthy effects in terms of neurotoxicity. The obtained results showed that only the metal lead is of some environmental importance, since it was able to cause deleterious modifications of oxidative nature at relevant concentrations.

Risk assessment of petroleum-contaminated soil using soil enzyme activities and genotoxicity to Vicia faba

Pollution caused by petroleum is one of the most serious problems worldwide. To better understand the toxic effects of petroleum-contaminated soil on the microflora and phytocommunity, we conducted a comprehensive field study on toxic effects of petroleum contaminated soil collected from the city of Daqing, an oil producing region of China. Urease, protease, invertase, and dehydrogenase activity were significantly reduced in microflora exposed to contaminated soils compared to the controls, whereas polyphenol oxidase activity was significantly increased (P < 0.05). Soil pH, electrical conductivity, and organic matter content were correlated with total petroleum hydrocarbons (TPHs) and a correlation (P < 0.01) existed between the C/N ratio and TPHs. Protease, invertase and catalase were correlated with TPHs. The Vicia faba micronucleus (MN) test, chromosome aberrant (CA) analyses, and the mitotic index (MI) were used to detect genotoxicity of water extracts of the soil. Petroleum-contaminated samples indicated serious genotoxicity to plants, including decreased index level of MI, increased frequency of MN and CA. The combination of enzyme activities and genotoxicity test via Vicia faba can be used as an important indicator for assessing the impact of TPH on soil ecosystem.

Effects of temperature and copper pollution on soil community--extreme temperature events can lead to community extinction

Global warming affects ecosystems and species' diversity. The physiology of individual species is highly influenced by changes in temperature. The effects on species communities are less studied; they are virtually unknown when combining effects of pollution and temperature. To assess the effects of temperature and pollution in the soil community, a 2-factorial soil mesocosms multispecies experiment was performed. Three exposure periods (28 d, 61 d, and 84 d) and 4 temperatures (19 °C, 23 °C, 26 °C, and 29 °C) were tested, resembling the mean annual values for southern Europe countries and extreme events. The soil used was from a field site, clean, or spiked with Cu (100 mg Cu/kg). Results showed clear differences between 29 °C treatment and all other temperature treatments, with a decrease in overall abundance of organisms, further potentiated by the increase in exposure time. Folsomia candida was the most abundant species and Enchytraeus crypticus was the most sensitive to Cu toxicity. Differences in species optimum temperatures were adequately covered: 19 °C for Hypoaspis aculeifer or 26 °C for E. crypticus. The temperature effects were more pronounced the longer the exposure time. Feeding activity decreased with higher temperature and exposure time, following the decrease in invertebrate abundance, whereas for the same conditions the organic matter turnover increased. Hence, negative impacts on ecosystem services because of temperature increase can be expected by changes on soil function and as consequence of biodiversity loss.

Effects of oxytetracycline and amoxicillin on development and biomarkers activities of zebrafish (Danio rerio)

Antibiotics have been widely used in human and veterinary medicine to treat or prevent diseases. Residues of antibiotics have been found in aquatic environments, but their effects on fish have been not properly investigated. This work aimed to assess the sub-lethal effects of oxytetracycline and amoxicillin on zebrafish development and biomarkers. Embryos and adults were exposed during 96 h to amoxicillin and oxytetracycline following OECD guidelines. Tissues of adults and pools of embryos were used for catalase, glutathione-S-transferases and lactate dehydrogenase determinations. Amoxicillin caused premature hatching (48 h-EC50=132.4 mg/l) whereas oxytetracycline cause delayed hatching of embryos (72 h-EC50=127.6 mg/l). Moreover, both antibiotics inhibited catalase and induced glutathione-S-transferases in zebrafish adults. However, only oxytetracycline induced lactate dehydrogenase. Short-term effects of antibiotics were observed at high doses (mg/l) indicating that physiological impairment in fish populations is unlike to occur. However, effects of chronic exposures to low doses of ABs must be investigated.

Lethal and sub lethal effects of the biocide chlorhexidine on aquatic organisms

Chlorhexidine is among the most used biocides in Europe, however its toxicity to aquatic organisms is scarcely known. The main objective of this study was to assess the lethal and sub lethal effects of chlorhexidine digluconate (ChD) on four aquatic model organisms: the bacteria Vibrio fischeri, the algae Pseudokirchneriella subcapitata, the crustacean Daphnia magna and the embryos of the fish Danio rerio. ChD was very toxic to algae and crustaceans, with a 72 h-EC50 of 62.2 μg/l and a 48 h-EC50 of 45.0 μg/l, respectively. Toxicity to fish embryos and the bacteria was lower, with a 96 h-EC50 of 804.0 μg/l and a 15 min-EC50 of 1,694.0 μg/l, respectively. Concerning sub lethal effects on D. magna (feeding inhibition) a 6 h-EC50 of 503.7 μg/l was obtained. In fish, ChD caused developmental abnormalities, namely alterations in the amniotic fluid (48 h-EC20 of 753.6 μg/l) and early hatching. Moreover, enzymatic biomarkers on fish embryos showed an induction of cholinesterase activity in all ChD tested concentrations (80-900 μg/l). The catalase activity was also induced at the highest concentration tested (900 μg/l) whereas no changes were observed for glutathione-S-transferase and lactate dehydrogenase activities. The toxicity of ChD to the algae and crustacean raises concerns about its potential effects in aquatic food webs, since these organisms are in the base of trophic chains, and highlights the need for further studies on ChD toxicity to aquatic organisms.

