Transgenerational Effects of Toxicants: An Extension of the Daphnia 21-day Chronic Assay?

History of exposure to copper influences transgenerational gene expression responses in Daphnia magna

The establishment of transgenerational effects following chemical exposure is a powerful phenomenon, capable of modulating ecosystem health beyond exposure periods. This study assessed the transgenerational effects occurring due to copper exposure in the invertebrate D. magna at the transcriptional level, while evaluating the role of exposure history on such responses. Thus, daphnids acclimated for several generations in a copper vs. clean medium were then exposed for one generation (F0) to this metal, and monitored for the following non-exposed generations (F1, F2 and F3). Organisms differing in exposure histories showed remarkably different transcriptional profiles at the F0, with naïve organisms being more profoundly affected. These trends were confirmed for F3 treatments, which presented different transcriptional patterns for genes involved in detoxification, oxidative stress, DNA damage repair, circadian clock functioning and epigenetic regulation. Furthermore, regardless of exposure history, a great number of histone modifier genes were always found transcriptionally altered, thus suggesting the involvement of histone modifications in the response of Daphnia to metal exposure. Lastly, remarkably distinct transgenerational transcriptional responses were found between naïve and non-naïve organisms, thereby highlighting the influence of exposure history on gene expression and confirming the capacity of metals to determine transgenerational transcriptional effects across non-exposed generations.

Toxicity of butylone and its enantiomers to Daphnia magna and its degradation/toxicity potential using advanced oxidation technologies

Butylone (BTL) is a chiral synthetic cathinone available as a racemate and reported as contaminant in wastewater effluents. However, there are no studies on its impact on ecosystems and possible enantioselectivity in ecotoxicity. This work aimed to evaluate: (i) the possible ecotoxicity of BTL as racemate or its isolated (R)- and (S)- enantiomers using Daphnia magna; and (ii) the efficiency of advanced oxidation technologies (AOTs) in the removal of BTL and reduction of toxic effects caused by wastewaters. Enantiomers of BTL were obtained by liquid chromatography (LC) using a chiral semi-preparative column. Enantiomeric purity of each enantiomer was > 97 %. For toxicity assessment, a 9-day sub-chronic assay was performed with the racemate (at 0.10, 1.0 or 10 μg L-1) or each enantiomer (at 0.10 or 1.0 μg L-1). Changes in morphophysiological, behavioural, biochemical and reproductive endpoints were observed, which were dependent on the form of the substance and life stage of the organism (juvenile or adult). Removal rates of BTL in spiked wastewater (10 μg L-1) treated with different AOTs (ultraviolet, UV; ozonation, O3; and UV/O3) were similar and lower than 29 %. The 48 h D. magna acute toxicity assays demonstrated a reduction in the toxicity of the treated spiked effluents, but no differences were found amongst AOTs treatments. These results warn for the contamination and negative impact of BTL on ecosystems and highlight the need for efficient removal processes.

Aging of nanosized titanium dioxide modulates the effects of dietary copper exposure on Daphnia magna - an assessment over two generations

Nanosized titanium dioxide (nTiO2) is widely used in products, warranting its discharge from various sources into surface water bodies. However, nTiO2 co-occurs in surface waters with other contaminants, such as metals. Studies with nTiO2 and metals have indicated that the presence of natural organic matter (NOM) can mitigate their toxicity to aquatic organisms. In addition, "aging" of nTiO2 can affect toxicity. However, it is a research challenge, particularly when addressing sublethal responses from dietary exposure over multiple generations. We, therefore exposed the alga Desmodesmus subspicatus to nTiO2 (at concentrations of 0.0, 0.6 and 3.0 mg nTiO2/L) in nutrient medium aged for 0 or 3 days with copper (Cu) at concentrations of 0 and 116 µg Cu/L and with NOM at concentrations equivalent to 0 and 8 mg total organic carbon (TOC) per litre. Subsequently, the exposed alga was fed to Daphnia magna for 23 days over two generations and survival, reproduction and body length were assessed as endpoints of toxicity. In parallel, Cu accumulation and depuration from D. magna were measured. The results indicate that the reproduction of D. magna was the most sensitive parameter in this study, being reduced by 30% (at both parental (F0) and filial (F1) generations) and 50% (at F0 but not F1) due to the dietary Cu exposure in combination with nTiO2 for 0 and 3 days aging, respectively. There was no relationship between the effects observed on reproduction and Cu body burden in D. magna. Moreover, D. magna from the F1 generation showed an adaptive response to Cu in the treatment with 3.0 mg nTiO2/L aged for 3 days, potentially due to epigenetic inheritance. Unexpectedly, the presence of NOM hardly changed the observed effects, pointing towards the function of algal exopolymeric substances or intracellular organic matter, rendering the NOM irrelevant. Ultimately, the results indicate that the transferability of the impacts observed during the F0 to the responses in the F1 generation is challenging due to opposite effect directions. Additional mechanistic studies are needed to unravel this inconsistency in the responses between generations and to support the development of reliable effect models.

