Using a multibiomarker approach and behavioural responses to assess the effects of anthracene in Palaemon serratus

Do zebrafish become blind or is it too much red dye in water? Distinguishing the embryo-larval development and physiology effects of DR 60, 73, and 78

Some dyes currently used by the textile, pharmaceutical, food, cosmetic, and photographic industries have been shown to be toxic and/or mutagenic to aquatic life. Most of these dyes resist degradation processes available for treating wastewater, and these processes might generate even more toxic by-products. Despite the large number of available dyes and the large quantity of dyes released into the environment, studies on their toxicity are still scarce. We evaluated and compared the effects in the animal model Danio rerio (zebrafish) of environmentally relevant concentrations of Disperse Red 60 (DR 60), 73 (DR 73), and 78 (DR 78) using the fish embryo acute toxicity (FET) test, morphometric analysis, immunofluorescence imaging, and behavioral parameters. DR 60 caused ocular modifications, while the DR 73 caused non-inflation of the swim bladder (NISB), pericardial edema (PE), scoliosis (S) and abnormal yolk sac (AYS) from at 0.125 mg/L. In behavioral tests, all the dyes induced changes in velocity and time spent swimming of exposed larvae. However, these alterations in behavior seem to be caused by different factors dependent on the dye and its concentration. Nevertheless, behavior seems to add valuable information concerning the hazards analysis of dyes, since it reveals to be the most sensitive group of parameters tested in the current study. In conclusion, of the behavioral and developmental alterations caused by these dyes should be interpreted as an alert for greater attention when registering new dyes and releasing them into the environment. In the particular case of DR 60 the possibility that directly affects the eye of larvae is of great environmental concern, but also from the human health perspective.

Emerging studies on oil pollution biomonitoring: A systematic review

In the last decade, several methods were applied to monitor the impact of oil pollution on marine organisms. Recent studies showed an eminent need to standardize these methods to produce comparable results. Here we present the first thorough systematic review of the literature on oil pollution monitoring methods in the last decade. The literature search resulted on 390 selected original articles, categorized according to the analytical method employed. Except for Ecosystem-level analyses, most methods are used on short-term studies. The combination of Biomarker and Bioaccumulation analysis is the most frequently adopted strategy for oil pollution biomonitoring, followed by Omic analyses. This systematic review describes the principles of the most frequently used monitoring tools, presents their advantages, limitations, and main findings and, as such, could be used as a guideline for future researches on the field.

Transcriptomic and Histological Analysis of the Greentail Prawn (Metapenaeus bennettae) Following Light Crude Oil Exposure

Oil spills pose a significant threat to marine biodiversity. Crude oil can partition into sediments where it may be persistent, placing benthic species such as decapods at particular risk of exposure. Transcriptomic and histological tools are often used to investigate the effects of hydrocarbon exposure on marine organisms following oil spill events, allowing for the identification of metabolic pathways impacted by oil exposure. However, there is limited information available for decapod crustaceans, many of which carry significant economic value. In the present study, we assess the sublethal impacts of crude oil exposure in the commercially important Australian greentail prawn (Metapenaeus bennettae) using transcriptomic and histological analyses. Prawns exposed to light, unweathered crude oil "spiked" sediments for 90 h were transferred to clean sediments for a further 72 h to assess recovery. Chemical analyses indicated that polycyclic aromatic hydrocarbons increased by approximately 65% and 91% in prawn muscle following 24 and 90 h of exposure, respectively, and significantly decreased during 24- and 72-h recovery periods. Transcriptomic responses followed an exposure and recovery pattern with innate immunity and nutrient metabolism transcripts significantly lowered in abundance after 24 h of exposure and were higher in abundance after 72 h of recovery. In addition, transcription/translation, cellular responses, and DNA repair pathways were significantly impacted after 24 h of exposure and recovered after 72 h of recovery. However, histological alterations such as tubule atrophy indicated an increase in severity after 24 and 72 h of recovery. The present study provides new insights into the sublethal impacts of crude oil exposure in greentail prawns and identifies molecular pathways altered by exposure. We expect these findings to inform future management associated with oil extraction activity and spills. Environ Toxicol Chem 2022;41:2162-2180. © 2022 John Wiley & Sons Ltd. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

