Towards an internationally harmonized test method for reproductive and developmental effects of endocrine disrupters in marine copepods

Endocrine disruption in crustaceans: New findings and perspectives

A significant advance has been made, especially during the last two decades, in the knowledge of the effects on crustacean species of pollutants proven to be endocrine disruptors in vertebrates. Such effects have been also interpreted in the light of recent studies on crustacean endocrinology. Year after year, the increased number of reports refer to the effects of endocrine disruptors on several processes hormonally controlled. This review is aimed at summarizing and discussing the effects of several kinds of endocrine disruptors on the hormonal control of reproduction (including gonadal growth, sexual differentiation, and offspring development), molting, and intermediate metabolism of crustaceans. A final discussion about the state of the art, as well as the perspective of this toxicological research line is given.

Long-term effects of neonicotinoids on reproduction and offspring development in the copepod Acartia tonsa

Neonicotinoids (NEOs) are neurotoxic pesticides acting as nicotinic acetylcholine receptor agonists. NEOs' efficacy against pest insects has favoured their spreading use in agriculture, but their proven effectiveness against non-target insects in terrestrial and aquatic ecosystems also raised concern over their environmental impact. Crustaceans were often studied for the impacts of NEOs due to their economic values and nervous' system similarity with insects. However, most studies on crustaceans focused on acute effects or exposure of early-life stages, while long-term effects were seldom explored. The present study aimed to assess the potential long-term effects of four commercially available NEOs on the reproduction and offspring of the calanoid copepod Acartia tonsa, a key species in the food webs of several coastal and estuarine environments. NEOs were confirmed as potent interferents of copepod reproduction. The first-generation compound acetamiprid significantly inhibited egg production and hatching ratio at 10 ng L-1, while larval survival and development were affected at 81 ng L-1. Similarly, the first-generation compound thiacloprid significantly inhibited the hatching ratio and larval development at 9 ng L-1, while it did not affect egg production and larval survival. Second-generation compounds were less toxic than acetamiprid and thiacloprid: clothianidin affected significantly only larval development of the offspring at 62 ng L-1, while thiamethoxam was not toxic at both the tested concentrations (8 ng L-1 and 84 ng L-1). These data evidenced that effects on copepods may occur at concentrations below the chronic aquatic life benchmarks reported by USEPA for acetamiprid (2100 ng L-1) and thiacloprid (970 ng L-1), suggesting that long-term effects of NEOs have been underestimated. A comparison with environmental concentrations evidenced that NEO-mediated effects on copepods are more liable in coastal areas receiving discharge from wastewater treatment plants or diffuse inputs from agricultural land during pesticide application periods.

Copepods as Indicators of Different Water Masses during the Northeast Monsoon Prevailing Period in the Northeast Taiwan

Simple Summary

How the origin and pathways of water masses can be traced by particular bioindicators remains an intriguing issue in biological oceanography. In the present zooplankton study focusing on copepods, calanoid copepodites were most abundant, with an average abundance of 774.24 ± 289.42 (inds. m⁻³) in the northeastern waters of Taiwan during the prevailing northeast monsoon, followed by the dominant copepod species Paracalanus aculeatus and Clausocalanus furcatus. According to hydrological parameters, the water masses were mainly derived from northeast monsoon surface waters, Kuroshio intrusion water, and mixed water masses. Indicator species were Temora turbinata, Calanopia elliptica, and Canthocalanus pauper in the northeast monsoon-derived water mass. Farranula concinna and Copilia mirabilis represented suitable indicators for the Kuroshio intrusion water mass in the research area. In the mixed water mass, the indicator species were Paracandacia truncata, Oncaea clevei, and P. aculeatus in the research area during the sampling campaign in late autumn.

Abstract

During this research, the average surface temperature, salinity, dissolved oxygen, and pH were 24.65 ± 1.53 (°C), 34.21 ± 0.07 (PSU), 6.85 ± 0.18 (mg/L), and 8.36 ± 0.03, respectively. Based on these environmental parameters, stations were arranged into three groups. Group A represents stations located around Keelung Island with the relative highest average dissolved oxygen, lowest average temperature, and pH values. Instead, the lowest average dissolved oxygen and highest average temperature, salinity, and pH values were recorded at the offshore stations. Keelung Island area was charged by cold water masses, which were driven by the Northeast monsoon, and stations in group C were affected by the Kuroshio Current. Kueishan Island area was mainly affected by mixed water masses resulting from the Kuroshio intrusion and monsoon-derived cold water. In this study, a total of 108 copepod species were identified, with an average abundance of 774.24 ± 289.42 (inds. m⁻³). Most species belong to the orders Calanoida and Poecilostomatoida, with an average relative abundance (RA) of 62.96% and 30.56%, respectively. Calanoid copepodites were the most dominant group, with a RA of 28.06%. This was followed by Paracalanus aculeatus, with a RA of 18.44%. The RA of Clausocalanus furcatus and Canthocalanus pauper was 4.80% and 3.59%, respectively. The dominant species P. aculeatus, C. pauper, Paracalanus parvus, and Temora turbinata were positively correlated with dissolved oxygen and negatively correlated with temperature in the surface waters. pH showed a negative correlation with P. parvus and T. turbinata, while the temperature was negatively correlated with these two dominant species. Indicator species were selected by an indicator value higher than 50%. Temora turbinata, Calanopia elliptica, C. pauper, Euchaeta concinna, Temora discaudata, Acartia pacifica, Macrosetella gracilis, Corycaeus speciosus, and P. parvus were considered as monsoonal cold water indicator species in Group A. Indicator copepod species for the Kuroshio Current were Farranula concinna, Copilia mirabilis, Candacia aethiopica, Corycaeus agilis, Farranula gibbula and Acrocalanus monachus in the study area. Paracandacia truncata, Oncaea clevei, P. aculeatus, and Centropages furcatus were considered suitable indicators for mixed water masses.