Ecotoxicological Effects of Potassium Dichromate on the Tadpole Shrimp Triops longicaudatus

The tadpole shrimp Triops longicaudatus is a freshwater crustacean with fast embryonic and larval development, short life cycle, and high fecundity. They are very active swimmers of a reasonable size, easy to spot and record. Such characteristics make it a promising candidate as an experimental model in ecotoxicology to evaluate the effects of aquatic pollutants, particularly using its locomotor behavior as an endpoint. To evaluate the sensitivity of T. longicaudatus and develop endpoints of interest, we conducted exposure experiments with lethal and sub-lethal concentrations of potassium dichromate, a compound known for its ecotoxicological importance and as a hexavalent chromium source. The endpoints evaluated were mortality, growth, sexual maturation, reproductive output, cholinesterase activity and locomotor/swimming behavior. The 96 h median lethal concentration was found to be 65 µg/L. Furthermore, exposure to potassium dichromate at higher concentrations had a significant negative impact on the growth rate of T. longicaudatus in terms of both body mass and length. The time for maturation was also delayed at higher concentrations. In addition, locomotor behavior allowed for the discrimination of all tested chromium concentrations and the control group and from each other, proving to be the most sensitive endpoint. Overall, the data support the potential of T. longicaudatus as a model for ecotoxicity testing, using apical endpoints with impact at the population level; in particular, results suggest that behavior assessments in this species might be useful for detecting hazardous compounds in environmental monitoring of freshwater ecosystems.

Long-term toxicity of chlorpromazine, diclofenac and two lanthanides on three generations of Ceriodaphnia dubia

Amultigenerational study on Ceriodaphnia dubia was carried out by exposing three subsequent generations to pharmaceuticals chlorpromazine (CPZ) and diclofenac (DCF), and two lanthanide chlorides, gadolinium as GdCl3 and europium as EuCl3. As the treatments, environmentally relevant concentrations were chosen (0.001, 0.01 and 0.1 mg/L for CPZ; 0.1, 1 and 10 mg/L for DCF; 0.425, 4.25 and 42.5 µg/L for Gd and 0.41, 4.1 and 41 µg/L for Eu). Survival, population growth and reproduction success were evaluated at 21 and 30 days of exposure, and the whole observation period lasted 40 days. The least sensitive to all selected substances was the first daphnid generation (F1). Within 21-day exposure, no significant effects of the psychotropic drug CPZ on C. dubia survival were observed in generations F1-F3. The anti-inflammatory drug DCF did not affect survival in the F1 generation; however, it significantly reduced survival in the F3 generation at 1-10 mg/L. Both lanthanides did not affect survival in the F1 and F2 generations of C. dubia but considerably decreased survival in the F3 at 4-42 µg/L. Both pharmaceuticals stimulated the reproduction of C. dubia in the F1 generation, while inhibition occurred at the highest tested concentrations in generations F2 and F3. The inhibitory effect on the reproductive success of lanthanides in the F2 generation resembled that for CPZ but not for DCF. The dynamics of adverse effects during the 21-30-day period revealed that despite increased mortality in the controls (up to 30%), concentrations used in the study minified, in most instances, the survival and aggravated population growth and reproduction success of C. dubia. Our data suggest that C. dubia as a test organism can be used for 21 days in multigenerational investigations, especially when testing close to environmental concentrations. In this respect, the standard C. dubia chronic toxicity assay seems limited since prolonged observations and several generations of daphnids are required to obtain reliable information for the risk assessment of potentially aggressive chemicals.

