Effects of estrogenic xenobiotics on molting of the water flea, Daphnia magna

Exploring BPA alternatives - Environmental levels and toxicity review

Bisphenol A alternatives are manufactured as potentially less harmful substitutes of bisphenol A (BPA) that offer similar functionality. These alternatives are already in the market, entering the environment and thus raising ecological concerns. However, it can be expected that levels of BPA alternatives will dominate in the future, they are limited information on their environmental safety. The EU PARC project highlights BPA alternatives as priority chemicals and consolidates information on BPA alternatives, with a focus on environmental relevance and on the identification of the research gaps. The review highlighted aspects and future perspectives. In brief, an extension of environmental monitoring is crucial, extending it to cover BPA alternatives to track their levels and facilitate the timely implementation of mitigation measures. The biological activity has been studied for BPA alternatives, but in a non-systematic way and prioritized a limited number of chemicals. For several BPA alternatives, the data has already provided substantial evidence regarding their potential harm to the environment. We stress the importance of conducting more comprehensive assessments that go beyond the traditional reproductive studies and focus on overlooked relevant endpoints. Future research should also consider mixture effects, realistic environmental concentrations, and the long-term consequences on biota and ecosystems.

Combined effects of microplastics and antibiotic-resistant bacteria on Daphnia magna growth and expression of functional genes

Microplastics could act as vectors for the transport of harmful bacteria, such as pathogens and antibiotic resistance bacteria (ARB), but their combined effects have not been reported yet. Here, ARB Shigella flexneri with sulfonamides resistance and micro-polystyrene (micro-PS) were used to investigate their possible combined effects on the growth and expression of functional genes in Daphnia magna. Results showed that micro-PS colonized with S. flexneri were ingested by D. magna and blocked in their intestine after 24 h exposure. Changes were observed in the life history and morphology of D. magna, as well as the expression of functional genes in all treatments, but with no difference in the survival rate. We also determined the expression of six functional genes involved in energy and metabolism (arginine kinase, AK) and oxidative stress response (thioredoxin reductase, TRxR, catalase, CAT, and glutathione S-transferases, GSTs), as well as in growth, development and reproduction (vitellogenin, Vtg1 and ecdysone receptor, EcR). AK and Vtg1 did not show significant differences, however, EcR was down-regulated and the other three genes (TRxR, CAT, GSTs) were up-regulated in the combined-treated group. Antibiotic resistance gene (ARGs) sul1 was detected when exposed to micro-PS colonized with S. flexneri., suggesting that D. magna could acquire resistance genes through microplastic biofilms. These results indicated that MPs could act as a carrier of ARB to transfer ARGs into D. magna, and affect the life history, morphology, and the expression of related functional genes of D. magna, to adapt to the stress caused by MPs and ARB.

Evaluation of parental and transgenerational effects of clotrimazole in Daphnia magna - A multi-parametric approach

Azole antifungals inhibit the cytochrome P450 complex, decreasing the production of ergosterol in fungi, and compromising the biosynthesis of ecdysteroids in crustaceans, which are hormones regulating reproduction and ecdysis. The azole antifungal clotrimazole (CLO) raises environmental concerns due its toxicity. This work evaluated the effects on the number of moults, feeding rate, growth, reproduction, transgenerational reproductive effects on two different generations (F0, parental generation; and F1, organisms born from F0), and energetic balance in Daphnia magna. Neonates (<24 h) were exposed to sublethal concentrations (0, 2.7, and 3.4 mg/L) of CLO, to assess its effects on the moulting process. Neonates were also exposed to environmentally realistic concentrations of CLO (0, 30, 150, 750, and 3750 ng/L) for 24 and 96 h, to assess adverse effects on their feeding behaviour. Effects on energy reserves (fatty acids, glycogen, and protein levels) were also measured in animals exposed to CLO. A reproduction test was carried out to evaluate the amount and size of neonates from F0 and F1 generations. CLO exposure decreased the number of moults, and the size of organisms, but did not alter the feeding pattern of 5 days old individuals. However, neonates (<24 h) exposed to CLO had a significant decrease in their feeding pattern. CLO decreased the fatty acids content in exposed animals, but did not change glycogen and protein. CLO also decreased the size of adult daphnids from the third brood, born from animals exposed in F0; in F1 animals, the size of neonates from the third brood was decreased. This study evidenced the toxic effects caused by CLO on growth, feeding and reproduction of D. magna. Nevertheless, it is not possible to conclude whether the effects are due to the inhibition of cytochrome P450 enzymes, or to unspecific effects caused by general toxic stress and decreased nutrition.

The effects of ethylparaben and propylparaben on the development and fecundity of Drosophila melanogaster

Parabens are widely used as preservatives in pharmaceuticals, cosmetics, and food products. Ethylparaben (EP) and propylparaben (PP) are particularly preferred because of their bactericidal and fungicidal effects. Although generally described as safe compounds, many studies have reported that parabens have estrogenic and endocrine-disrupting properties. In the present study, the effects of EP and PP (50 mM, 100 mM and 200 mM) on Drosophila melanogaster development and fecundity were investigated. No differences were found in the pupation and maturation percentages in all concentrations of parabens (p > 0.05). However, it was found that the mean pupation and maturation times increased in all treatment groups (p < 0.05). A statistically significant decrease (p < 0.05) in the number of offspring of the 200 mM ethylparaben exposure group was observed. In all paraben groups, a significant reduction in mean fecundity was found compared to the control group (p < 0.05).

Effects of polyvinyl chloride microplastics on reproduction, oxidative stress and reproduction and detoxification-related genes in Daphnia magna

The drastic increase of microplastics (MPs) in aquatic environment has become a serious threat to marine and freshwater ecosystems. However, little information is available regarding the potential detrimental effects of polyvinyl chloride microplastics (PVC-MPs) on aquatic organisms. This study investigated the changes of reproduction parameters, oxidative stress and the expression of reproduction and detoxification-related genes in Daphnia magna after exposed to 2 ± 1 and 50 ± 10 μm PVC-MPs. The results showed that chronic exposure to 2 ± 1 μm PVC-MPs prolonged days to the first brood, increased total number of broods per female and frequency of molting per adult, decreased offspring number at first brood and total number of offspring per female in D. magna. Moreover, 2 ± 1 μm PVC-MPs also disturbed the activities of SOD and CAT, increased GSH and MDA levels. The expression of Vtg, SOD, CAT, CYP314 and CYP360A8 genes also exhibited different response patterns depending on exposure time. Furthermore, 50 ± 10 μm PVC-MPs decreased offspring at first brood and Vtg mRNA level, increased the transcription levels and activities of SOD and CAT. These results suggest that the presence of PVC-MPs in aquatic environment may cause reproduction toxicity by disrupting the reproduction and detoxification-related genes expression and inducing oxidative stress in D. magna.

Investigation of developmental and reproductive effects of resveratrol in Drosophila melanogaster

Resveratrol is a chemical that attracts attention due to its antioxidative, anti-inflammatory, and estrogenic/antiestrogenic properties. In the present study, it was aimed to investigate developmental and reproductive effects (developmental periods, average numbers of offspring, sex ratios) of resveratrol in Drosophila melanogaster. Their larvae were exposed to 50, 100, and 200 μM of resveratrol. Resveratrol treatments did not affect pupation and maturation rate (P ˃ 0.05) statistically. But the pupation and maturation times were significantly extended at all doses (P ˂ 0.05). Also, 100 and 200 μM resveratrol treatments resulted in a significant decrease in the number of offspring (P ˂ 0.05). The results reveal that resveratrol, which is generally known for its positive effects, may have negative effects on the development and reproduction of invertebrates. The results of this study support the idea that resveratrol may act as an endocrine disruptor, as it is a phytoestrogen.