The Role of the Ecotoxicology Applied to Seafood as a Tool for Human Health Risk Assessments Concerning Polycyclic Aromatic Hydrocarbons

Background: Polycyclic aromatic hydrocarbons (PAHs) are persistent pollutants routinely detected in aquatic ecosystems. It is, therefore, necessary to assess the link between deleterious marine biota PAH effects, especially in commercialized and consumed animals, environmental health status, and potential human health risks originating from the consumption of contaminated seafood products. Thus, this review seeks to verify the relationships of ecotoxicological studies in determining effect and safety concentrations on animals routinely consumed by humans. Methods: A total of 52 published studies between 2011 and 2021, indexed in three databases, were selected following the PICO methodology, and information on test animals, evaluated PAH, and endpoints were extracted. Results: Benzo(a)pyrene and phenanthrene were the most investigated PAHs in terms of biomarkers and test organisms, and mussels were the most evaluated bioindicator species, with an emphasis on reproductive responses. Furthermore, despite the apparent correlation between environmental PAH dynamics and effects on aquatic biota and human health, few assessments have been performed in a multidisciplinary manner to evaluate these three variables together. Conclusions: The links between human and environmental sciences must be strengthened to enable complete and realistic toxicity assessments as despite the application of seafood assessments, especially to mussels, in bioassays, the connection between toxicological animal responses and risks associated with their consumption is still understudied.

Lethal, behavioral, growth and developmental toxicities of alkyl-PAHs and non-alkyl PAHs to early-life stage of brine shrimp, Artemia parthenogenetica

Alkyl-PAHs are the predominant form of PAHs in crude oils which are supposed to demonstrate different toxicities compared to non-alkyl PAHs. Little information is available about the toxicity of alkyl-PAHs on marine Artemia. This study addressed and compared the lethal, behavioral, growth and developmental toxicities of three alkyl-PAHs, namely 3-methyl phenanthrene (3-mPhe), retene (Ret) and 2-methyl anthracene (2-mAnt), to their non-alkyl forms, phenanthrene (Phe) and anthracene (Ant) using Artemia parthenogenetica (nauplii, <24 h) as test organism following a 48 h and a 7 d of exposure, respectively. Benzo-a-pyrene (Bap) was selected as a reference toxicant for the comparison with the above alkyl-PAHs and non-alkyl PAHs. Results showed that for all tested endpoints, A. parthenogenetica nauplii had the highest sensitivity to Bap while Ant had no significant effect on nauplii survival or development within given concentrations. Considering the aqueous freely dissolved PAH concentrations, the 48 h-LC₅₀ (survival), 48 h-EC₅₀ (immobility) and 7 d-LC₁₀ (survival) of Bap were calculated as 0.321, 0.285 and 0.027 μg/L, respectively, which were twofold to fivefold lower than those of Phe, 3-mPhe, Ret, Ant and 2-mAnt. A higher acute toxicity of alkyl-PAHs (3-mPhe and 2-mAnt) than their non-alkyl forms (Phe and Ant) was observed. Not limited to Phe, the common non-polar narcotic mode of action was also observed for Bap, 3-mPhe, Ret and 2-mAnt, which was evident by the inhibited mobility of nauplii. The decreased body lengths were found for all PAH treatments compared to the solvent control, whereas instar retardations were only found in nauplii exposed to Bap, Phe and Ret. Our findings emphasized the sensitivity differences of A. parthenogenetica nauplii to selected alkyl PAHs and non-alkyl PAHs and confirmed the application of lethal, behavioral and growth indicators in the toxicity evaluation of selected PAHs other than Ant. However, the distinct toxicities of these PAHs suggested other toxic modes of action may play more important roles apart from narcotic mode of action and need to be elucidated in future studies. In addition, a strong correlation between the body length and the instar of A. parthenogenetica nauplii was observed for each PAH exposure, suggesting that body length can be representative for both growth and developmental indicators during biological monitoring of PAH pollution in marine environment.