The complexity of micro- and nanoplastic research in the genus Daphnia - A systematic review of study variability and a meta-analysis of immobilization rates

In recent years, the number of publications on nano- and microplastic particles (NMPs) effects on freshwater organisms has increased rapidly. Freshwater crustaceans of the genus Daphnia are widely used in ecotoxicological research as model organisms for assessing the impact of NMPs. However, the diversity of experimental designs in these studies makes conclusions about the general impact of NMPs on Daphnia challenging. To approach this, we systematically reviewed the literature on NMP effects on Daphnia and summarized the diversity of test organisms, experimental conditions, NMP properties and measured endpoints to identify gaps in our knowledge of NMP effects on Daphnia. We use a meta-analysis on mortality and immobilization rates extracted from the compiled literature to illustrate how NMP properties, study parameters and the biology of Daphnia can impact outcomes in toxicity bioassays. In addition, we investigate the extent to which the available data can be used to predict the toxicity of untested NMPs based on the extracted parameters. Based on our results, we argue that focusing on a more diverse set of NMP properties combined with a more detailed characterization of the particles in future studies will help to fill current research gaps, improve predictive models and allow the identification of NMP properties linked to toxicity.

The occurrence of emerging compounds in real urban wastewater before and after the COVID-19 pandemic in Cali, Colombia

The COVID-19 pandemic is considered one of the most significant global disasters in the last years. The rapid increase in infections, deaths, treatment, and the vaccination process has resulted in the excessive use of pharmaceuticals that have entered the environment as micropollutants. Considering the prior information about the presence of pharmaceuticals found in the wastewater of Cali, Colombia, which was collected from 2015 to 2022. The data monitored after the COVID-19 pandemic showed an increase in the concentration of analgesics and anti-inflammatory drugs of up to 91%. This increase was associated with the consumption of pharmaceuticals for mild symptoms, such as fever and pain. Moreover, the increase in concentration of pharmaceuticals poses a highly ecological threat, which was up to 14 times higher than that reported before of COVID-19 pandemic. These results showed that the COVID-19 had not only impacted human health but also had an effect on environmental health.

Combined exposure of polystyrene microplastics and carbamazepine induced transgenerational effects on the reproduction of Daphnia magna

Polystyrene microplastics (PS MPs) and carbamazepine (CBZ) are frequently detected in freshwater ecosystems. However, the transgenerational effects of PS MPs and CBZ on the reproduction of aquatic organisms and the corresponding mechanisms are still unclear. In the present study, Daphnia magna was used to evaluate the reproductive toxicity in two consecutive generations (F0, F1). The molting and reproduction parameters, the expression of reproduction, and the toxic metabolism genes were examined after 21-day exposure. A significantly enhanced toxicity was observed in the presence of 5 μm PS MPs and CBZ. Chronic exposure results showed that the 5 μm PS MPs alone, CBZ alone, and their mixtures exerted significant reproductive toxicity of D. magna. The results of RT-qPCR showed transcripts of genes related to reproduction (cyp314, ecr-b, cut, vtg1, vtg2, dmrt93b) and toxic metabolism (cyp4, gst) were altered in both the F0 and F1. In addition, for the F0, gene transcriptional changes of reproduction were not fully translated into physiological performance, probably due to the compensatory responses caused by the low dose of PS MPs alone, CBZ alone, and their mixtures. Whereas for the F1, the trade-off between reproduction and toxic metabolism at gene levels was observed, which translated into a significant reduction in the total neonate number of F1. These findings suggest that long-term exposure to MPs and CBZ can cause serious reproduction damage to aquatic animals, which needs to be given sufficient attention.

Freshwater crustacean exposed to active pharmaceutical ingredients: ecotoxicological effects and mechanisms

Concerns over the ecotoxicological effects of active pharmaceutical ingredients (APIs) on aquatic invertebrates have been raised in the last decade. While numerous studies have reported the toxicity of APIs in invertebrates, no attempt has been made to synthesize and interpret this dataset in terms of different exposure scenarios (acute, chronic, multigenerational), multiple crustacean species, and the toxic mechanisms. In this study, a thorough literature review was performed to summarize the ecotoxicological data of APIs tested on a range of invertebrates. Therapeutic classes including antidepressants, anti-infectives, antineoplastic agents, hormonal contraceptives, immunosuppressants, and neuro-active drugs exhibited higher toxicity to crustaceans than other API groups. The species sensitivity towards APIs exposure is compared in D. magna and other crustacean species. In the case of acute and chronic bioassays, ecotoxicological studies mainly focus on the apical endpoints including growth and reproduction, whereas sex ratio and molting frequency are commonly used for evaluating the substances with endocrine-disrupting properties. The multigenerational and "Omics" studies, primarily transcriptomics and metabolomics, were confined to a few API groups including beta-blocking agents, blood lipid-lowing agents, neuroactive agents, anticancer drugs, and synthetic hormones. We emphasize that in-depth studies on the multigenerational effects and the toxic mechanisms of APIs on the endocrine systems of freshwater crustacean are warranted.