Metal contamination and heat stress impair swimming behavior and acetylcholinesterase activity in embryo-larval stages of the Mediterranean mussel, Mytilus galloprovincialis

Behavioral parameters are increasingly considered sensitive and early bioindicators of toxicity in aquatic organisms. A video-tracking tool was specifically developed to monitor the swimming behaviour of D-larvae of the Mediterranean mussel, Mytilus galloprovincialis, in controlled laboratory conditions. Both maximum and average swimming speeds and trajectories were recorded. We then investigated the impact of copper and silver with or without a moderate rise of temperature on swimming behavior and acetylcholinesterase (AChE) activity of mussel D-larvae and the possible mechanistic link between both biological responses. Our results showed that copper and/or silver exposure, as well as temperature increase, disrupts the swimming behavior of mussel larvae which could compromise their dispersal and survival. In addition, the combined effect of temperature and metals significantly (p < 0.05) increased AChE activity in mussel larvae. Pearson's correlation analysis was performed and results showed that the AChE activity is positively correlated with maximum speeds (r = 0.71, p < 0.01). This study demonstrates the value of behavioral analyzes of aquatic invertebrates as a sensitive and integrate marker of the effects of stressors.

Inhibition of Larval Development of Marine Copepods Acartia tonsa by Neonocotinoids

Neonicotinoids (NEOs) are neurotoxic pesticides widely used in agriculture due to their high effectiveness against pest insects. Despite their widespread use, very little is known about their toxicity towards marine organisms, including sensitive and ecologically relevant taxa such as copepods. Thus, we investigated the toxicity of five widely used NEOs, including acetamiprid (ACE), clothianidin (CLO), imidacloprid (IMI), thiacloprid (THI), and thiamethoxam (TMX), to assess their ability to inhibit the larval development of the copepod Acartia tonsa. The more toxic NEOs were ACE (EC₅₀ = 0.73 μg L⁻¹), TMX (EC₅₀ = 1.71 μg L⁻¹) and CLO (EC₅₀ = 1.90 μg L⁻¹), while the less toxic compound was IMI (EC₅₀ = 8.84 μg L⁻¹). Early life-stage mortality was unaffected by NEOs at all of the tested concentrations. The calculated toxicity data indicated that significant effects due to ACE (EC₂₀ = 0.12 μg L⁻¹), THI (EC₂₀ = 0.88 μg L⁻¹) and TMX (EC₂₀ = 0.18 μg L⁻¹) are observed at concentrations lower than established chronic aquatic life benchmarks reported by USEPA for freshwater invertebrates. Nevertheless, since environmental concentrations of NEOs are generally lower than the threshold concentrations we calculated for A. tonsa, the effects may be currently of concern only in estuaries receiving wastewater discharges or experiencing intense runoff from agriculture.

Acute and chronic toxicity assessments of 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) on the calanoid copepod Acartia clausi: Effects on survival, development, sex-ratio and reproduction

Estrogens, such as the 17β-estradiol (E2) and the 17α-ethinylestradiol (EE2), have been regarded as a global threat to aquatic ecosystems due to their pseudo-persistence, their high estrogenic activity and their toxicity towards non-target species. Data regarding their ecotoxicological effects on marine calanoid copepods are very scarce. In this study, the calanoid copepod Acartia clausi was used as a model organism for estrogens exposure in marine pelagic ecosystems. Lethal effects of estrogens on A. clausi life-stages (Embryos, one day old nauplii: N1, three day old nauplii: N3, copepodites: C1-C3 and adults: C6) were investigated using 48 h acute tests. Copepods showed stage-specific responses against E2 and EE2 acute exposure. The most resistant life stage was N1 with LC₅₀ values > 1500 μg L^-1 and >5000 μg L^-1, respectively for E2 and EE2. For N3, C1-C3, and C6, sensitivity to estrogens decreased with age and survival was affected at concentrations above those detected in the environment reflecting low estrogens acute toxicity for these life stages. In contrast, embryonic stage revealed high vulnerability to E2 and EE2 acute effects. Embryos showed non-monotonic dose-response and hatching success was significantly reduced at low realistic concentrations of E2 (0.005, 0.5, and 5 μg L^-1) and EE2 (0.05 and 5 μg L^-1). Survival, development and sex ratio of A. clausi to EE2 exposure at 1 and 100 μg L^-1 were also determined during a life cycle experiment. Fitness of the females of the generation F0 was evaluated by measuring lifespan, prosome length and egg production. The main observed effects were the decrease of females' prosome length, the feminization of the population and the reduction of the egg production for the generation F0 at 100 μg L^-1 of EE2. This concentration is above those reported in the environment indicating the tolerance of A. clausi to EE2 at environmentally relevant concentrations.

Alternative animal models in predictive toxicology

Toxicity testing relies heavily on animals, especially rodents as part of the non-clinical laboratory testing of substances. However, the use of mammalians and the number of animals employed in research has become a concern for institutional ethics committees. Toxicity testing involving rodents and other mammals is laborious and costly. Alternatively, non-rodent models are used as replacement, as they have less ethical considerations and are cost-effective. Of the many alternative models that can be used as replacement models, which ones can be used in predictive toxicology? What is the correlation between these models and rodents? Are there standardized protocols governing the toxicity testing of these commonly used predictive models? This review outlines the common alternative animal models for predictive toxicology to address the importance of these models, the challenges, and their standard testing protocols.