Long-term exposure of Daphnia magna to polystyrene microplastic (PS-MP) leads to alterations of the proteome, morphology and life-history

In the past years, the research focus on the effects of MP on aquatic organisms extended from marine systems towards freshwater systems. An important freshwater model organism in the MP field is the cladoceran Daphnia, which plays a central role in lacustrine ecosystems and has been established as a test organism in ecotoxicology. To investigate the effects of MP on Daphnia magna, we performed a chronic exposure experiment with polystyrene MP under strictly standardized conditions. Chronic exposure of D. magna to PS microparticles led to a significant reduction in body length and number of offspring. To shed light on underlying molecular mechanisms induced by microplastic ingestion in D. magna, we assessed the effects of PS-MP at the proteomic level, as proteins, e.g., enzymes, are especially relevant for an organism's physiology. Using a state-of-the-art mass spectrometry based approach, we were able to identify 28,696 different peptides, which could be assigned to 3784 different proteins. Using a customized bioinformatic workflow, we identified 41 proteins significantly altered in abundance (q-value <0.05) in the PS exposed D. magna. Among the proteins increased in the PS treated group were several sulfotransferases, involved in basic biochemical pathways, as well as GABA transaminase catalyzing the degradation of the neurotransmitter GABA. In the abundance decreased group, we found essential proteins such as the DNA-directed RNA polymerase subunit and other proteins connected to biotic and inorganic stress and reproduction. Strikingly, we further identified several digestive enzymes that are significantly downregulated in the PS treated animals, which could have interfered with the affected animal's nutrient supply. This may explain the altered morphological and life history traits of the PS exposed daphnids. Our results indicate that long-term exposure to PS microplastics, which are frequently detected in environmental samples, may affect the fitness of daphnids.

Progestogen-induced alterations and their ecological relevance in different embryonic and adult behaviours of an invertebrate model species, the great pond snail (Lymnaea stagnalis)

The presence of oral contraceptives (basically applying estrogens and/or progestogens) poses a challenge to animals living in aquatic ecosystems and reflects a rapidly growing concern worldwide. However, there is still a lack in knowledge about the behavioural effects induced by progestogens on the non-target species including molluscs. In the present study, environmental progestogen concentrations were summarised. Knowing this data, we exposed a well-established invertebrate model species, the great pond snail (Lymnaea stagnalis) to relevant equi-concentrations (1, 10, 100, and 500 ng L-1) of mixtures of four progestogens (progesterone, drospirenone, gestodene, levonorgestrel) for 21 days. Significant alterations were observed in the embryonic development time, heart rate, feeding, and gliding activities of the embryos as well as in the feeding and locomotion activity of the adult specimens. All of the mixtures accelerated the embryonic development time and the gliding activity. Furthermore, the 10, 100, and 500 ng L-1 mixtures increased the heart rate and feeding activity of the embryos. The 10, 100, and 500 ng L-1 mixtures affected the feeding activity as well as the 1, 10, and 100 ng L-1 mixtures influenced the locomotion of the adult specimens. The differences of these adult behaviours showed a biphasic response to the progestogen exposure; however, they changed approximately in the opposite way. In case of feeding activity, this dose-response phenomenon can be identified as a hormesis response. Based on the authors' best knowledge, this is the first study to investigate the non-reproductive effects of progestogens occurring also in the environment on molluscan species. Our findings contribute to the global understanding of the effects of human progestogens, as these potential disruptors can influence the behavioural activities of non-target aquatic species. Future research should aim to understand the potential mechanisms (e.g., receptors, signal pathways) of progestogens induced behavioural alterations.

A Crab Is Not a Fish: Unique Aspects of the Crustacean Endocrine System and Considerations for Endocrine Toxicology

Crustaceans-and arthropods in general-exhibit many unique aspects to their physiology. These include the requirement to moult (ecdysis) in order to grow and reproduce, the ability to change color, and multiple strategies for sexual differentiation. Accordingly, the endocrine regulation of these processes involves hormones, receptors, and enzymes that differ from those utilized by vertebrates and other non-arthropod invertebrates. As a result, environmental chemicals known to disrupt endocrine processes in vertebrates are often not endocrine disruptors in crustaceans; while, chemicals that disrupt endocrine processes in crustaceans are often not endocrine disruptors in vertebrates. In this review, we present an overview of the evolution of the endocrine system of crustaceans, highlight endocrine endpoints known to be a target of disruption by chemicals, and identify other components of endocrine signaling that may prove to be targets of disruption. This review highlights that crustaceans need to be evaluated for endocrine disruption with consideration of their unique endocrine system and not with consideration of the endocrine system of vertebrates.

Invisible endocrine disruption and its mechanisms: A current review

The research on impacts of environmental chemicals on crustacean molting dates back to the 1970s when ground-breaking studies investigated the disruption of molting in Crustacea by organochlorines. With the emergence of a new scientific inquiry, termed environmental endocrine disruption, in the early 1990s, increasing attention has been attracted to the possibility that environmental chemicals capable of wreaking havoc on sex steroid-regulated processes in vertebrates can also adversely affect ecdysteroid-mediated processes, e.g. molting, in crustaceans. Given the fact that many molting-disrupting chemicals accumulate in crustacean tissues and that the effect on molting is not readily visible in the field, the disruption of molting by environmental chemicals has been dubbed the invisible endocrine disruption. In recent years, much advancement has been made in both the documentation of the phenomenon of molting disruption and the search for mechanisms, by which molting disruption occurs. This review provides an overview of the current status of the field of invisible endocrine disruption, and perspectives on future directions are also presented.

Is the development of Daphnia magna neonates affected by short-term exposure to polyethylene microplastics?

The study presents responses of D. magna newborns exposed during 96 h to polyethylene microplastics (MP) of size 40-48 μm in the concentrations of 20; 40; 80; 160 and 320 mg/L. The experimental design consisted of two exposure scenarios: the first group was fed at the beginning and after 48 h (3x10^-5 cells/mL of Raphidocelis subcaptata and fermented solution) and the second group was not fed as an additional stressor. The mobility of the organisms was not significantly affected in the presence of microplastics for both exposure groups. Nevertheless, the qualitative analysis showed that neonates promptly ingested microplastics in the first 24 h of the test, independently of the treatment. Polyethylene microplastics did not influence the molting process, however, significant differences were observed between the number of molts of the exposure without feed and with feed in 24 h (p = 0.0007), 48 h (p = 2.4 x 10^-10), 72 h (p = 3.6 x 10^-10) and 96 h (p = 0.003). The final body length of D. magna also showed that the food administration model in the tests contributes to the differentiation in responses.

Nanomaterials in the Environment Acquire an "Eco-Corona" Impacting their Toxicity to Daphnia Magna-a Call for Updating Toxicity Testing Policies

Nanomaterials (NMs) are particles with at least one dimension between 1 and 100 nm and a large surface area to volume ratio, providing them with exceptional qualities that are exploited in a variety of industrial fields. Deposition of NMs into environmental waters during or after use leads to the adsorption of an ecological (eco-) corona, whereby a layer of natural biomolecules coats the NM changing its stability, identity and ultimately toxicity. The eco-corona is not currently incorporated into ecotoxicity tests, although it has been shown to alter the interactions of NMs with organisms such as Daphnia magna (D. magna). Here, the literature on environmental biomolecule interactions with NMs is synthesized and a framework for understanding the eco-corona composition and its role in modulating NMs ecotoxicity is presented, utilizing D. magna as a model. The importance of including biomolecules as part of the current international efforts to update the standard testing protocols for NMs, is highlighted. Facilitating the formation of an eco-corona prior to NMs ecotoxicity testing will ensure that signaling pathways perturbed by the NMs are real rather than being associated with the damage arising from reactive NM surfaces "acquiring" a corona by pulling biomolecules from the organism's surface.

Effects of DEHP on post-embryonic development, nuclear receptor expression, metabolite and ecdysteroid concentrations of the moth Spodoptera littoralis

Di (2-ethylhexyl) phthalate (DEHP) is recognized in vertebrates as an Endocrine Disrupting Chemical (EDC). DEHP can alter steroid hormones production, development, reproduction and behavior in vertebrates. Only few studies investigated DEHP effects on insects. However, some recent studies on aquatic insects showed that DEHP could also act as an EDC by interfering with the signaling pathways of ecdysteroids, the main hormones involved in the control of insect post-embryonic development and physiology. The aim of the study was to investigate (1) the fate of DEHP within a terrestrial insect species by exposing larvae to food containing a wide range of DEHP concentrations and (2) the effects of this chemical on their post-embryonic development and metamorphosis, by using a multi-level approach. DEHP was shown to be present both in larvae and resulting stages, with higher concentrations in chrysalises and adults than in larvae. DEHP concentrations also decreased at the end of the last larval instar, suggesting the metabolic transformation or excretion of this chemical during this time. Only the two highest DEHP doses induced higher insect mortality, whereas low and intermediate concentrations increased larval food consumption without affecting body weight. Metabolic profiles showed that in control insects, the last three days before metamorphosis correspond to a metabolic transition, but with time-dependent changes in treated insects. Interestingly, DEHP treatments also alter both hemolymphatic ecdysteroid titers and expression levels of ecdysteroid response genes. These results confirm that DEHP can alter insect post-embryonic development and metamorphosis, by interfering with ecdysteroid pathways.