Integrated Approach for Synthetic Cathinone Drug Prioritization and Risk Assessment: In Silico Approach and Sub-Chronic Studies in Daphnia magna and Tetrahymena thermophila

Synthetic cathinones (SC) are drugs of abuse that have been reported in wastewaters and rivers raising concern about potential hazards to non-target organisms. In this work, 44 SC were selected for in silico studies, and a group of five emerging SC was prioritized for further in vivo ecotoxicity studies: buphedrone (BPD), 3,4-dimethylmethcathinone (3,4-DMMC), butylone (BTL), 3-methylmethcathinone (3-MMC), and 3,4-methylenedioxypyrovalerone (MDPV). In vivo short-term exposures were performed with the protozoan Tetrahymena thermophila (28 h growth inhibition assay) and the microcrustacean Daphnia magna by checking different indicators of toxicity across life stage (8 days sublethal assay at 10.00 µg L^-1). The in silico approaches predicted a higher toxic potential of MDPV and lower toxicity of BTL to the model organisms (green algae, protozoan, daphnia, and fish), regarding the selected SC for the in vivo experiments. The in vivo assays showed protozoan growth inhibition with MDPV > BPD > 3,4-DMMC, whereas no effects were observed for BTL and stimulation of growth was observed for 3-MMC. For daphnia, the responses were dependent on the substance and life stage. Briefly, all five SC interfered with the morphophysiological parameters of juveniles and/or adults. Changes in swimming behavior were observed for BPD and 3,4-DMMC, and reproductive parameters were affected by MDPV. Oxidative stress and changes in enzymatic activities were noted except for 3-MMC. Overall, the in silico data agreed with the in vivo protozoan experiments except for 3-MMC, whereas daphnia in vivo experiments showed that at sublethal concentrations, all selected SC interfered with different endpoints. This study shows the importance to assess SC ecotoxicity as it can distress aquatic species and interfere with food web ecology and ecosystem balance.

Toxicity of the 3,4-Methylenedioxymethamphetamine and Its Enantiomers to Daphnia magna after Isolation by Semipreparative Chromatography

MDMA (3,4-methylenedioxymethamphetamine) is a chiral psychoactive recreational drug sold in illicit markets as racemate. Studies on the impact of MDMA on aquatic organisms are scarce. While enantioselectivity in toxicity in animals and humans has been reported, none is reported on aquatic organisms. This study aimed to investigate the ecotoxicological effects of MDMA and its enantiomers in Daphnia magna. For that, enantiomers (enantiomeric purity > 97%) were separated by liquid chromatography using a homemade semipreparative chiral column. Daphnids were exposed to three concentrations of (R,S)-MDMA (0.1, 1.0 and 10.0 µg L^-1) and two concentrations of (R)- and (S)-enantiomers (0.1 and 1.0 µg L^-1) over the course of 8 days. Morphophysiological responses were dependent on the substance form and daphnia development stage, and they were overall not affected by the (R)-enantiomer. Changes in swimming behaviour were observed for both the racemate and its enantiomers, but enantioselective effects were not observed. Reproductive or biochemical changes were not observed for enantiomers whereas a significant decrease in acetylcholinesterase and catalase activity was noted at the highest concentration of (R,S)-MDMA (10 µg L^-1). Overall, this study showed that sub-chronic exposure to MDMA racemate and its enantiomers can interfere with morphophysiological and swimming behaviour of D. magna. In general, the (R)-enantiomer demonstrated less toxicity than the (S)-enantiomer.