Susceptibility of the Non-Targeted Crustacean Eurytemora affinis to the Endocrine Disruptor Tebufenozide: A Transcriptomic Approach

Copepods are zooplanktonic crustaceans ubiquitously widespread in aquatic systems. Although they are not the target, copepods are exposed to a wide variety of pollutants such as insect growth regulators (IGRs). The aim of this study was to investigate the molecular response of a non-targeted organism, the copepod Eurytemora affinis, to an IGR. Adult males and females were exposed to two sub-lethal concentrations of tebufenozide (TEB). Our results indicate a sex-specific response with a higher sensitivity in males, potentially due to a differential activation of stress response pathways. In both sexes, exposure to TEB triggered similar pathways to those found in targeted species by modulating the transcription of early and late ecdysone responsive genes. Among them were genes involved in cuticle metabolism, muscle contraction, neurotransmission, and gametogenesis, whose mis-regulation could lead to moult, locomotor, and reproductive impairments. Furthermore, genes involved in epigenetic processes were found in both sexes, which highlights the potential impact of exposure to TEB on future generations. This work allows identification of (i) potential biomarkers of ecdysone agonists and (ii) further assessment of putative physiological responses to characterize the effects of TEB at higher biological levels. The present study reinforces the suitability of using E. affinis as an ecotoxicological model.

Density-Dependent Metabolic Costs of Copper Exposure in a Coastal Copepod

Traditional ecotoxicology methods involving copepods have focused on exposure of pooled individuals and averaged responses, but there is increasing awareness of the importance of individual variation. Many biological traits are density dependent, and decisions to use single-individual or pooled exposure may affect responses to anthropogenic stressors. We investigated how conspecific density as a biotic stressor affects behavioral and respiratory responses to copper (Cu) exposure in the coastal copepod Tigriopus brevicornis. Adults were incubated at densities of 1, 2, or 4 individuals per replicate in 3.2 mL of exposure medium (23 µg Cu L^-1 or control). Our results show an interaction of Cu exposure and density on respiration. The Cu exposure increased respiration, but this effect diminished with increasing density. We also found reduced swimming activity with increasing density. We propose 2 nonexclusive alternative explanations for the density-dependent respiratory increase of Cu exposure: 1) a behavioral stress response to low conspecific density, or 2) increased Cu exposure due to increased swimming activity. We emphasize the importance of considering density-dependency in responses when designing and interpreting ecotoxicology studies. Environ Toxicol Chem 2021;40:2538-2546. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

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.

Assessment of the relative sensitivity of the copepods Acartia tonsa and Acartia clausi exposed to sediment-derived elutriates from the Bagnoli-Coroglio industrial area

The sensitivity of the copepods Acartia tonsa, commonly used in standardized tests for environmental risk assessment and A. clausi, the dominant autochthonous congener species in the Mediterranean Sea, was assessed using sediment-derived elutriates from the industrial area of Bagnoli-Coroglio and nickel chloride as referent toxicant. Acute A. clausi naupliar immobilization test showed EC₅₀ for elutriates E25, E56 and E84 of 23.3%, 80.5% and >100%, respectively, compared to 59.5%, 66.6% and >100% in A. tonsa. In the 7 day sublethal test, a reduction in A. clausi egg production rates was observed in all elutriates, but only in E56 for A. tonsa. Elutriate 56, which contained the highest amount of polycyclic aromatic hydrocarbons, also induced 70% mortality in A. clausi females. Although A. clausi was more sensitive than A. tonsa, the two species had convergent responses to the three elutriates, thus opening the venue for a potential use of A. clausi in standardized ecotoxicity tests.

Genotoxic Response and Mortality in 3 Marine Copepods Exposed to Waterborne Copper

Copper (Cu) is an essential trace metal, but may also be toxic to aquatic organisms. Although many studies have investigated the cytotoxicity of Cu, little is known about the in vivo genotoxic potential of Cu in marine invertebrates. We investigated the genotoxicity of Cu in 2 pelagic calanoid copepods, Acartia tonsa and Temora longicornis, and the intertidal harpacticoid copepod Tigriopus brevicornis by exposing them for 6 and 72 h to waterborne Cu (0, 6, and 60 µg Cu/L). A subsequent 24-h period in filtered seawater was used to investigate delayed effects or recovery. Genotoxicity was evaluated as DNA strand breaks in individual copepods using the comet assay. Copper did not increase DNA strand breaks in any of the species at any concentration or time point. The treatment did, however, cause 100% mortality in A. tonsa following exposure to 60 µg Cu/L. Acartia tonsa and T. longicornis were more susceptible to Cu-induced mortality than the benthic harpacticoid T. brevicornis, which appeared to be unaffected by the treatments. The results show major differences in Cu susceptibility among the 3 copepods and also that acute toxicity of Cu to A. tonsa is not directly associated with genotoxicity. We also show that the comet assay can be used to quantify genotoxicity in individual copepods. Environ Toxicol Chem 2019;38:2224-2232. © 2019 SETAC.

Use of scanning and image recognition technology to semi-automate larval development assessment in toxicity tests with a tropical copepod

There is a high demand for the development of reliable chronic toxicity tests using tropical marine species for subsequent use in tropical risk assessment. However, many chronic test endpoints can be laborious and time-consuming to assess, particularly if the endpoints require measurements of individuals (e.g. growth, size) or advanced taxonomic expertise (e.g. differentiating between larval development stages). In this study, we used scanning and image recognition (SIR) technology to develop and validate a chronic toxicity test with larvae of the tropical euryhaline copepod, Acartia sinjiensis. Optimisation steps are described, and included egg age, and effect of algal food type and salinity on toxicity. Comparisons were made between traditional endpoints measured using microscopy and those measured using SIR. Traditional endpoints of larval development ratio (LDR) and survival achieved using microscope examination and SIR were almost identical (R² = 0.96-0.97). Additional endpoints made possible by SIR included larval development index (LDI; based on the number of animals at different stages of development), and a range of size measurements (e.g. surface area, perimeter and length) for individual animals and for total populations (i.e. a proxy for biomass). The SIR-derived endpoints were based on measurements that had concentration-dependant responses to tested toxicants (copper, nickel, ammonia), and were a sub-set of the full range of metrics provided by the software. Toxicity values based on SIR-measurements were similar to or more sensitive than the traditional LDR endpoint. SIR technology provides a major opportunity to improve and modernise larval development tests for a range for species, but comes at a cost of increased data size and complexity. Therefore, as a research tool, SIR has significant advantages over traditional microscope methods, but for routine toxicity testing, SIR incorporation into invertebrate toxicity testing will benefit from further improvements to the associated software and data management systems.