Effects of pyrene and benzo[a]pyrene on the reproduction and newborn morphology and behavior of the freshwater planarian Girardia tigrina

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants of aquatic ecosystems. Because they are persistent, there is great potential for chronic toxicity to aquatic species, and the evaluation of reproductive effects is fundamental. In this context, planarians are interesting experimental animals, since they can be sensitive to environmental pollutants, and a wide range of reproductive-related endpoints can be assessed. In this work we evaluated fecundity (number of cocoons), fertility (number of newborns), newborn anomalies, adult weight, regenerative abilities and PAH-residues in tissues of the freshwater planarian Girardia tigrina, exposed to either pyrene or benzo[a]pyrene (B[a]P). Pyrene reduced planarian fecundity and fertility at 18.75 μg L^-1 and 75.00 μg L^-1, while B[a]P reduced planarian fecundity at the 37.50 μg L^-1 treatment, which was accompanied by a 33.7% reduction in fertility. Cocoons were kept in clean media and newborns were evaluated for behavioral and morphological anomalies. Many of the newborns resulting from the B[a]P experiment revealed behavioral anomalies, such as spasms and uncoordinated movements. These behavioral anomalies were observed in 12.9% and 38.2% of newborns resulting from the exposure of adult planarians to 9.38 μg L^-1 and 37.50 μg L^-1 of B[a]P, respectively. This study is the first report on the effects of PAHs in freshwater planarians' sexual reproduction and a decreased reproductive output was evidenced. Moreover, the exposure of adults to B[a]P lead to defects in newborns, raising concern on the possible long-term consequences of these compounds for natural planarian populations.

Toxicity of different polycyclic aromatic hydrocarbons (PAHs) to the freshwater planarian Girardia tigrina

Freshwater planarians have been gaining relevance as experimental animals for numerous research areas given their interesting features, such as high regeneration potential, shared features with the vertebrates' nervous system or the range of endpoints that can be easily evaluated in response to contaminants. Ecotoxicological research using these animals has been steadily increasing in the past decades, as planarians' potentialities for this research area are being recognized. In this work, we used polycyclic aromatic hydrocarbons (PAHs) as model contaminants and evaluated effects of exposure to phenanthrene, pyrene and benzo[a]pyrene (B[a]P) in planarians. The freshwater planarian Girardia tigrina was chosen and mortality, cephalic regeneration (during and post-exposure), behavioral endpoints and presence of PAHs in tissues, were evaluated. Mortality was only observed in planarians exposed to phenanthrene, with an estimated LC₅₀ of 830 μg L^-1. Results indicate that planarian behavioral endpoints were very sensitive in response to sub-lethal concentrations of PAHs, showing a greater sensitivity towards B[a]P and pyrene. Briefly, post-exposure locomotion and post-exposure feeding were significantly impaired by sub-lethal concentrations of all compounds, whereas regeneration of photoreceptors was only significantly delayed in planarians exposed to pyrene. Moreover, levels of PAH-type compounds in planarian tissues followed a concentration-dependent increase, showing uptake of compounds from experimental solutions. The present results highlight the importance of studying alternative and complementary endpoints, such as behavior, not only because these may be able to detect effects at lower levels of contamination, but also due to their ecological relevance. The simplicity of evaluating a wide range of responses to contaminants further demonstrates the utility of freshwater planarians for ecotoxicological research.