Chronic and transgenerational effects of silver nanoparticles in freshwater gastropod Lymnaea stagnalis

Traditional ecotoxicological studies prove to be focused mainly on single-generation, multigenerational research in ecotoxicological testing is needed to improve the predictive approaches in ecological risk assessment. Silver nanoparticles (AgNPs) have been increasingly detected in aquatic environments due to their extensive use in consumer products. We investigated the transgenerational effects of AgNPs on the life traits of freshwater model gastropods Lymnaea stagnalis for two generations. The reversibility of the effects of using recovery experiments was also performed. Results showed that AgNPs induced high Ag bioaccumulation in the whole soft tissues of parental L. stagnalis after 21 days of exposure. The increased ROS production and reduced condition index and fecundity were found after exposure to AgNPs at 500 μg/L. These results highlight that under AgNPs exposure, adult gastropods might allocate more resources to resist oxidative stress rather than to growth or reproduction. Furthermore, the Ag accumulation and ROS production of egg clutches were significantly related to parental exposure duration and concentrations. On the other hand, isolated eggs exposure demonstrated biological effects were persistent in terms of the next generation. For example, after transfer to a clean medium, similar Ag bioaccumulation and ROS production were observed from eggs which parents were pre-exposed to 50 and 500 μg/L AgNPs. Current explicit consideration of offspring performance adds value to existing toxicity testing protocols. Parental exposure duration has important implications for offspring effects, and parental exposure can cause transgenerational changes in resistance that have significant implications for toxicity testing and adaptive responses. These effects across generations point out the need for multigenerational tests to assess the environmental risk of MNPs in aquatic organisms.

Ecological Risk Analysis for Benzalkonium Chloride, Benzethonium Chloride, and Chloroxylenol in US Disinfecting and Sanitizing Products

Use of three topical antiseptic compounds-benzalkonium chloride (BAC), benzethonium chloride (BZT), and chloroxylenol (PCMX)-has recently increased because of the phaseout of other antimicrobial ingredients (such as triclosan) in soaps and other disinfecting and sanitizing products. Further, use of sanitizing products in general increased during the coronavirus (COVID-19) pandemic. We assessed the environmental safety of BAC, BZT, and PCMX based on best available environmental fate and effects data from the scientific literature and privately held sources. The ecological exposure assessment focused on aquatic systems receiving effluent from wastewater-treatment plants (WWTPs) and terrestrial systems receiving land-applied WWTP biosolids. Recent exposure levels were characterized based on environmental monitoring data supplemented by modeling, while future exposures were modeled based on a hypothetical triclosan replacement scenario. Hazard profiles were developed based on acute and chronic studies examining toxicity to aquatic life (fish, invertebrates, algae, vascular plants) and terrestrial endpoints (plants, soil invertebrates, and microbial functions related to soil fertility). Risks to higher trophic levels were not assessed because these compounds are not appreciably bioaccumulative. The risk analysis indicated that neither BZT nor PCMX in any exposure media is likely to cause adverse ecological effects under the exposure scenarios assessed in the present study. Under these scenarios, total BAC exposures are at least three times less than estimated effect thresholds, while margins of safety for freely dissolved BAC are estimated to be greater than an order of magnitude. Because the modeling did not specifically account for COVID-19 pandemic-related usage, further environmental monitoring is anticipated to understand potential changes in environmental exposures as a result of increased antiseptic use. The analysis presented provides a framework to interpret future antiseptic monitoring results, including monitoring parameters and modeling approaches to address bioavailability of the chemicals of interest. Environ Toxicol Chem 2022;41:3095-3115. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Acute toxicity characterization of organic UV-filters and chronic exposure revealing multigenerational effects in DAPHNIA MAGNA

Organic ultraviolet (UV) filters have often been detected in aquatic ecosystems in concentrations ranging from ng/L to μg/L. However, both their acute and chronic effects on aquatic organisms have been insufficiently explored. This study aimed to evaluate acute toxicity of some of the main UV filters used worldwide (2-ethylhexyl,4-methoxycinnamate/EHMC, avobenzone/AVO, benzophenone-3/BP-3, and octocrylene/OC), in three aquatic organisms (Artemia salina, Desmodesmus subspicatus, and Daphnia magna), and to further investigate multigenerational effects in D. magna. After acute toxicity was confirmed, daphnids were chronically exposed to environmentally relevant concentrations of UV filters for two consecutive generations (F0 and F1), and reproductive endpoints, as well as catalase (CAT) and glutathione-S-transferase (GST) activities, were assessed. EHMC showed the most toxic potential, with the lowest EC₅₀ values for the three organisms. On the other hand, reproductive delays and a decrease in the reproduction rate were observed in the F1 generation exposed to AVO (4.4 µg/L), BP-3 (0.17 µg/L), EHMC (0.2 µg/L), and MIX. An increase of the CAT activity in organisms exposed to BP-3 and EHMC suggested induction of the antioxidant system. Although no reproductive effect was observed in the first generation, toxic effects obtained in the F1 revealed the importance of multigenerational studies and the potential harm of UV filters to the life cycle of D. magna, even at environmentally relevant concentrations. This emphasizes the need for further studies considering these levels of exposure and more realistic experimental designs to better understand their potential risks. Environmentally relevant concentrations of Organic UV filters are not lethal to aquatic organisms, however may affect reproductive parameters in Daphnia magna though multigenerational exposures.