Development of acute and chronic toxicity bioassays using the pelagic copepod Gladioferens pectinatus

Well validated and reliable biological assays using local and native species are required to characterise the impacts of pollution on ecosystem health. We identified a native estuarine pelagic copepod species suitable for assessing the ecotoxicological impact of anthropogenic contaminants. Gladioferens pectinatus fulfilled the necessary-selection criteria of: wide distribution and abundance across New Zealand estuaries, ease of maintenance in the laboratory, short life cycle, sensitivity to toxicants with different modes of action, and providing reproducibility of biological response to toxicants. Measured endpoints were survival and larval development rate for the nauplii, and survival, realized offspring and total potential offspring for adults. LC₅₀ values for the survival of G. pectinatus exposed to copper, phenanthrene and chlorpyrifos were 170 (143-193), 181.3 (131.3-231.3) and 4.3 (3.8-4.9) µg/L, respectively. The most sensitive chronic endpoint identified for G. pectinatus was the larval development rate, with EC₅₀ values of 49.8 (45-55.3), 31.3 (24.8-44.7) and 1.97 (1.6-2.31) µg/L for copper, phenanthrene and chlorpyrifos, respectively. The acute and chronic responses obtained for G. pectinatus against the three reference toxicants are comparable with those reported for other copepod species and confirm its sensitivity and suitability to assess the toxicity of New Zealand estuarine samples.

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.

A full life-cycle bioassay with Cantareus aspersus shows reproductive effects of a glyphosate-based herbicide suggesting potential endocrine disruption

A full life-cycle (240 days) bioassay using the terrestrial snail, Cantareus aspersus, allowing exposure during embryogenesis and/or the growth and reproduction phases, was used to assess the effects of Bypass®, a glyphosate-based herbicide (GlyBH), on a range of endpoints, including parameters under endocrine control. As a positive control, a mixture (R-A) made of diquat (Reglone®) and nonylphenols (NP, Agral®), known for its endocrine disrupting effects in other organisms, was tested. At environmental concentrations, both pesticides (R-A mixture and GlyBH) enhanced growth but reduced reproduction. The R-A mixture acted mainly on the fecundity through a delay in egg-laying of approximately 20 days and a strongly reduced number of clutches. This latter dysfunction may be caused by a permanent eversion of the penis, suggesting a disrupting effect at the neuro-endocrine level, which prevented normal mating. GlyBH acted on fertility, possibly due to a decrease in the fertilization of eggs laid by adults exposed during their embryonic development. These results, associated with the absence of observed effects on gonad histology of GlyBH exposed snails, suggested that the underlying mechanisms are neuro-endocrine.

Proteomic response of Macrobrachium rosenbergii hepatopancreas exposed to chlordecone: Identification of endocrine disruption biomarkers?

The present work is the first study investigating the impacts of chlordecone, an organochlorine insecticide, on the proteome of the decapod crustacean Macrobrachium rosenbergii, by gel-free proteomic analysis. The hepatopancreas protein expression variations were analysed in organisms exposed to three environmental relevant concentrations of chlordecone (i.e. 0.2, 2 and 20µg/L). Results revealed that 62 proteins were significantly up- or down-regulated in exposed prawns compared to controls. Most of these proteins are involved in important physiological processes such as ion transport, defense mechanisms and immune system, cytoskeleton dynamics, or protein synthesis and degradation. Moreover, it appears that 6% of the deregulated protein are involved in the endocrine system and in the hormonal control of reproduction or development processes of M. rosenbergii (e.g. vitellogenin, farnesoic acid o-methyltransferase). These results indicate that chlordecone is potentially an endocrine disruptor compound for decapods, as already observed in vertebrates. These protein modifications could lead to disruptions of M. rosenbergii growth and reproduction, and therefore of the fitness population on the long-term. Besides, these disrupted proteins could be suggested as biomarkers of exposure for endocrine disruptions in invertebrates. However, further investigations are needed to complete understanding of action mechanisms of chlordecone on proteome and endocrine system of crustaceans.

Effects of anti-androgens cyproterone acetate, linuron, vinclozolin, and p,p'-DDE on the reproductive organs of the copepod Acartia tonsa

The study was performed to detect the effects of anti-androgenic compounds on the reproduction. In this paper alterations observed in the marine calanoid copepod Acartia tonsa exposed to environmental concentrations of cyproterone acetate (CPA), linuron (LIN), vinclozolin (VIN), and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE) for 21 days covering a full life cycle are described. Histological alterations were studied with a focus on reproductive organs, gonad and accessory sexual glands. Exposure to ≥1.2 µg L(-1) CPA caused degeneration of spermatocytes and deformation of the spermatophore in males. In a single male exposed to 33 µg L(-1) CPA, an ovotestis was observed. In CPA exposed females, enhancement of oogenesis, increase in apoptosis and a decrease in proliferation occurred. Exposure of males to ≥12 µg L(-1) LIN caused degenerative effects in spermatogonia, spermatocytes and spermatids, and at 4.7 µg L(-1) LIN, the spermatophore wall displayed an irregular formation. In LIN exposed females, no such structural alterations were found; however, the proliferation index was reduced at 29 µg L(-1) LIN. At an exposure concentration of ≥100 µg L(-1) VIN, distinct areas in male gonad were stimulated, whereas others displayed a disturbed spermatogenesis and a deformed spermatophore wall. In VIN exposed female A. tonsa, no effects were observed. Male A. tonsa exposed to p,p'-DDE displayed an impairment of spermatogenesis in all stages with increased degrees of apoptosis. In p,p'-DDE-exposed females, a statistical significant increase of the proliferation index and an intensification of oogenesis were observed at 0.0088 µg L(-1).