Toxicity of dyes to zebrafish at the biochemical level: Cellular energy allocation and neurotoxicity

Dyes are widely distributed worldwide, and can be found in wastewaters resulting from industrial or urban effluents. Dyes are of particular concern as contaminants of the aquatic environment, since their toxicity remain poorly understood. Thus, the current study was designed to assess the effects induced by the synthetic azo dye Basic Red 51 (BR51) and by the natural naphthoquinone dye erythrostominone (ERY) on zebrafish early life stages (Danio rerio) at different biological organization levels, i.e., studying how changes in biochemical parameters of important physiological functions (neurotransmission and cellular energy allocation) may be associated with behavior alterations (swimming activity). This approach was also used to assess the effects of ERY after its photodegradation resulting in a colorless product(s) (DERY). Results showed that after 96 h exposure to BR51 and Ery, zebrafish embryos consumed less energy (LOEC = 7.5 mg/L), despite the unaltered levels of available energy (carbohydrates, lipids and proteins). Hence, cellular energy allocation (CEA) was significantly increased. On the other hand, only ERY decreased the acetylcholinesterase activity (LOEC = 15 mg/L). Despite that, zebrafish larvae exposed to both dyes until 144 h were less active. In contrast, DERY did not affect any parameter measured. These results indicate an association between a decrease consumption of energy and decrease swimming activity resulting from an environmental stress condition, independently of the neurotoxicity of the dyes. Degradation of ERY by light prevented all toxic effects previously observed, suggesting a cheap, fast and easy alternative treatment of effluents containing this natural dye. All tools assessed in our current study were sensitive as early-warning endpoints of dyes toxicity on zebrafish early life stages, and suggest that the CEA assay might be useful to predict effects on locomotor activity when cholinergic damage is absent.

Biochemical approaches to assess oxidative stress induced by exposure to natural and synthetic dyes in early life stages in zebrafish

Zebrafish early life stages were found to be sensitive to several synthetic dyes widely used in industries. However, as environmental concentrations of such contaminants are often at sublethal levels, more sensitive methods are required to determine early-warning adverse consequences. The aim of this study was to utilize a multibiomarker approach to examine underlying oxidative stress mechanisms triggered by sublethal concentrations of synthetic azo dye Basic Red 51 (BR51), the natural dye erythrostominone (ERY), and its light-degraded product using zebrafish embryos. Biochemical biomarkers included parameters of detoxification and markers of antioxidant system, as well as oxidative damage. Results showed pro-oxidant mechanisms attributed to BR51 and ERY as evidenced by increased glutathione S-transferase (GST) activity, a phase II detoxification enzyme related to reactive oxygen species detoxification. BR51 also elevated total glutathione (GSH+GSSG) levels and catalase activity. However, both dyes induced oxidative damage as evidenced by elevated lipid peroxidation content. In contrast, when the natural dye was photodegraded, no marked effects were observed for all biomarkers assessed. Data indicate that such dyes are pro-oxidants at sublethal concentrations, predominantly involving GSH and/or related enzymes pathway.

Old model organisms and new behavioral end-points: Swimming alteration as an ecotoxicological response

Behavioral responses of aquatic organisms have received much less attention than developmental or reproductive ones due to the scarce presence of user-friendly tools for their acquisition. The technological development of data acquisition systems for quantifying behavior in the aquatic environment and the increase of studies on the understanding the relationship between the behavior of aquatic organisms and the physiological/ecological activities have generated renewed interest in using behavioral responses also in marine ecotoxicology. Recent reviews on freshwater environment show that behavioral end-points are comparatively fast and sensitive, and warrant further attention as tools for assessing the toxicological effects of environmental contaminants. In this mini-review, we perform a systematic analysis of the most recent works that have used marine invertebrate swimming alteration as behavioral end-point in ecotoxicological studies by assessing the differences between behavioral and acute responses in a wide range of species, in order to compare their sensitivity.

Release of anthracene from estuarine sediments by crab bioturbation effects

To investigate bioturbation effects on anthracene (Ant) release from sediments to the overlying water, indoor microcosms were developed. Naturally contaminated estuarine sediments were exposed to the crab Helice tiensinensis over 70 days and compared with sediments with no crab. Bioturbation by crab could significantly increase the release of both particulate and dissolved Ant. The releases of particulate Ant with bioturbation treatments were 2.3-11.7 times higher than in the control treatments. However, the releases of dissolved Ant with bioturbation treatments were 1.7-3.7 times higher than in the control treatments. The ratio of particulate Ant/total Ant varied from 89 % to 98 % in the bioturbation treatments, which was significantly higher than in the control treatments. These results indicate that crab bioturbation significantly enhanced both particulate and dissolved Ant release from sediment, but the particulate Ant is the predominant process.