Antiparasitic potential of agrochemical fungicides on a non-target aquatic model (Daphnia × Metschnikowia host-parasite system)

Pesticides are a major anthropogenic threat to the biodiversity of freshwater ecosystems, having the potential to affect non-target aquatic organisms and disrupt the processes in which they intervene. Important knowledge gaps have been recognised concerning the ecological effects of synthetic fungicides on non-target symbiotic aquatic fungi and the ecological processes where they intervene. The goal of this work was to assess the influence of three commonly used fungicides (myclobutanil, metalaxyl and cymoxanil), which differ in their mode of action, on a host (the crustacean Daphnia magna) × parasite (the yeast Metschnikowia bicuspidata) experimental model. Using a set of life history experiments, we evaluated the effect of each fungicide on the outcome of this relationship (disease) and on the fitness of both host and parasite. Contrasting results were observed: (i) cymoxanil and metalaxyl were overall innocuous to host and parasite at the tested concentrations, although host reproduction was occasionally reduced in the simultaneous presence of parasite and fungicide; (ii) on the contrary, myclobutanil displayed a clear antifungal effect, decreasing parasite prevalence and alleviating infection signs in the hosts. This antiparasitic effect of myclobutanil was further investigated with a follow-up experiment that manipulated the timing of application of the fungicide, to understand which stage of parasite development was most susceptible: while myclobutanil did not interfere in the early stages of infection, its antifungal activity was clearly observable at a later stage of the disease (by impairing the production of transmission stages of the parasite). More research is needed to understand the broader consequences of this parasite-clearance effect, especially in face of increasing evidence that parasites are ecologically more important than their cryptic nature might suggest.

Multi- and Trans-Generational Effects on Daphnia Magna of Chlorpyrifos Exposures

Chlorpyrifos, a broad-spectrum neurotoxic organophosphate insecticide, is subject to atmospheric and hydrolytic transport from application sites to aquatic ecosystems. Across the landscape, concentrations in surface water can vary spatially and temporally according to seasonal use practices. Standardized bioassays can provide a screening-level understanding of aquatic receptor acute and chronic toxicity. However, these bioassays do not address ecologically relevant exposure patterns that may impact fitness and survival within and across generations. The aim of the present study was to evaluate the utility of a second-tier, screening-level methodology employing Daphnia magna multi- and transgenerational bioassays spanning four generations to investigate the effect of variable chronic chlorpyrifos exposure. The multigenerational assay consisted of continuous chlorpyrifos exposure across four consecutive 21-day bioassays using progeny from the previous assay for each successive generation. In the transgenerational assay, only the parent (F0) generation was exposed. For both assays, survival and reproduction were assessed across treatments and generations. Results indicated that (1) following continuous chlorpyrifos exposure at ecologically relevant concentrations to four generations of D. magna, the highest treatment showed an apparent tolerance response for both survival and reproductive success in the F3 generation, and (2) chlorpyrifos exposure to the F0 generation did not result in treatment effects in the unexposed F1, F2, and F3 generations in the apical endpoints of survival and reproduction. Employing a suite of acute and chronic bioassays, including chronic exposures spanning multiple generations, allows for a more robust screening-level evaluation of the potential impact of chlorpyrifos on aquatic receptors for variable periods of exposure. Environ Toxicol Chem 2022;41:1054-1065. © 2021 SETAC.