Vitellogenin and vitellogenin receptor gene expression and 20-hydroxyecdysone concentration in Macrobrachium rosenbergii exposed to chlordecone

Chlordecone is a persistent organochlorine pesticide widely used in Guadeloupe (French West Indies) to control the banana weevil Cosmopolites sordidus. Although it was previously highlighted that chlordecone may affect the reproduction and growth of vertebrate species, little information is available on the chlordecone effects in invertebrates. The present study investigated the effects of chlordecone on a hormone and a protein having key roles in reproduction and growth of the decapod crustacean Macrobrachium rosenbergii, by measuring the 20-hydroxyecdysone concentration, vitellogenin, and vitellogenin receptor gene expression, as well as the bioconcentration of chlordecone in exposed prawns. First, the results revealed that chlordecone was accumulated in M. rosenbergii. Then, it was found that Vg and VgR gene expression were increased in male and female M. rosenbergii exposed to chlordecone for 90 and 240 days, while the 20-hydroxyecdysone concentrations were decreased. This work suggests that chlordecone accumulates in prawn tissues and could affect key molecules involved in the reproduction and the growth of the invertebrate M. rosenbergii. However, many questions remain unresolved regarding the impacts of chlordecone on growth and reproduction and the signaling pathways responsible for these effects, as well as the potential role of confounding factors present in in situ studies.

Toxicity of sediments from a mangrove forest patch in an urban area in Pernambuco (Brazil)

Industrial and urban residues are discharged every day to the rivers and may arrive at the mangrove forest and prejudice the quality of the environment and the organisms present there. The mangrove forest patch studied is encircled by an urban area of the city of Recife (Brazil) that has approximate 1.5 million inhabitants and is one of the most industrialized centers in Northeast Brazil. The aim of this study was to assess the quality of the sediments of this mangrove patch in terms of metal contamination and ecotoxicology. Samples of surface sediment were collected in six stations for toxicological tests and trace metal determination (Cr, Zn, Mn, Fe, Cu, Pb, Co and Ni), in July and August, 2006 (rainy season); and in January and February 2007 (dry season). Toxicity tests with solid-phase sediments were carried out with the copepod Tisbe biminiensis in order to observe lethal and sub-lethal endpoints and correlate them with chemical data. In June, there were no observed lethal effect, but two stations presented sub-lethal effects. In January, lethal effect occurred in three stations and sub-lethal in one station. The levels for Zn and Cr were at higher levels than international proposed guidelines (NOAA). There was a negative significant correlation between the copepods׳ fecundity, and Zn and Cr concentrations. Therefore, the studied sediments can be considered to have potential toxic to benthos due to the high content of Zn and Cr.

Developmental endpoints of chronic exposure to suspected endocrine-disrupting chemicals on benthic and hyporheic freshwater copepods

The aims of this study were: (i) to assess if carbamate pesticides and ammonium, widely detected in European freshwater bodies, can be considered ecologically relevant endocrine-disrupting chemicals (EDCs) for benthic and interstitial freshwater copepods; and (ii) to evaluate the potential of copepods as sentinels for monitoring ecosystem health. In order to achieve these objectives, four species belonging to the harpacticoid copepod genus Bryocamptus, namely B. (E.) echinatus, B. (R.) zschokkei, B. (R.) pygmaeus and B. (B.) minutus, were subjected to chronic exposures to Aldicarb and ammonium. A significant deviation from the developmental time of unexposed control cultures was observed for all the species in test cultures. Aldicarb caused an increase in generation time over 80% in both B. minutus and B. zschokkei, but less than 35% in B. pygmaeus and B. echinatus. Ammonium increased generation time over 33% in B. minutus, and 14, 12 and 3.5% for B. pygmaeus, B. zschokkei and B. echinatus, respectively. On the basis of these results it can be concluded that chronic exposure to carbamate pesticides and ammonium alters the post-naupliar development of the test-species and propose their potential role as EDCs, leaving open the basis to search what are the mechanism underlying. A prolonged developmental time would probably produce a detrimental effect on population attributes, such as age structure and population size. These deviations from a pristine population condition may be considered suitable biological indicators of ecosystem stress, particularly useful to compare polluted to unpolluted reference sites. Due to their dominance in both benthic and interstitial habitats, and their sensitivity as test organisms, freshwater benthic and hyporheic copepods can fully be used as sentinel species for assessing health condition of aquatic ecosystems as required by world-wide water legislation.

A new protocol for ecotoxicological assessment of seawater using nauplii of Tisbe biminiensis (Copepoda:Harpacticoida)

Copepods are largely used in toxicity tests. The nauplii of these organisms are more sensitive to contaminants than the adult stage. The aim of the present study was to test a protocol for the use of nauplii of the copepod Tisbe biminiensis in the ecotoxicological assessment of seawater. The sensitivity of these organisms to zinc sulphate (ZnSO4·7H2O) was also determined. The following conditions were established for the protocol based on the best development of nauplii to copepodites: 72-h duration, the microalga Chaetocerus gracilis at 2.5×10(5)cellsmL(-1) as feed and incubation temperature of 28°C. In the zinc sulphate sensitivity tests, EC50-72 h and LC50/72 h were 3.25±0.59 mg L(-1) and 3.46±0.72 mg L(-1), respectively, as estimated by the final number of copepodites and total number of live animals in relation to the mean number of inoculated nauplii. The estimated NOEC was 2.0 mg L(-1). The test developed is fast and not labour intensive. T. biminiensis nauplii exhibit sensitivity to zinc sulphate similar to that of other species of copepods employed in water toxicity tests, demonstrating the usefulness of these organisms in ecotoxicological studies involving samples of environmental seawater.