Dimethoate affects cholinesterases in Folsomia candida and their locomotion--false negative results of an avoidance behaviour test

The main mode of action of organophosphate insecticides is to inhibit acetylcholinesterase (AChE), which causes neuromuscular paralysis leading ultimately to death. The collembolan Folsomia candida is an important and standard test species in ecotoxicology, where effects on avoidance behaviour are assessed. Being related to insects they represent potential targets of insecticides such as the organophosphate dimethoate. In the present study we exposed F. candida to dimethoate having 2 main aims: 1) to assess the ability of F. candida to avoid it, and 2) to assess its effect on the cholinergic synapses to explore the link. For the latter, several sub-steps were needed: a) to characterise the existing ChE types and b) assess ChE activity (via exposure in vitro and in vivo). No avoidance was observed within the tested concentration range (0-0.32-1-3.2-10-32 mg/kg), in fact an apparent "attraction" (more animals on the spiked side) was observed. As expected, there was a significant decrease of AChE activities (AChE being the main ChE type) with an increase of dimethoate dose (IC(50)=1.4 mg/kg). Further, post-exposure video records showed that organisms were still alive in the spiked soil but lacked the locomotion ability (immobilised). The AChE inhibition correlated positively with immobilisation. Hence, this observation also showed that the apparent "attraction" behaviour observed in the avoidance test is rather a direct effect of not being able to escape due to paralysis hence a false-negative avoidance. This can constitute a confounding factor in an avoidance behaviour test and consequent interpretation, which is not accounted for at present.

Differential gene expression analysis in Enchytraeus albidus exposed to natural and chemical stressors at different exposure periods

The soil oligochaete Enchytraeus albidus is a standard test organism used in biological testing for Environmental Risk Assessment (ERA). Although effects are known at acute and chronic level through survival, reproduction and avoidance behaviour endpoints, very little is known at the sub-cellular and molecular levels. In this study, the effects of soil properties (clay, organic matter and pH) and of the chemicals copper and phenmedipham were studied on E. albidus gene expression, during exposure periods of 2, 4 and 21 days, using DNA microarrays based on a normalised cDNA library for this test species (Amorim et al. 2011). The main objectives of this study were: (1) to assess changes in gene expression of E. albidus over time, and (2) to identify molecular markers for natural and chemical exposures. Results showed an influence of exposure time on gene expression. Transcriptional responses to phenmedipham were seen at 2 days while the responses to copper and the different soils were more pronounced at 4 days of exposure. Some genes were differentially expressed in a stress specific manner and, in general, the responses were related with effects in the energy metabolism and cell growth.

Reproduction and biochemical responses in Enchytraeus albidus (Oligochaeta) to zinc or cadmium exposures

To better understand chemical modes of action, emphasis has been given to stress responses at lower levels of biological organization. Cholinesterases and antioxidant defenses are among the most used biomarkers due to their crucial role in the neurocholinergic transmission and in cell homeostasis preventing DNA damage, enzymatic inactivation and lipid peroxidation. The main goal of this study was to investigate the effects of zinc and cadmium on survival and reproduction of E. albidus and to assess metals oxidative stress potential and neurotoxic effects at concentrations that affected reproduction. Both metals affected the enchytraeids' survival and reproduction and induced significant changes in the antioxidant defenses as well as increased lipid peroxidation, indicating oxidative damage. This study demonstrates that determining effects at different levels of biological organization can give better information on the physiological responses of enchytraeids in metal contamination events and further unravel the mechanistic processes dealing with metal stress.

Effect of Cu-nanoparticles versus one Cu-salt: analysis of stress biomarkers response in Enchytraeus albidus (Oligochaeta)

In the present study, the main goal was to compare the effects of ionic copper versus copper nanoparticles in Enchytraeus albidus assessing the effect at the biomarker level, testing different concentrations and exposure times. Measured parameters were lipid peroxidation (LPO), total, reduced and oxidized glutathione content (TG, GSH and GSSG), the enzymatic activity of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx), glutathione S-transferases (GSTs) and cholinesterases (ChEs). Results showed that both salt- and nano-copper caused oxidative stress and damage to E. albidus, as confirmed by LPO levels, and effects could be discriminated between the copper forms. Nevertheless and despite the visible discrimination between nano and the salt form (time and exposure dependent), there was no single or a set of biomarkers that provided the best discrimination.