Transcriptomic Alterations in Water Flea (Daphnia magna) following Pravastatin Treatments: Insect Hormone Biosynthesis and Energy Metabolism

Pravastatin, used for lowering cholesterol and further decreasing blood lipid, has been frequently detected in the contaminated freshwaters, whereas its long-term exposure effects on non-target aquatic invertebrates remains undetermined. Therefore, the purpose of this study was to evaluate the toxic effects of pravastatin (PRA) with the concentration gradients (0, 0.5, 50, 5000 μg/L) on a model water flea Daphnia magna (D. magna) over 21 d based on phenotypic and genome-wide transcriptomic analyses. After 21 d, exposure to PRA at 5000 μg/L significantly reduced the body length and increased the number of offspring. The 76, 167, and 499 differentially expressed genes (DEGs) were identified by using absolute log2 fold change < 1 and adj p < 0.05 as a cutoff in the 0.5, 50, and 5000 μg/L PRA treatment groups, respectively. Three pathways, including xenobiotic metabolism, insect hormone biosynthesis pathway, and energy metabolism were significantly (p < 0.05) enriched after exposure to PRA. These suggested that the upregulation of genes in insect biosynthetic hormone pathway increased the juvenile hormone III content, which further reduced the body length of D. magna. The positive effect of methyl farnesoate synthesis on the ovarian may result in the increased number of offspring. Furthermore, energy tended to be allocated to detoxification process and survival under stress conditions, as the amount of energy that an individual can invest in maintenance and growth is limited. Taken together, our results unraveled the toxic mechanism of cardiovascular and lipid pharmaceuticals in aquatic invertebrate.

Individual and mixed effects of anticancer drugs on freshwater rotifers: A multigenerational approach

Human population growth has led to an increased release of chemical contaminants into aquatic environments. Emerging chemical contaminants (ECCs) are of increasing concern because they can affect non-target organisms in aquatic ecosystems. The application of anticancer drugs is increasing because of enhanced cancer rates and use of chemotherapy. We assessed the impacts of two widely used anticancer drugs known for their distinct modes of action, namely 5-fluorouracil (5-FU) and doxorubicin (DOX), on the freshwater rotifer Brachionus calyciflorus across generations. Rotifer mortality (24 h) and population growth (48 h) were assessed to determine initial lethal and sub-lethal effects. Exposure of rotifers to 5-FU (up to 200 mg L^-1) did not cause mortality, while DOX caused mortality at high concentrations (EC₅₀ = 15.6 mg L^-1). Effects of 5-FU on population growth rate was higher than DOX (5-FU EC₅₀ =10.49 µg L^-1, DOX EC₅₀ = 8.78 mg L^-1). The effects of the drugs in binary mixture on population growth rates were dose dependent; significant antagonistic effects were found when 5-FU was present in the mixture at high concentrations. Finally, a transgenerational assay for five generations revealed that rotifers were able to recover their population growth rate after fourth generation when exposed to 5-FU; however, population became non-viable after the second generation of exposure to DOX. At the cellular level, accumulation of reactive oxygen species and plasma membrane damage were observed at EC₁₀ and increased at EC₅₀ for both drugs. After exposure of rotifers to 5-FU across generations, there were signs of oxidative stress recovery, as shown by a decrease in ROS accumulation and plasma membrane damage. Our results showed for the first time that the adverse effects of anticancer drugs on freshwater rotifer populations are drug and dose dependent and can persist or be attenuated along generations.

Effects of metal nanoparticles on freshwater rotifers may persist across generations

Nanotechnology has become one of the fastest growing industries in the current century because nanomaterials (NMs) are present in an ever-expanding range of consumer products increasing the chance of their release into natural environments. In this study, the impacts of two metal nanoparticles (Ag-NPs and CuO-NPs) and their equivalent ionic forms (Ag⁺ and Cu²⁺) were assessed on the lentic freshwater rotifer Brachionus calyciflorus and on its ability to adapt and recover through generations. In our study, Ag-NPs and CuO-NPs inhibited the rotifer population growth rate and caused mortality at low concentrations (< 100 μg L^-1). Ag-NPs and CuO-NPs decreased in the medium when organisms were present (48 h exposure: 51.1 % and 66.9 %, respectively), similarly Ag⁺ and Cu²⁺ also decreased from medium in presence of the organisms (48 h: 35.2 % and 47.3 %, respectively); although the metal concentrations removed from the medium were higher for nanoparticles than metal ions, metal ions showed higher effects then their respective nanoparticle forms. Rotifer populations exposed for 4 generations to the toxicants were able to recover the population growth rate, but some rotifers showed developmental delay and inability to reproduce even after the removal of the toxicants. Intracellular accumulation of reactive oxygen species as well as plasma membrane damage were found in the rotifers at concentrations corresponding to EC₁₀ (Ag-NPs = 1.7 μg L^-1, Ag⁺ = 4.5 μg L^-1, CuO-NPs = 46.9 μg L^-1, Cu²⁺ = 35 μg L^-1) of the population growth rate. Our results showed, for the first time, that effects of metal nanoparticles and metal ions on rotifer populations may persist along several generations. This should be taken into account when assessing risks of metal nanoparticles in freshwaters.