Acute and chronic toxicity study of the water accommodated fraction (WAF), chemically enhanced WAF (CEWAF) of crude oil and dispersant in the rock pool copepod Tigriopus japonicus

We determined the toxicity of the water accommodated hydrocarbon fraction (WAF), two chemically enhanced WAFs (CEWAFs; CEWAF-C, Crude oil+Corexit 9500 and CEWAF-H, Crude oil+Hiclean) of crude oil and two dispersants (Corexit 9500 and Hiclean) to the rock pool copepod Tigriopus japonicus. In the acute toxicity test, Corexit 9500 was the most toxic of all the chemicals studied. The nauplius stage of T. japonicus was more susceptible to the toxic chemicals studied than the adult female. The toxicity data using the nauplius stage was then considered as baseline to determine the spiking concentration of chemicals for chronic toxicity tests on the copepod. As the endpoints in the chronic toxicity test, survival, sex ratio, developmental time and fecundity of the copepod were used. All chemicals used in this study resulted in increased toxicity in the F1 generation. The lowest-observed-adverse-effect (LOAE) concentrations of WAF, CEWAF-H, CEWAF-C, Hiclean and Corexit 9500 were observed to be 50%, 10%, 0.1%, 1% and 1%, respectively. The results in present study imply that copepods in marine may be negatively influenced by spilled oil and dispersant.

Expression profile analysis of antioxidative stress and developmental pathway genes in the manganese-exposed intertidal copepod Tigriopus japonicus with 6K oligochip

Manganese (Mn) provides one of aquatic pollutants in marine ecosystem. Here we used a 6K oligomicroarray to identify the effect of Mn on transcriptomes in the copepod Tigriopus japonicus. A total of 5594 spots were significantly modulated on a 6K oligomicroarray with hierarchical clustering after exposure to Mn over 24h. Of them, 186 and 489 genes were significantly upregulated and downregulated, respectively. Particularly, several genes involved in stress, detoxification, and developmental functions were significantly modulated in T. japonicus exposed for 24h. In detail, Mn exposure specifically up-regulated genes that were related to intracellular stress, antioxidant, and detoxification pathways such as cytochrome P450s (CYPs), glutathione S-transferases (GSTs), and heat shock proteins (hsps), while a majority of downregulated genes was associated with developmental pathways such as cuticle protein, ecdysone receptor, and vitellogenin. These results demonstrated that Mn exposure modulated gene expression in relation to intracellular stress, leading to developmental retardation in the intertidal copepod, T. japonicus, and provide a better understanding of mechanistic molecular studies of Mn-induced cellular damage.

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.

Acute toxicity of crude oil water accommodated fraction on marine copepods: the relative importance of acclimatization temperature and body size

Recent oil spillage accidents around the world greatly increase harmful risks to marine ecology. This study evaluated the influences of petroleum water accommodated fraction (WAF) on 15 typical species of marine copepods collected from a subtropical bay in East China Sea at different seasons. Copepods showed impaired swimming ability, restlessness, loss of balance, anoxic coma, and even death when they were acutely exposed to the crude oil WAF under laboratory conditions. The LC(50) values (expressed in total petroleum hydrocarbon concentration) indicated that the tolerances of copepods to WAF decreased significantly (P < 0.05) with increased exposure duration and natural water temperatures (acclimatization temperature). The sensitivity of the copepods was species-specific (P < 0.01), and there was a significant (P < 0.05) positive correlation between the 48-h LC(50) and body size. Therefore, the small copepod species confront more survival challenges under oil contamination stress, especially in the warm months or regions.

An individual-based modeling approach for evaluation of endpoint sensitivity in harpacticoid copepod life-cycle tests and optimization of test design

In the present study, an individual-based model for Nitocra spinipes was developed and used to optimize the test design of a proposed Organisation for Economic Co-operation and Development test guideline for harpacticoid copepods. The variability between individuals was taken into account, based on measured data, leading to stochastic model output. Virtual experiments were performed with the model to analyze the endpoint sensitivity and the effect of number of replicates and inspection intervals on statistical power. The impact of mortality was evaluated; most sublethal effects could not be determined if the mortality was ≥70%. Most sensitive to mortality was the determination of effects on brood size, for which the statistical power was reduced at 10% mortality. Our simulations show that increasing the number of replicates from 72 to 96 or 144 has little impact on the statistical power, whereas 25 replicates disallow relevant endpoint detection. Furthermore, it was demonstrated that the proposed 1D inspection interval can be shifted to a 3D interval, without losing statistical power. It was demonstrated that developmental endpoints have a higher statistical power than reproductive endpoints in the current test design. The present study highlights the usefulness of individual-based models for optimizing the experimental design. The use of such models in the development of standard test guidelines will lead to a faster and less resource-demanding process.

A proteomics based approach to assessing the toxicity of bisphenol A and diallyl phthalate to the abalone (Haliotis diversicolor supertexta)

The contamination of marine ecosystems by endocrine disrupting compounds (EDCs) is of great concern. Protein expression profile maybe a good method to help us understand the molecular mechanisms of EDCs-toxicity to aquatic organisms. In this study, the abalone (Haliotis diversicolor supertexta), was selected as the target organism. Toxicological effects of two reference endocrine disruptors: diallyl phthalate (DAP, 50microgL(-1)) and bisphenol-A (BPA, 100microgL(-1)) were investigated after a three months static-renewal exposure on abalones using proteomics to analyze their hepatopancreas tissues. Some enzyme activity parameters of hepatopancreas extracts were also performed, including Na(+)-K(+)-ATPase, Ca(2+)-Mg(2+)-ATPase, peroxidase (POD) and malondialdehyde (MDA) production. After analyzing the proteomics profile of hepatopancreas by 2D gel electrophoresis, we found that 24 spots significantly increased or decreased at protein expression level (2-fold difference) in the 2D-maps from the treatment groups. Eighteen out of 24 protein spots were successfully identified by matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry (MALDI-TOF-MS). These proteins can be roughly categorized into diverse functional classes such as detoxification, oxidative stress, hormone regulating, cellular metabolism and innate immunity. In addition, the enzymatic results indicated that DAP/BPA exposure affected the oxidative stress status and the cellular homeostasis, which partly corroborated the proteomics' results. Taken together, these data demonstrate that proteomics is a powerful tool to provide valuable insights into possible mechanisms of toxicity of EDCs contaminants in aquatic species. Additionally, the results highlight the potential of abalone as a valuable candidate for investigating EDCs impacts on marine ecosystems.