Identification of molt-inhibiting hormone and ecdysteroid receptor cDNA sequences in Gammarus pulex, and variations after endocrine disruptor exposures

In amphipods, growth, development and reproduction are mediated by the molt, which is a hormonally controlled process and which, therefore, could be impacted by endocrine disruption compounds (EDC). The molt process is controlled by both X-organ (XO) and Y-organ (YO) through a variety of hormones and receptors including the molt-inhibiting hormone (MIH) and the ecdysteroid receptor (EcR). However, although many studies were devoted to characterize MIH and EcR in crustaceans, only few works evaluated their variations under EDCs exposures. Consequently, the present work aimed to characterize MIH and EcR genes of the amphipod Gammarus pulex, as well as to study their relative expression variations after exposure to four EDCs, proved in vertebrates: ethinylestradiol (estrogen), 4-hydroxytamoxifen (anti-estrogen), 17α-methyltestosterone (androgen) and cyproterone acetate (anti-androgen). PCR amplification allowed to obtain 204 bp length and 255 bp length fragments, encoding for partial sequences of 68 amino acids and 85 amino acids, which correspond to EcR and MIH, respectively, and which are highly conserved in crustacean species. Results highlighted MIH and EcR expressions mainly in G. pulex head, which is the localization of XO and YO. Moreover, irrespective of the EDC exposure, increases of MIH and EcR relative expressions were observed, as it was observed after the exposure to 20-hydroxyecdysone (20HE), the natural molt hormone, used as positive control. Therefore, it appeared that tested EDCs behaved like 20HE, suggesting that their effects could occur through the ecdysteroids pathways, and so impact the molt process of G. pulex on the long term. Finally, the present study is a first step in the possibility of using MIH and EcR relative expressions as biomarkers of exposure for EDCs risk assessment. However additional studies must first be carried out to better characterize and understand their variations, and also better predicted consequences for the exposed amphipods.

Ecotoxicity of the nonsteroidal ecdysone mimic RH-5849 to Daphnia magna

The nonsteroidal ecdysone mimic 1,2-dibenzoyl-1-tert-butylhydrazine (RH-5849), a novel insect growth regulator, is mainly registered for use in rice fields. So far, its toxicity and ecological risks towards aquatic cladoceran invertebrates remain unclear. In this study, RH-5849 was evaluated for its acute and 21-day chronic toxicity towards Daphnia magna. The viability, morphology, growth, and reproduction of D. magna were observed to establish a concentration-toxicity relationship associated with the RH-5849 exposure. In addition, the relationship between the changes of physiological and biochemical indices and the chronic indices was analyzed in order to find potential early warning indicators in D. magna to the chronic risk of RH-5849 exposure. The results showed that the 48-h EC₅₀ of acute immobilization and EC₅₀ of 21-day survival of RH-5849 on D. magna were 45.3 and 1.34 mg/L, respectively. Chronic exposure to RH-5849 mainly affected the reproductive parameters of D. magna and the no observed effect concentration (NOEC) and the EC₅₀ were 0.050 and 0.5423 mg/L, respectively. The number of offspring per female reduced significantly after 21-day exposure to 0.10 mg/L of RH-5849. The morphological changes, manifested in head width and body length, the length of the helmet or apical spine, and the curvature and transparency of the body, were observed in RH-5849-treated groups. Moreover, it was found that the alkaline phosphatase activity in D. magna after 5-7-day exposure was positively correlated with the number of offspring per female after 21 days. These results indicate the potential risk of RH-5849 towards aquatic crustaceans should be taken into consideration when applied to rice fields.

Impaired reproduction and individual growth of the water flea Daphnia magna as consequence of exposure to the non-ester pyrethroid etofenprox

The effect of the pesticide etofenprox (0.76, 0.95, 1.18, 1.48, and 1.85 μg L^-1) on survival, reproduction, and growth of Daphnia magna organisms was monitored using 21-day exposure tests. In order to test pesticide effects on D. magna, survival, length, mean total neonates per female, mean brood size, time to first reproduction, mean number broods per female, cumulative molting, and the population parameter intrinsic rate of natural increase (r) were used. Reproduction was seriously affected by etofenprox. Concentrations of etofenprox higher than 1.18 μg L^-1affected all the reproductive parameters analyzed as well as individual length. However, daphnids' survival after 21 days of pesticide exposure did not exhibited differences among experimental and control groups. The no observed effect concentration (NOEC), the lowest observed effect concentration (LOEC), and the maximum acceptable toxicant concentration (MATC) were calculated for the different parameters. A MATC estimation of 1.32 μg L^-1 was calculated for mean brood size, mean number of broods per female, mean number of neonates per female, and the intrinsic rate of growth population. Etofenprox effect on the algae Nannochloris oculata was also evaluated. The selected etofenprox concentrations did not affect algal growth rate (μ) after 24 h; however, N. oculata exposed during 48 and 72 h to the highest etofenprox concentration showed a decreased in its population rate.

Effects of contaminants of emerging concern on Myzus persicae (Sulzer, Hemiptera: Aphididae) biology and on their host plant, Capsicum annuum

Many countries are utilizing reclaimed wastewater for agriculture as water demands due to drought, rising temperatures, and expanding human populations. Unfortunately, wastewater often contains biologically active, pseudopersistant pharmaceuticals, even after treatment. Runoff from agriculture and effluent from wastewater treatment plants also contribute high concentrations of pharmaceuticals to the environment. This study assessed the effects of common pharmaceuticals on an agricultural pest, the aphid Myzus persicae (Sulzer, Hemiptera: Aphididae). Second instar nymphs were transferred to bell peppers (Capsicum annuum) that were grown hydroponically. Treatment plants were spiked with contaminants of emerging concern (CECs) at environmentally relevant concentrations found in reclaimed wastewater. M. persicae displayed no differences in population growth or microbial community differences due to chemical treatments. Plants, however, displayed significant growth reduction in antibiotic and mixture treatments, specifically in wet root masses. Antibiotic treatment masses were significantly reduced in the total and root wet masses. Mixture treatments displayed an overall reduction in plant root wet mass. Our results suggest that the use of reclaimed wastewater for crop irrigation would not affect aphid populations, but could hinder or delay crop production.

Testing lagoonal sediments with early life stages of the copepod Acartia tonsa (Dana): An approach to assess sediment toxicity in the Venice Lagoon

The early-life stages of development of the calanoid copepod Acartia tonsa from egg to copepodite I is proposed as an endpoint for assessing sediment toxicity by exposing newly released eggs directly onto the sediment-water interface. A preliminary study of 5 sediment samples collected in the lagoon of Venice highlighted that the larval development rate (LDR) and the early-life stages (ELS) mortality endpoints with A. tonsa are more sensitive than the standard amphipod mortality test; moreover LDR resulted in a more reliable endpoint than ELS mortality, due to the interference of the sediment with the recovery of unhatched eggs and dead larvae. The LDR data collected in a definitive study of 48 sediment samples from the Venice Lagoon has been analysed together with the preliminary data to evaluate the statistical performances of the bioassay (among replicate variance and minimum significant difference between samples and control) and to investigate the possible correlation with sediment chemistry and physical properties. The results showed that statistical performances of the LDR test with A. tonsa correspond with the outcomes of other tests applied to the sediment-water interface (Strongylocentrotus purpuratus embryotoxicity test), sediments (Neanthes arenaceodentata survival and growth test) and porewater (S. purpuratus); the LDR endpoint did, however, show a slightly higher variance as compared with other tests used in the Lagoon of Venice, such as 10-d amphipod lethality test and larval development with sea urchin and bivalves embryos. Sediment toxicity data highlighted the high sensitivity and the clear ability of the larval development to discriminate among sediments characterized by different levels of contamination. The data of the definitive study evidenced that inhibition of the larval development was not affected by grain-size and the organic carbon content of the sediment; in contrast, a strong correlation between inhibition of the larval development and the sediment concentrations of some metals (Cu, Hg, Pb, Zn), acid-volatile sulphides (AVS), polychlorinated biphenyls (PCBs) and polynuclear aromatic hydrocarbons (PAHs) was found. No correlation was found with DDTs, hexachlorobenzene and organotin compounds.