A "Population Dynamics" Perspective on the Delayed Life-History Effects of Environmental Contaminations: An Illustration with a Preliminary Study of Cadmium Transgenerational Effects over Three Generations in the Crustacean Gammarus

We explore the delayed consequences of parental exposure to environmentally relevant cadmium concentrations on the life-history traits throughout generations of the freshwater crustacean Gammarus fossarum. We report the preliminary results obtained during a challenging one-year laboratory experiment in this environmental species and propose the use of population modeling to interpret the changes in offspring life-history traits regarding their potential demographic impacts. The main outcome of this first long-term transgenerational assay is that the exposure of spawners during a single gametogenesis cycle (3 weeks) could result in severe cascading effects on the life-history traits along three unexposed offspring generations (one year). Indeed, we observed a decrease in F1 reproductive success, an early onset of F2 offspring puberty with reduced investment in egg yolk reserves, and finally a decrease in the growth rate of F3 juveniles. However, the analysis of these major transgenerational effects by means of a Lefkovitch matrix population model revealed only weak demographic impacts. Population compensatory processes mitigating the demographic consequences of parental exposure seem to drive the modification of life-history traits in offspring generations. This exploratory study sheds light on the role of population mechanisms involved in the demographic regulation of the delayed effects of environmental toxicity in wild populations.

Transgenerational toxicity of flumequine over four generations of Daphnia magna

In this study, the effects of both continuous and alternate exposure to 2 mg L^-1 of flumequine (FLU) on survival, growth and reproduction of Daphnia magna were evaluated over four generations. Mortality was the most evident effect, with an average mortality rate of 23 ± 14% across generations. Individuals destined to succumb were identifiable well in advance through their discolouration and lack of development, and limited or zero reproductive capacity. Inhibition of reproduction in surviving mothers varied across the four generations (14.3 ± 17%) without an apparent correlation with the duration of exposure over generations. Significant reproductive inhibition was observed in the generation that followed three non-exposed generations (the fourth generation), pointing to a transgenerational toxicity of FLU. In another experiment, in vitro exposure of 72 D. magna embryos to 2 mg L^-1 FLU caused 14% mortality (versus 7% in the control). Among the 62 individuals that hatched alive, six showed birth defects and only one was able to survive the next few days. The other, apparently healthy newborns were randomly assigned to two groups and submitted to a reproduction test, either in the absence or in the presence of 2 mg L^-1 FLU. A high mortality rate and/or strongly significantly inhibited reproduction were detected in both groups. As with previously run analogous tests with enrofloxacin, the multigenerational and embryonic tests showed a clear disruption to this crustacean population which would not be evidenced by the standard official acute and chronic tests. This indicates the necessity of taking a different and more comprehensive approach to the evaluation of substances having an inherent ability to interact with genetic material.

Physical and chemical characterization of natural and modified nanoclays and their ecotoxicity on a freshwater algae species (Chlamydomonas reinhardtii)

Nanoclays represent a class of natural and modified nanomaterials that have received attention from industrial and environmental fields. Studies that assess the physicochemical properties of nanoclays and compare the effects of natural and modified nanoclays are scarce. We assessed the physicochemical characteristics of a natural nanoclay (Na⁺ montmorillonite) and 2 modified nanoclays (Cloisite® 30B and Novaclay™) in the dry powder state and in solution, and their potential toxic effects on algal population growth (Chlamydomonas reinhardtii). All 3 nanoclays exhibited properties that are thought to cause toxic effects on organisms, but the properties varied among the nanoclays. Cloisite 30B had a low particle stability and a chemical composition that are thought to induce a greater toxic effect on organisms than either Novaclay or natural nanoclay. In contrast, Novaclay and natural nanoclay had a particle shape (nanoplate) in solution that is thought to induce a greater toxic effect on organisms than the type of particle shape (spherical) that Cloisite 30B has in solution. Cloisite 30B suppressed population growth of C. reinhardtii, an effect that increased with dosage. Neither Novaclay nor natural nanoclay affected algal population growth across a broad array of concentrations. The results show that modified nanoclays differ in their impact on algae, and careful thought must be given to their usage because some will have negative consequences if released into aquatic ecosystems. Environ Toxicol Chem 2018;37:2860-2870. © 2018 SETAC.