Short-term toxicity tests on the harpacticoid copepod Tisbe battagliai: lethal and reproductive endpoints

Short-term bioassays based on lethal and reproductive responses of Tisbe battagliai were applied to determine responses of copepods to copper and LAS. Percentage of spawning females, fecundity (F), and total newborn production (N) for 48 and 72 h were calculated for both substances. It was observed percentage of spawning females was not affected by sublethal concentrations of both compounds. Following values were obtained: EC(50)(N)-48 h of 670+/-30 microgLASL(-1) and EC(50)(F)-48 h of 670+/-30 microgLASL(-1); and EC(50)(N)-72 h of 44.5+/-1.8 microgCuL(-1) and EC(50)(F)-72 h of 30.8+/-1.1 microgCuL(-1). Lethal effects of the two substance-types were also assessed, obtaining the LC(50)-24h of 1980+/-160 microgLASL(-1); and LC(50)-48 h of 83.1+/-10.5 microgCuL(-1) for nauplii; and LC(50)-72 h of 157+/-25 microgCuL(-1), and LC(50)-72 h of 2660+/-270 microgLASL(-1) for adults. Fecundity and total newborn production are sensitive endpoints for determining effects of toxicants.

Detecting points as developmental delay based on the life-history development and urosome deformity of the harpacticoid copepod, Tigriopus japonicus sensu lato, following exposure to benzo(a)pyrene

To identify ecotoxicological responses to an endocrine disrupter, benzo(a)pyrene, we examined the life-history of the harpacticoid copepod, Tigriopus japonicus sensu lato. Based on the life-history of copepods, survival rate of nauplii (NSR) and copepodites (CSR), copepodite emergence day (CED) and adult male emergence day (AMED), sex ratio (MER), brooding success rate (BSR), and first brooding day of adult females (FBD) were measured. Significant differences were observed in the survival and development of nauplii (NSR and CED) and sex ratio (MER) of exposed and non-exposed copepods. Moreover, high concentration of BaP can be lethal to copepodite and exhibited a delay of growth. In this study, the CED and AMED among ecotoxicological response based on life-history developments were delayed and the body characteristics decreased in response to exposure to benzo(a)pyrene. The dwarfism and urosome deformity of the T. japonicus s.l. was exhibited in response to chemical exposure. Specifically, the body characteristics and biomass of dwarf copepods that had been exposed to benzo(a)pyrene were 30% and 50% lower than the control group, respectively. The incidence of abnormal urosomes was divided into two types. The first deformity type was signs of shrinkage in the middle of the urosome or the entire urosome was narrower than those of the control organisms. In the second type, the anal somite and the distal side of the urosome had abnormally swelled. Taken together, the nauplii and copepodid development of T. japonicus s.l. can be used as a useful biomaker for detecting developmental delay based on their entire life-history. In addition, the urosome deformity was used a good potential monitoring tool invading various chemicals and environmental contamination into water system.

A critical analysis of the biological impacts of plasticizers on wildlife

This review provides a critical analysis of the biological effects of the most widely used plasticizers, including dibutyl phthalate, diethylhexyl phthalate, dimethyl phthalate, butyl benzyl phthalate and bisphenol A (BPA), on wildlife, with a focus on annelids (both aquatic and terrestrial), molluscs, crustaceans, insects, fish and amphibians. Moreover, the paper provides novel data on the biological effects of some of these plasticizers in invertebrates, fish and amphibians. Phthalates and BPA have been shown to affect reproduction in all studied animal groups, to impair development in crustaceans and amphibians and to induce genetic aberrations. Molluscs, crustaceans and amphibians appear to be especially sensitive to these compounds, and biological effects are observed at environmentally relevant exposures in the low ng l(-1) to microg l(-1) range. In contrast, most effects in fish (except for disturbance in spermatogenesis) occur at higher concentrations. Most plasticizers appear to act by interfering with the functioning of various hormone systems, but some phthalates have wider pathways of disruption. Effect concentrations of plasticizers in laboratory experiments coincide with measured environmental concentrations, and thus there is a very real potential for effects of these chemicals on some wildlife populations. The most striking gaps in our current knowledge on the impacts of plasticizers on wildlife are the lack of data for long-term exposures to environmentally relevant concentrations and their ecotoxicity when part of complex mixtures. Furthermore, the hazard of plasticizers has been investigated in annelids, molluscs and arthropods only, and given the sensitivity of some invertebrates, effects assessments are warranted in other invertebrate phyla.

Gene expression profiling of copper-induced responses in the intertidal copepod Tigriopus japonicus using a 6K oligochip microarray

The intertidal copepod Tigriopus japonicus has shown promising results in classical acute and chronic toxicity studies. Recently, a large number of genes have been identified from this species and their mRNA expression has been studied independently against exposure to marine environmental pollutants. T. japonicus is a promising organism for the study of mechanistic aspects of marine environmental pollutants using genomics. In this study, a 6K oligochip for T. japonicus that included mostly unique sets of genes from approximately 26K ESTs, was developed. A total of 5463 spots (2313 mRNAs upregulated and 3150 downregulated) were identified to be significantly expressed on microarray by hierarchical clustering of genes after exposure to copper for different time durations (10 microg/L for 6, 12 and 24h). However, mRNAs of only 138 and 375 genes were observed to be consistently upregulated and downregulated, respectively, at all time points. Most of the changes of mRNA expression were observed at the short exposure of 6h. It was observed that mRNA expression of several genes involved in growth, metabolism, reproduction and hormonal regulation was modulated in Cu-exposed T. japonicus. mRNA expression of genes involved in detoxification and antioxidant functions was also modulated. This indicates that Cu-induced gene transcription is complicated in T. japonicus similar to other crustaceans. Cu specifically upregulated mRNAs of genes of some isoforms of cytochrome P450 (CYP). On the other hand, a majority of downregulated mRNAs were of genes encoding for proteins important for growth and development. The expression profile of mRNAs of selected genes was verified by the quantitative real time RT-PCR. The mRNA expression profiles provide insight into the mechanism of action of copper in T. japonicus. These results demonstrate the suitability of a T. japonicus oligochip microarray for risk assessment of trace metals in the marine environment. As yet, major breakthroughs in invertebrate toxicogenomics have mainly been in Daphnia and Drosophila. Daphnia's use is limited to freshwater ecotoxicogenomics. Here we propose an oligochip microarray-based approach for risk assessment of trace metals in a potential model marine test species.