Acute toxicity of dichloroacetonitrile (DCAN), a typical nitrogenous disinfection by-product (N-DBP), on zebrafish (Danio rerio)

Dichloroacetonitrile (DCAN) is a typical nitrogenous disinfection by-product (N-DBP) and its toxicity on aquatic animals is investigated for the first time. The present study was designed to investigate the potential adverse effects of DCAN on zebrafish. DCAN could induce developmental toxicity to zebrafish embryos. A significant decrease in hatchability and an increase in malformation and mortality occurred when DCAN concentration was above 100µg/L. Heart function alteration and neuronal function disturbance occurred at concentration higher than 500 and 100µg/L, respectively. Further, DCAN was easily accumulated in adult zebrafish. The rank order of declining bioconcentration factor (BCF) was liver (1240-1670)> gill (1210-1430)> muscle (644-877). DCAN caused acute metabolism damage to adult zebrafish especially at 8 days exposure, at which time the "Integrated Biomarker Response" (IBR) index value reached 798 at 1mg/L DCAN dose. Acute DNA damage was induced to adult zebrafish by DCAN even at 10µg/L dose.

Behavioral and biochemical responses in freshwater fish Carassius auratus exposed to sertraline

Sertraline is one of the most commonly prescribed selective serotonin reuptake inhibitors and is frequently detected in the aquatic environment. However, knowledge regarding relationships among molecular or biochemical endpoints involved in modes of action (MOAs) of sertraline and ecologically important behavioral responses of fish is insufficient. The present study aimed to investigate the bioconcentration and possible adverse outcomes pathways (AOPs) in crucian carp (Carassius auratus) exposed to various concentrations of sertraline (4.36, 21.3 and 116 μg L(-1)) for 7 d. Bioconcentration factor values were in the range of 19.5-626 in liver, 6.94-285 in brain, 4.01-146 in gill and 0.625-43.1 in muscle during the entire period of exposure. Liver superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) activities and brain acetylcholinesterase (AChE) activity were selected as biochemical endpoints associated with MOAs. Swimming activity, shoaling, feeding rate and food consumption were determined to assess behavioral responses. Fish plasma levels of sertraline exceeding human therapeutic doses were also predicted from external exposure concentrations. Significant enhancements in CAT, GPx, AChE and swimming activities and decreases in shoaling tendency, feeding rate and food consumption were observed when fish plasma levels exceeded human therapeutic thresholds. Shoaling, feeding rate and food consumption were correlated with the activities of SOD, CAT and GST. A significant positive correlation between swimming activity and AChE activity was also observed. As such, our study provides important AOPs linking biochemical responses with ultimate ecologically relevant behavioral endpoints.

Inhibitory effects of pain relief drugs on neurological enzymes: implications on their potential neurotoxicity to aquatic animals

Pain relief medications commonly occur in the aquatic environment at measurable levels. While the neurotoxicity of pain relievers to higher vertebrates is currently known, little is known about their effects on aquatic animals. This study investigated the neurotoxicity of pain relievers to aquatic animals. We used three neurological enzymes, cholinesterase (ChE), adenosine triphosphatase (ATPase), and monoamine oxidase (MAO), from a freshwater planarian (Dugesia japonica) and green neon shrimp (Neocaridina denticulata) as biomarkers to examine the effects of pain relievers on in vitro activity. The activity of MAO and ChE, but not ATPase, was significantly inhibited by acetaminophen, but not by other pain relievers examined. It was likely that the inhibitory effects of acetaminophen on shrimp neurological enzymes were more severe than on the planarian. These findings suggest that acetaminophen is potentially neurotoxic to aquatic animals, at least in terms of neurotransmission disturbance.