Contaminants of emerging concern affect Trichoplusia ni growth and development on artificial diets and a key host plant

Many countries are utilizing reclaimed wastewater for agriculture because drought, rising temperatures, and expanding human populations are increasing water demands. Unfortunately, wastewater often contains biologically active, pseudopersistent pharmaceuticals, even after treatment. Runoff from farms and output from wastewater treatment plants also contribute high concentrations of pharmaceuticals to the environment. This study assessed the effects of common pharmaceuticals on an agricultural pest, Trichoplusia ni (Lepidoptera: Noctuidae). Larvae were reared on artificial diets spiked with contaminants of emerging concern (CECs) at environmentally relevant concentrations. Trichoplusia ni showed increased developmental time and mortality when reared on artificial diets containing antibiotics, hormones, or a mixture of contaminants. Mortality was also increased when T. ni were reared on tomatoes grown hydroponically with the same concentrations of antibiotics. The antibiotic-treated plants translocated ciprofloxacin through their tissues to roots, shoots, and leaves. Microbial communities of T. ni changed substantially between developmental stages and when exposed to CECs in their diets. Our results suggest that use of reclaimed wastewater for irrigation of crops can affect the developmental biology and microbial communities of an insect of agricultural importance.

Effects of contaminants of emerging concern on Megaselia scalaris (Lowe, Diptera: Phoridae) and its microbial community

Drought, rising temperatures, and expanding human populations are increasing water demands. Many countries are extending potable water supplies by irrigating crops with wastewater. Unfortunately, wastewater contains biologically active, long-lived pharmaceuticals, even after treatment. Run-off from farms and wastewater treatment plant overflows contribute high concentrations of pharmaceuticals to the environment. This study assessed the effects of common pharmaceuticals on a cosmopolitan saprophagous insect, Megaselia scalaris (Diptera: Phoridae). Larvae were reared on artificial diets spiked with contaminants of emerging concern (CECs) at environmentally relevant concentrations. Female flies showed no oviposition preference for treated or untreated diets. Larvae exposed to caffeine in diets showed increased mortality, and larvae fed antibiotics and hormones showed signs of slowed development, especially in females. The normal sex ratio observed in M. scalaris from control diets was affected by exposure to caffeine and pharmaceutical mixture treatments. There was an overall effect of treatment on the flies' microbial communities; notably, caffeine fed insects displayed higher microbial variability. Eight bacterial families accounted for approximately 95% of the total microbes in diet and insects. Our results suggest that CECs at environmentally relevant concentrations can affect the biology and microbial communities of an insect of ecological and medical importance.

Toxic and endocrine disrupting effects of wastewater treatment plant influents and effluents on a freshwater isopod Asellus aquaticus (Isopoda, Crustacea)

In the present study a biological "in vivo" assay, with freshwater isopod Asellus aquaticus, was used to define and evaluate the potential impact of the wastewater treatment plant (WWTP) wastewaters on local wildlife. Samples of both untreated and mechanically and biologically treated WWTP wastewater, were tested in the presence and absence of the formulated sediment for their lethal and sublethal effects. Chronic exposures to wastewater samples caused concentration dependent reduced locomotion, body pigmentation and molting frequency in exposed organisms. The observed effects indicate the overall toxicity and endocrine disruption of the wastewater samples. In contrast stimulations of the feeding rate and growth rate of the test organisms during the chronic exposure to sublethal levels of wastewater samples were observed, indicating an improvement in nutritional quality of the wastewater. The most sensitive exposure endpoint was molting frequency of tested organisms, which indicated the presence of estrogenically active endocrine disrupting compounds (EDCs). Raw wastewater caused up to 42% molting frequency reduction of exposed A. aquaticus when exposed to five times diluted untreated wastewater sample, while undiluted treated wastewater caused a 61% molting frequency reduction. The presence of estrogenically active compounds in the wastewater was confirmed with the yeast estrogen screen assay (YES test), which assigned the highest estrogenic activity to a mechanically and biologically treated wastewater sample, and lower estrogenic activity to all other tested samples. The importance of presence of the formulated sediment was determined, as it lessened the effects of all WWTP wastewater samples in all observed exposures.

Transcriptomic, cellular and life-history responses of Daphnia magna chronically exposed to benzotriazoles: Endocrine-disrupting potential and molting effects

Benzotriazoles (BZTs) are ubiquitous aquatic contaminants used in a wide range of industrial and domestic applications from aircraft deicers to dishwasher tablets. Acute toxicity has been reported in aquatic organisms for some of the BZTs but their mode of action remains unknown. The objectives of this study were to evaluate the transcriptomic response of D. magna exposed to sublethal doses of 1H-benzotriazole (BTR), 5-methyl-1H-benzotriazole (5MeBTR) and 5-chloro-1H-benzotriazole (5ClBTR) using RNA-sequencing and quantitative real-time PCR. Cellular and life-history endpoints (survival, number of neonates, growth) were also investigated. Significant effects on the molting frequency were observed after 21-d exposure to 5MeBTR and 5ClBTR. No effects on molting frequency were observed for BTR but RNA-seq results indicated that this BZT induced the up-regulation of genes coding for cuticular proteins, which could have compensated the molting disruption. Molting in cladocerans is actively controlled by ecdysteroid hormones. Complementary short-term temporal analysis (4- and 8-d exposure) of the transcription of genes related to molting and hormone-mediated processes indicated that the three compounds had specific modes of action. BTR induced the transcription of genes involved in 20-hydroxyecdysone synthesis, which suggests pro-ecdysteroid properties. 5ClBTR exposure induced protein activity and transcriptional levels of chitinase enzymes, associated with an impact on ecdysteroid signaling pathways, which could explain the decrease in molt frequency. Finally, 5MeBTR seemed to increase molt frequency through epigenetic processes. Overall, results suggested that molting effects observed at the physiological level could be linked to endocrine regulation impacts of BZTs at the molecular level.

Ecdysone receptor (EcR) and ultraspiracle (USP) genes from the cyclopoid copepod Paracyclopina nana: Identification and expression in response to water accommodated fractions (WAFs)

Ecdysteroid hormones are pivotal in the development, growth, and molting of arthropods, and the hormone pathway is triggered by binding ecdysteroid to a heterodimer of the two nuclear receptors; ecdysone receptors (EcR) and ultraspiracle (USP). We have characterized EcR and USP genes, and their 5'-untranslated region (5'-UTR) from the copepod Paracyclopina nana, and studied mRNA transcription levels in post-embryonic stages and in response to water accommodated fractions (WAFs) of crude oil. The open reading frames (ORF) of EcR and USP were 1470 and 1287bp that encoded 490 and 429 amino acids with molecular weight of 121.18 and 105.03kDa, respectively. Also, a well conserved DNA-binding domain (DBD) and ligand-binding domain (LBD) were identified which confirmed by phylogenetic analysis. Messenger RNA transcriptional levels of EcR and USP were developmental stage-specific in early post-embryonic stages (N3-4). However, an evoked expression of USP was observed throughout copepodid stage and in adult females. WAFs (40 and 80%) were acted as an ecdysone agonist in P. nana, and elicited the mRNA transcription levels in adults. Developmental stage-specific transcriptional activation of EcR and USP in response to WAFs was observed. USP gene was down-regulated in the nauplius in response to WAF, whereas up-regulation of USP was observed in the adults. This study represents the first data of molecular elucidation of EcR and USP genes and their regulatory elements from P. nana and the developmental stage specific expression in response to WAFs, which can be used as potential biomarkers for environmental stressors with ecotoxicological evaluations in copepods.

Dieldrin reduces male production and sex ratio in Daphnia galeata mendotae

We used the sex ratio of neonate Daphnia, as well as the more standard endpoints of adult survivorship and fecundity and neonatal morphology, as an assay for detecting the effects of the insecticides endosulfan and dieldrin. Dieldrin caused a decrease in sex ratio (number of males/number of males plus females); we observed no endosulfan effect. We estimated (by extrapolation) that the sex ratio was reduced by dieldrin from concentrations of about 30 ppb and higher, based on a linear decrease in sex ratio with log dieldrin concentrations from 50 to 600 ppb. Neither insecticide significantly affected adult survival or clutch size. Because sex ratio changed but total neonate production did not change, the data suggest that the effect of dieldrin was on the sex-determining system during embryogenesis. Neither insecticide caused morphological abnormalities. Mixtures of the two pesticides produced only additive effects.

Relating suborganismal processes to ecotoxicological and population level endpoints using a bioenergetic model

Ecological effects of environmental stressors are commonly evaluated using organismal or suborganismal data, such as standardized toxicity tests that characterize responses of individuals (e.g., mortality and reproduction) and a rapidly growing body of "omics" data. A key challenge for environmental risk assessment is relating such information to population dynamics. One approach uses dynamic energy budget (DEB) models that relate growth and reproduction of individuals to underlying flows of energy and elemental matter. We hypothesize that suborganismal information identifies DEB parameters that are most likely impacted by a particular stressor and that the DEB model can then project suborganismal effects on life history and population endpoints. We formulate and parameterize a model of growth and reproduction for the water flea Daphnia magna. Our model resembles previous generic bioenergetic models, but has explicit representation of discrete molts, an important feature of Daphnia life history. We test its ability to predict six endpoints commonly used in chronic toxicity studies in specified food environments. With just one adjustable parameter, the model successfully predicts growth and reproduction of individuals from a wide array of experiments performed in multiple laboratories using different clones of D. magna raised on different food sources. Fecundity is the most sensitive endpoint, and there is broad correlation between the sensitivities of fecundity and long-run growth rate, as is desirable for the default metric used in chronic toxicity tests. Under some assumptions, we can combine our DEB model with the Euler-Lotka equation to estimate longrun population growth rates at different food levels. A review of Daphnia gene-expression experiments on the effects of contaminant exposure reveals several connections to model parameters, in particular a general trend of increased transcript expression of genes involved in energy assimilation and utilization at concentrations affecting growth and reproduction. The sensitivity of fecundity to many model parameters was consistent with frequent generalized observations of decreased expression of genes involved in reproductive physiology, but interpretation of these observations requires further mechanistic modeling. We thus propose an approach based on generic DEB models incorporating few essential species-specific features for rapid extrapolation of ecotoxicogenomic assays for Daphnia-based population risk assessment.

Pharmaceuticals and personal care products alter the holobiome and development of a medically important mosquito

The increasing demand for fresh water has forced many countries to use reclaimed wastewater for agricultural purposes. This water contains pharmaceuticals and personal care products (PPCPs) that remain biologically active following passage through wastewater treatment plants. Run-off from farms and contaminated water from treatment facilities exposes aquatic ecosystems to PPCPs. This study examined the effects of PPCPs on a lower trophic organism. Culex quinquefasciatus larvae were reared in water contaminated with environmentally relevant concentrations of common PPCPs. Acetaminophen alone and a mixture of contaminants were found to increase developmental time of larvae. Susceptibility to Bti increased in larvae exposed to antibiotics, acetaminophen, or a mixture of PPCPs. Antibiotics, hormones, and the mixture altered the mosquito bacterial microbiome. Overall, the results indicate that at environmentally relevant concentrations, PPCPs in reclaimed water can have biologically important effects on an ecologically and medically important lower trophic level insect.

Adverse effects of bisphenol A on water louse (Asellus aquaticus)

Experiments were performed to study the effects of short and long-term exposure to bisphenol A (BPA) on a freshwater crustacean isopod Asellus aquaticus (L.). Two life stages of isopods were exposed to a range of BPA concentrations, from aqueous and two dietary sources, in the form of with BPA spiked conditioned alder leaf (Alnus glutinosa) discs, or spiked formulated sediment, to determine the relative importance of each source of exposure on the uptake of this contaminant. Several lethal and sublethal endpoints were evaluated in this study to measure the potential effects of BPA on A. aquaticus, including mortality, growth and feeding rate inhibition, mobility inhibition, de-pigmentation and molting disturbances. They signify a correlation to BPA levels and a difference in BPA uptake efficiency from different uptake sources. Results of acute exposure to BPA show a greater sensitivity of test systems using juvenile specimens with a 96 h LC₅₀ of 8.6 mg L(-1) BPA in water medium and a 96 h LC₅₀ of 13.5 mg L(-1) BPA in sediment. In comparison, adult isopods show a 96 h LC₅₀ of 25.1 mg L(-1) BPA in water medium and a 96 h LC₅₀ of 65.1 mg L(-1) BPA in sediment. Observed endpoints of chronic exposures suggest the alder leave discs to be the most efficient uptake source of BPA, in contrast to uptake from water or heterogeneous sediment. Significant (p<0.05) growth inhibition, with a 21d NOEC of 0.5/2.5 mg L(-1) (for juvenile/adult organisms), and feeding rate inhibition, with a 21d NOEC of 0.5/1.0 mg L(-1) (for juvenile/adult organisms), were proven to be the most sensitive toxicity endpoints. An even more sensitive effect turned out to be molting frequency, which was significantly reduced; a 21d NOEC was 1.0 mg L(-1) of BPA for adult organisms and an even lower 21d NOEC of 0.05 mg L(-1) of BPA for juveniles. The observed endpoints are recorded at very low, non-toxic exposure concentrations, indicating that BPA acts as an endocrine disrupting compound, as well as a toxic substance. We also determined the importance of the direct dietary uptake of the pollutants, significant for juveniles as well as adult animals.

Toxicity of sediment-bound pollutants in the Seine estuary, France, using a Eurytemora affinis larval bioassay

Coastal urbanisation exposes surrounding estuarine environments to urban-related contaminants such as polycyclic aromatic hydrocarbons (PAHs), polychlorobiphenyls (PCBs) and pesticide mixtures. Hydrophobic contaminants can adsorb on estuarine sediments. They can subsequently be released on a massive scale in the aquatic environment due to artificial or natural phenomena (e.g. dredging, tides), thereby threatening living organisms. The contamination of sediment is a significant ecological issue in the Seine estuary, France. However, few relevant methods have been developed to assess sediment toxicity and its ecological impacts in a cost-effective way. In this context, we aimed to assess the toxicity of natural sediments from the Seine estuary on the development of the calanoid copepod Eurytemora affinis using a previously developed larval bioassay. This assay involves direct exposure of nauplii to elutriates of sediments for six days. Sediments were collected along the Seine estuary from six polluted sites and one reference site. Pollutants in this estuary included PAHs, PCBs and OCPs (organochlorine pesticides). Nauplius survival was significantly more affected by exposure to all contaminated sediment elutriates, than by exposure to sediment from Yville-sur-Seine (the reference site), whereas nauplius growth was significantly reduced after exposure to contaminated sediment elutriates from four of the six contaminated sites. We identified two distinct site clusters, one including both the sand-rich and the least polluted sediments (Oissel, Quillebeuf-sur-Seine, Caudebec-en-Caux) and the other including both the clay- and silt-rich, and the most polluted sediments (La Bouille, Poses, Pont de Normandie). As expected, survival was significantly more impacted after exposure to elutriates from the second cluster than from the first. This work enables (i) assessment of the toxicity of natural sediments in the Seine estuary and (ii) validation of the larval bioassay previously developed using sorbed sediment with model molecules.

Cadmium inhibits molting of the freshwater crab Sinopotamon henanense by reducing the hemolymph ecdysteroid content and the activities of chitinase and N-acetyl-β-glucosaminidase in the epidermis

Molting is an essential process during the growth of crustaceans, which is coordinated by ecdysteroids secreted by the Y-organ, molting inhibiting hormone secreted by the X-organ sinus-gland complex, as well as chitinase and N-acetyl-β-glucosaminidase synthesized by the epidermis. Cadmium is one of the toxic metals in the aquatic environment. However, the endocrine effects of cadmium on the molting of freshwater crabs and the underlying mechanisms are unknown. To investigate these, freshwater crabs (Sinopotamon henanense) were acutely exposed to 0, 7.25, 14.5 and 29 mg/l Cd for 3, 4, 5 days or in some experiments for 4 days after eyestalk-ablation. The concentration of hemolymph ecdysone and the activities of the molting enzymes chitinase and NAG were measured. Histological changes in the epidermal tissues were documented. Our results showed that eyestalk ablation increased the ecdysteroid content as well as the activities of chitinase and NAG, which were inhibited by cadmium in a concentration-dependent manner; histological examinations demonstrated that eyestalk ablation produced storage particles in the epidermal tissues, which was also reduced by cadmium in a concentration-dependent manner. Our data suggest that cadmium disrupts endocrine function through inhibiting the secretion of ecdysteroids by the Y-organ and altering with the regulation of chitinase and NAG activity in the epidermis. This work provides new insights into the mechanisms underlying the molting inhibition effect of cadmium on the crabs.

Validation and extension of a similarity-based approach for prediction of acute aquatic toxicity towards Daphnia magna

Quantitative structure-activity relationship (QSAR) models for predicting acute toxicity to Daphnia magna are often associated with poor performances, urging the need for improvement to meet REACH requirements. The aim of this study was to evaluate the accuracy, stability and reliability of a previously published QSAR model by means of further external validation and to optimize its performance by means of extension to new data as well as a consensus approach. The previously published model was validated with a large set of new molecules and then compared with ChemProp model, from which most of the validation data were taken. Results showed better performance of the proposed model in terms of accuracy and percentage of molecules outside the applicability domain. The model was re-calibrated on all the available data to confirm the efficacy of the similarity-based approach. The extended dataset was also used to develop a novel model based on the same similarity approach but using binary fingerprints to describe the chemical structures. The fingerprint-based model gave lower regression statistics, but also less unpredicted compounds. Eventually, consensus modelling was successfully used to enhance the accuracy of the predictions and to halve the percentage of molecules outside the applicability domain.

Direct and indirect responses of a freshwater food web to a potent synthetic oestrogen

Endocrine-disrupting chemicals (EDCs) in municipal effluents directly affect the sexual development and reproductive success of fishes, but indirect effects on invertebrate prey or fish predators through reduced predation or prey availability, respectively, are unknown. At the Experimental Lakes Area in northwestern Ontario, Canada, a long-term, whole-lake experiment was conducted using a before-after-control-impact design to determine both direct and indirect effects of the synthetic oestrogen used in the birth control pill, 17α-ethynyloestradiol (EE2). Algal, microbial, zooplankton and benthic invertebrate communities showed no declines in abundance during three summers of EE2 additions (5-6 ng l(-1)), indicating no direct toxic effects. Recruitment of fathead minnow (Pimephales promelas) failed, leading to a near-extirpation of this species both 2 years during (young-of-year, YOY) and 2 years following (adults and YOY) EE2 additions. Body condition of male lake trout (Salvelinus namaycush) and male and female white sucker (Catostomus commersonii) declined before changes in prey abundance, suggesting direct effects of EE2 on this endpoint. Evidence of indirect effects of EE2 was also observed. Increases in zooplankton, Chaoborus, and emerging insects were observed after 2 or 3 years of EE2 additions, strongly suggesting indirect effects mediated through the reduced abundance of several small-bodied fishes. Biomass of top predator lake trout declined by 23-42% during and after EE2 additions, most probably an indirect effect from the loss of its prey species, the fathead minnow and slimy sculpin (Cottus cognatus). Our results demonstrate that small-scale studies focusing solely on direct effects are likely to underestimate the true environmental impacts of oestrogens in municipal wastewaters and provide further evidence of the value of whole-ecosystem experiments for understanding indirect effects of EDCs and other aquatic stressors.

Sublethal toxic effects of nonylphenol ethoxylate and nonylphenol to Moina macrocopa

The aim of this paper was to examine the sublethal toxic effects of nonylphenol ethoxylate (NP10EO), its primary degradation product nonylphenol (NP), and their mixture on Moina macrocopa. Chronic toxicity tests were carried out by using sublethal chemical concentrations. Results showed that all treatments reduced the survivorship, body length, and reproduction of M. macrocopa with NP being 10 %-20 % more toxic to M. macrocopa than NP10EO. Results also indicated that the toxic effects of NP10EO and NP mixture on M. macrocopa were more severe than that of any single chemical alone. At the highest concentration in this experiment, 0.337 mg L(-1) NP10EO plus 0.0154 mg L(-1) NP treatment caused the survivorship of M. macrocopa to zero, neonates number of reproductions to zero, 45.5 % reduction in the body length, and 88 % reduction in the total neonates number.

Development of a larval bioassay using the calanoid copepod, Eurytemora affinis to assess the toxicity of sediment-bound pollutants

Hydrophobic pollutants, in particular sediment-sorbed organic compounds, are widespread in the aquatic environment and could represent a threat to living organisms. Estuarine species, which live in turbulent ecosystems, are particularly exposed to this mode of contamination. For precise evaluation of the toxicity of hydrophobic contaminants desorbed from particles, a new larval assay using nauplii of the estuarine calanoid copepod Eurytemora affinis was developed. It consists of the direct exposure of copepods during naupliar development to elutriates of an unpolluted sediment spiked with different model contaminants. This bioassay measures the toxicity of the bioavailable fraction of particle-sorbed pollutants on the naupliar stage of copepods. Mortality and growth (non-invasive endpoints) in nauplii were analysed after six days of exposure. This approach was validated using six pollutants with different modes of action: benzo[a]pyrene (BaP), dimethylbenzo[a]anthracene (DMBA), phenanthrene (PHE), polychlorinated biphenyls (PCB 126, PCB 153) and 4-nonylphenol (4-NP). All these compounds induced a dose-dependent increase in toxic effects. Lethal effects only occurred at the highest tested concentrations: 58,541 and 6092 ng g(-1) dry weight sediment (dws), for PHE and DMBA, respectively. Sublethal effects (growth inhibition) were observed at lower concentrations for all tested compounds except PCB 153, from 8, 142, 297, 6092 and 8453 ng g(-1) dws for PCB 126, BaP, PHE, DMBA and 4-NP, respectively.

Effects of methyltestosterone, letrozole, triphenyltin and fenarimol on histology of reproductive organs of the copepod Acartia tonsa

The marine calanoid copepod Acartia tonsa was exposed to methyltestosterone (MET, 1.6-126 μg L(-1)), letrozole (LET, 10-1000 μg L(-1)), triphenyltin chloride (TPT, 0.0014-0.0088 μg L(-1) TPT-Sn) and fenarimol (FEN, 2.8-105 μg L(-1)) for 21 d covering a full life-cycle. All four compounds investigated are known to act as androgens in vertebrates. The digestive tract, musculature, nervous system, reproductive organs, gonad and accessory sexual glands were examined by light microscopy after routine staining and immune-labelling for detection of apoptosis and determination of proliferation activities. MET induced an inhibition of oogenesis, oocyte maturation and yolk formation, respectively, which was most pronounced at the lowest concentrations tested. In LET exposed males, spermatogenesis was enhanced with very prominent gamete stages; in some stages apoptosis occurred. The spermatophore was hypertrophied and displayed deformations. In females, LET induced a disorder of oogenesis and disturbances in yolk synthesis. TPT stimulated the male reproductive system at 0.0014 and 0.0035 μg TPT-SnL(-1), whereas inhibiting effects were observed in the female gonad at 0.0088 μg TPT-SnL(-1). In FEN exposed females proliferation of gametes was reduced and yolk formation showed irregular features at 2.8-105 μgL(-1). In FEN exposed males an elevated proliferation activity was observed. No pathological alterations in other organ systems, e.g. the digestive tract including the hindgut acting as respiratory organ, the nervous system, or the musculature were seen. This indicates that the effects on gonads might be caused rather by disturbance of endocrine signalling or interference with hormone metabolism than by general toxicity.

Polybrominated diphenyl ethers disrupt molting in neonatal Daphnia magna

Polybrominated diphenyl ethers (PBDEs) are flame-retardants which can bioaccumulate and biomagnify and are found worldwide despite their banned usage in some countries. In recent years, the possibility that PBDEs may disrupt endocrine functions in vertebrates has been well investigated, but little attention has been paid to the endocrine disrupting potential in aquatic invertebrates. The current study aimed to investigate whether PBDEs affect molting in neonatal Daphnia magna. Prior to molting studies, 48 h LC50 values were tested for several environmentally prevalent PBDEs: PBDEs-28, -47, -99, -100 and -209. The 48 h LC50s determined were 110.7, 7.9, 2.6, and 11.1 μg/L for PBDEs-28, -47, -99, and -100, respectively, but the highest concentration of PBDEs-209 tested (2.5 mg/L) did not affect survival at 48 h. Sublethal concentrations of these were used to investigate their potential effects on molting, assessed by the time taken to reach 4 molts. Molting studies found that PBDE-28 at 12 μg/L significantly increased the time it took to complete 4 molts. PBDE-47 at 20 μg/L inhibited daphnid molting initially but such an inhibitory effect disappeared with the prolongation of exposure due to the death of sensitive individuals. No other PBDEs affected molting at the concentrations tested, while still maintaining relatively high survival rates. In conclusion, this study found that PBDEs-28 and -47 can delay molting at μg/L concentrations, which raises concern for disrupted molting in crustaceans exposed to PBDEs.

Effects of endosulfan exposure and Taura Syndrome Virus infection on the survival and molting of the marine penaeid shrimp, Litopenaeus vannamei

Molting in crustaceans is an important endocrine-controlled biological process that plays a critical role in growth and reproduction. Many factors can affect this physiological cycle in crustaceans including environmental stressors and disease agents. For example the pathology of Taura Syndrome Virus (TSV) of shrimp is closely related to molting cycle. Similarly, endosulfan, a commonly used pesticide is a potential endocrine disruptor. This study explores interrelationships between pesticide exposure, virus infection and their interactions with physiology and susceptibility of the shrimp. Litopenaeus vannamei (Pacific white shrimp) were challenged with increasing doses of endosulfan and TSV (TSV-C, a Belize reference strain) to determine the respective median lethal concentrations (LC(50)s). The 96-h endosulfan LC(50) was 5.32 μg L(-1), while the 7-d TSV LC(50) was 54.74 mg L(-1). Subsequently, based on their respective LC(50) values, a 20-d interaction experiment with sublethal concentrations of endosulfan (2 μg L(-1)) and TSV (30 mg L(-1)) confirmed a significant interaction (p<0.05, χ(2)=5.29), and thereby the susceptibility of the shrimp. Concurrently, molt-stage of animals, both at the time of exposure and death, was compared with mortality. For animals challenged with TSV, no strong correlation between molt-stage and mortality was observed (p>0.05). For animals exposed to endosulfan, animals in the postmolt stage were shown to be more susceptible to acute toxicity (p<0.05). For animals exposed to both TSV and endosulfan, interference of endosulfan-associated stress lead to increasingly higher susceptibility at postmolt (p<0.05) during the acute phase of the TSV disease cycle.

Acute and chronic toxicity of polychlorinated biphenyl 126 to Tigriopus japonicus: effects on survival, growth, reproduction, and intrinsic rate of population growth

The harpacticoid copepod Tigriopus japonicus has a wide geographical distribution and is considered as a suitable model species for the assessment of toxicity of marine pollutants. The aim of the present study was to test the impacts of polychlorinated biphenyl (PCB) 126 (3,3',4,4',5-pentachlorobiphenyl) on the growth, development, and reproduction of T. japonicus in two successive generations. We first quantified the 96-h 50% lethal concentration (2.83 mg/L; all reported concentrations are nominal values), the no-observed-effect concentration (0.6 mg/L), and the lowest-observed-effect concentration (LOEC; 1.2 mg/L) of PCB126 in the nauplii. Nauplii were more sensitive than the adults, which still survived at the highest tested PCB126 concentration (8 mg/L). In the chronic toxicity testing, 10 life history traits were quantified for T. japonicus. No obvious effect on any of these traits was observed in the first generation (F0) at tested concentrations (<100 µg/L) lower than the LOEC. During the second generational life-cycle exposure (F1), however, PCB126 had an obvious toxic effect on the reproduction (>1 µg/L) and growth (>0.1 µg/L). Thus, copepods became more sensitive to PCB126 exposure as generations developed. Among the different traits tested, body size was the most sensitive parameter. Reproduction (fecundity, number of clutches, nauplii/clutch) and intrinsic population growth were also significantly impacted by PCB exposure. The survivorship, sex ratio, hatching time, and development were not affected. Environmental risk assessment of contaminants must therefore be based on a long-term multigenerational exposure to provide a realistic measurement of the influences of pollutants on aquatic life.

Modulation in the mRNA expression of ecdysone receptor gene in aquatic midge, Chironomus riparius upon exposure to nonylphenol and silver nanoparticles

Chironomus riparius, a non-biting midge (Chironomidae, Diptera), is extensively used as a model organism in aquatic ecotoxicological studies, although little is known about its genome sequences. Ecdysteroids are steroid hormones that play an important role in development, growth, moulting of larva, and reproduction in Chironomus spp. The effect of ecdysteroids is mediated by their binding to the ecdysteroid receptor (EcR). To study the effect of environmental stressors, nonylphenol and silver nanoparticles (AgNPs), on the modulation of EcR mRNA, in this study, full length cDNA of C. riparius ecdysone receptor (CrEcR) was identified from the Expressed Sequence Tags (ESTs) database and expression of the corresponding mRNA was analyzed following exposure to nonylphenol and AgNPs. The CrEcR cDNA was 2548 base pairs (bp) in length, with a 5' untranslated region (UTR) of 242 bp and a 3' UTR of 684 bp. The open reading frame contains 1617 nucleotides, encoding 539 amino acids with a predicted molecular weight of 61 kDa and pI of 5.89, and revealed the presence of several domains associated with DNA binding, dimerization, ligand binding and transcriptional activation characteristic of steroid receptor family members. It was found that the expression level of CrEcR was significantly up-regulated on exposure to nonylphenol and significant up or down regulation was observed on exposure to AgNPs. These finding shows that nonylphenol as well as AgNPs could modulate the ecdysone nuclear receptor and may have significant implications in different developmental stages in C. riparius.

Ecdysteroid receptor from the American lobster Homarus americanus: EcR/RXR isoform cloning and ligand-binding properties

In arthropods, ecdysteroids regulate molting by activating a heterodimer formed by the ecdysone receptor (EcR) and retinoid X receptor (RXR). While this mechanism is similar in insects and crustaceans, variation in receptor splicing, dimerization and ligand affinity adds specificity to molting processes. This study reports the EcR and RXR sequences from American lobster, a commercially and ecologically important crustacean. We cloned two EcR splice variants, both of which specifically bind ponasterone A, and two RXR variants, both of which enhance binding of ponasterone A to the EcR. Lobster EcR has high affinity for ponasterone A and muristerone and moderately high affinity for the insecticide tebufenozide. Bisphenol A, diethyl phthalate, and two polychlorinated biphenyls (PCB 29 and PCB 30), environmental chemicals shown to interfere with crustacean molting, showed little or no affinity for lobster EcR. These studies establish the molecular basis for investigation of lobster ecdysteroid signaling and signal disruption by environmental chemicals.

Daphnia response to biotic stress is modified by PCBs

The aim of this study was to examine the influence of xenobiotics (PCBs) on the responses of Daphnia to biotic factors such as the presence of a predator (fish kairomone) or filamentous cyanobacteria. Both behaviour (depth selection) and life history (body size at first reproduction and fecundity) were affected by these stressors. Though there was no direct effect of PCBs, their influence resulted in disruption of the "natural" reaction to the presence of fish or cyanobacteria, leading to inadequate responses of Daphnia to these biotic threats. Examined clones of Daphnia showed significant diversity in their reaction to these stress factors, which was greater than that between Daphnia clones exposed to different environmental conditions. PCB pollution may change the frequency of Daphnia clones in favour of those whose responses to biotic stress are similar in both the absence and presence of these toxic chemicals.

Cloning and expression of ecdysone receptor (EcR) from the intertidal copepod, Tigriopus japonicus

Ecdysteroids are steroid hormones that play an important role in development, growth, molting of larva, and reproduction in the Arthropoda. The effect of ecdysteroids is mediated by its binding to ecdysteroid receptor (EcR). To investigate the role of EcR during development and the effect to environmental stressors on EcR expression in a copepod, we isolated and characterized cDNA and 5'-promoter region of the Tigriopus japonicus EcR (TJ-EcR), and studied mRNA expression pattern. The full-length TJ-EcR cDNA sequence was 1962bp in length and the open reading frame encoded 546 amino acids. The deduced TJ-EcR protein contained well-conserved DNA-binding domain and ligand-binding domain. Phylogenetic analysis revealed that TJ-EcR was clustered with the EcR of other crustaceans. TJ-EcR mRNA was expressed in a developmental stage-specific manner: high in early developmental stages and low in the adult stage. Significantly elevated expression of the TJ-EcR gene in adults was detected at hypersalinity (42ppt) and high temperature (35 degrees C) condition. The 5'-flanking region of TJ-EcR gene contains heat shock protein 70 response elements, implying that the environmental stressors may affect its expression via the stress-sensor. In addition, bisphenol A (100microg/L) repressed TJ-EcR expression. Our results suggest that TJ-EcR could be a biomarker for the monitoring of the impact of environmental stressors in copepods.

Impacts of molt-inhibiting organochlorine compounds on epidermal ecdysteroid signaling in the fiddler crab, Uca pugilator, in vitro

Because of their chemical stability and lipophilicity, many organochlorine compounds (OCs) can readily accumulate in fatty tissues of crustaceans. Several OCs have been reported to inhibit crustacean molting. To determine whether the disruption of crustacean molting by these OCs involves interference with ecdysteroid signaling in the epidermis, the impacts of five molt-inhibiting OCs on the level of N-acetyl-beta-glucosaminidase (NAG, EC 3.2.1.30) mRNA in cultured epidermal tissues from the fiddler crab, Uca pugilator, were investigated using quantitative real-time PCR. The NAG mRNA was found to be inducible by 20-hydroxyecdysone (20-HE) in cultured epidermal tissues. The inducibility of NAG mRNA in cultured epidermal tissues by 20-HE is not only further direct evidence that epidermal expression of NAG gene in U. pugilator is controlled by the molting hormone but also validates the use of the NAG mRNA as a biomarker for epidermal ecdysteroid signaling. When Aroclor 1242, 2,4,5-trichlorobiphenyl (PCB29), endosulfan or kepone was administered alone, the expression of NAG gene in cultured epidermal tissues was upregulated, while heptachlor had no effects. Under binary exposure to both 20-HE and an OC, a condition similar to the natural hormonal milieu of epidermal tissues of animals impacted by OCs, both Aroclor 1242 and endosulfan were found to be capable of antagonizing ecdysteroid signaling in cultured epidermal tissues. This antagonizing effect on epidermal ecdysteroid signaling can at least partly explain the inhibitory effects of these two agents on crustacean molting. PCB29, when given together with 20-HE, produced an additive effect on epidermal ecdysteroid signaling but such an additive effect was not observed when kepone was combined with 20-HE.

A molecular biomarker for disruption of crustacean molting: the N-acetyl-beta-glucosaminidase mRNA in the epidermis of the fiddler crab

Several environmentally persistent chemicals have been found to be capable of disrupting crustacean molting. Considering the importance of molting in the life of crustaceans, there is a need to develop a molecular biomarker that can reflect the disrupting effects of contaminants on ecdysteroid signaling in crustaceans. N-acetyl-beta-glucosaminidase (NAG) is a chitinolytic enzyme found in crustacean epidermis. The results of the present investigation show that the transcription of NAG gene in the epidermis of the fiddler crab, Uca pugilator, is inducible by the molting hormone 20-hydroxyecdysone, which validates the use of NAG mRNA as a biomarker for molt-disrupting effects of xenobiotics.

Nickel and binary metal mixture responses in Daphnia magna: molecular fingerprints and (sub)organismal effects

The recent development of a custom cDNA microarray platform for one of the standard organisms in aquatic toxicology, Daphnia magna, opened up new ways to mechanistic insights of toxicological responses. In this study, the mRNA expression of several genes and (sub)organismal responses (Cellular Energy Allocation, growth) were assayed after short-term waterborne metal exposure. Microarray analysis of Ni-exposed daphnids revealed several affected functional gene classes, of which the largest ones were involved in different metabolic processes (mainly protein and chitin related processes), cuticula turnover, transport and signal transduction. Furthermore, transcription of genes involved in oxygen transport and heme metabolism (haemoglobin, delta-aminolevilunate synthase) was down-regulated. Applying a Partial Least Squares regression on nickel fingerprints and biochemical (sub)organismal parameters revealed a set of co-varying genes (haemoglobin, RNA terminal phosphate cyclase, a ribosomal protein and an "unknown" gene fragment). An inverse relationship was seen between the mRNA expression levels of different cuticula proteins and available energy reserves. In addition to the nickel exposure, daphnids were exposed to binary mixtures of nickel and cadmium or nickel and lead. Using multivariate analysis techniques, the mixture mRNA expression fingerprints (Ni2+ + Cd2+, Ni2+ + Pb2+) were compared to those of the single metal treatments (Ni2+, Cd2+, Pb2+). It was hypothesized that the molecular fingerprints of the mixtures would be additive combinations of the gene transcription profiles of the individual compounds present in the mixture. However, our results clearly showed additionally affected pathways after mixture treatment (e.g. additional affected genes involved in carbohydrate catabolic processes and proteolysis), indicating interactive molecular responses which are not merely the additive sum of the individual metals. These findings, although indicative of the complex nature of mixture toxicity evaluation, underline the potential of a toxicogenomics approach in gaining more mechanistic information on the effects of single compounds and mixtures.

Elevated concentrations of ethinylestradiol, 17beta-estradiol, and medroxyprogesterone have little effect on reproduction and survival of Ceriodaphnia dubia

Wastewater effluent contains synthetic and natural hormones, often in complex mixtures, that may be associated with reproductive abnormalities in fish and other aquatic biota. We exposed the sentinel invertebrate Ceriodaphnia dubia to the natural estrogen 17beta-estradiol (E(2)), a synthetic estrogen, ethinylestradiol (EE(2)), and a synthetic progestin, medroxyprogesterone in a 7-day test. These compounds had no significant effect on reproduction or survival even at 10(6) times the concentrations at which reproductive effects have been documented in several fish species. C. dubia is routinely used for screening the toxicity of wastewater effluent. However, in the standard chronic 7-day exposure the endpoints of survival and reproduction were insensitive to several synthetic and natural vertebrate hormones. The C. dubia 7-day chronic toxicity test is probably not a useful monitoring tool for vertebrate hormones and their pharmaceutical analogs unless other sensitive endpoints such as maturation rates, molt frequency, and offspring sex ratios are incorporated in a practical manner.

Organochlorine pesticides (OCs) and polychlorinated biphenyls (PCBs) in sediments and crabs (Chasmagnathus granulata, Dana, 1851) from mangroves of Guanabara Bay, Rio de Janeiro State, Brazil

Organochlorinated compounds, seven indicator PCB congeners, DDT and its main metabolites, were determined in sediment and crab (Chasmagnathus granulata) samples collected from mangrove areas near Rio de Janeiro, Brazil. Samples were analysed according to the FAO/SIDA protocols using continuous non-polar solvent extraction and a conventional GC-ECD apparatus. The highest levels of total PCB congeners and total DDT metabolites in sediments (184.16 and 37.40 ng g(-1)d.w. respectively) and crab eggs (570.62 and 98.22 ng g(-1)d.w. respectively) were found at impacted mangroves. The higher PCB congeners than DDT metabolites levels suggesting a stronger industrial impact in this area. The results indicate that the population density of crab is negatively affected by sediment contamination that is reflected basically by the organochlorine content in the female eggs. The organochlorine concentration in eggs is more significant to evaluate or estimate an impact of these pollutants upon C. granulata population than the organochlorine concentration in sediment samples.