Lethal and sublethal effects of naphthalene and 1,2-dimethylnaphthalene on naupliar and adult stages of the marine cyclopoid copepod Oithona davisae

Short-term (24h) exposure experiments have been conducted to determine the effects of two environmental relevant polycyclic aromatic hydrocarbons (PAHs), naphthalene (NAPH) and dimethylnaphthalene (C2-NAPH), on the naupliar and adult stages of the marine cyclopoid copepod Oithona davisae. To resemble more realistic conditions, those exposure experiments were conducted under the presence of food. The naupliar stages evidenced lower tolerance to PAH exposure regarding narcotic and lethal effects than adults. Copepod feeding activity showed to be very sensitive to the presence of the studied PAHs, detrimental effects occurring at toxic concentrations ca. 2-3 fold lower than for narcotic effects. In addition we report PAH-mediated changes in cell size and growth rate of the prey item, the heterotrophic dinoflagellate Oxyrrhis marina, that could indirectly affect copepod feeding and help explain hormesis-like responses in our feeding experiments.

Two-generation toxicity study on the copepod model species Tigriopus japonicus

Previous studies on the intertidal copepod Tigriopus japonicus have demonstrated that it is a suitable model species for the assessment of acute toxicities of marine pollutants. In order to standardize T. japonicus for use in environmental risk assessment involving whole life cycle exposure, we tested nine pollutants for their effects on growth and reproduction during a two-generation life cycle exposure test. Nauplii (F 0) were exposed to a range of concentrations of each chemical in a static renewal culture system. Broods of the second generation (F1) were subsequently exposed to the same concentrations for one full life cycle. Of the seven traits (nauplius phase, development time, survival, sex ratio, number of clutch, nauplii per clutch and fecundity), only the length of the nauplius phase and development time showed a greater sensitivity to chemical exposure. Between the two sensitive traits, the period of the nauplius phase was more sensitive than cohort generation time. Biocides significantly increased the maturation period of nauplii as well as copepodids in F 0 generation. In this study, it was demonstrated that T. japonicus could also be used in reproduction and life cycle tests and it provides an opportunity for testing the chronic and subchronic toxic effects of marine pollutants. Further validation and harmonization in a multi-centric study involving other laboratories of the region will strengthen its use as a supplement to existing model species.

Acute toxicities of trace metals and common xenobiotics to the marine copepod Tigriopus japonicus: Evaluation of its use as a benchmark species for routine ecotoxicity tests in Western Pacific coastal regions

Marine copepods have recently been recognized as important organisms in ecotoxicity testing for regulatory purposes. The harpacticoid copepod Tigriopus japonicus has a wide geographical distribution along the coast in the Western Pacific including Japan, South Korea, Taiwan, and Hong Kong. This study evaluated the acute toxicity sensitivity profile of Tigriopus japonicus against 12 common toxic substances including six endocrine disrupting chemicals (EDCs), three biocides and three trace metals. Through standard acute toxicity test procedures, toxicity endpoints LC(50), LC(10), and no observed effect concentration (NOEC) of each chemical were obtained. Although T. japonicus depicted different sensitivities towards different chemicals, a dose-response relationship was consistent in all cases. T. japonicus was particularly sensitive to most of the EDCs, but relatively less sensitive to molinate (a thiocarbate herbicide). Across all tested chemicals, tributyltin (TBT) was the most toxic to the copepod with the LC(50), LC(10), and NOEC of 0.05, 0.03, and 0.02 mg/L, respectively. A comparison made with available data on acute toxicities of these chemicals to other marine copepod species revealed that T. japonicus is generally more sensitive to EDCs and in particular to TBT. We, therefore, strongly advocate that T. japonicus shall be adopted as a benchmark marine species for routine ecotoxicity testing and ecotoxicological studies in Western Pacific coasts.

The water flea Daphnia magna (Crustacea, Cladocera) as a test species for screening and evaluation of chemicals with endocrine disrupting effects on crustaceans

The water flea Daphnia magna (Crustacea, Cladocera) is a cyclical parthenogen, which can reproduce both by parthenogenesis and by sexual reproduction. With its ease of handling in the laboratory, several testing methods using D. magna exist for regulatory toxicity testing. Recently, several studies revealed that one of the major hormone groups in insects and crustaceans, juvenile hormones, are involved in the shift of reproductive mode from parthenogenesis to sexual reproduction (production of male neonates). Using offspring sex ratio as a new endpoint has made it possible to identify chemicals with juvenile hormone-like effects on crustaceans. The testing method using D. magna, in which offspring sex ratio is incorporated as a new endpoint, is now being proposed to the OECD as an enhanced version of the existing OECD Test Guideline 211: Daphnia magna reproduction test. No other clear-cut endpoint for identifying juvenile-hormone disrupting effects has ever been found in crustaceans than the induction of male neonates production in cladocerans. In this regard, it is expected that testing methods using D. magna are suitable for screening and risk assessment of chemicals with juvenile-hormone disrupting effects.

Crustacean endocrine toxicology: a review

Crustaceans are major constituents to aquatic ecosystems that provide a variety of ecological and economic services. Individual crustacean species are adept at occupying diverse niches and their success, in part, stems from neuro-endocrine signaling cascades that regulate physiology in response to environmental and internal cues. Peptide hormones are major signal transducers in crustaceans. The crustacean hyperglycemic hormone family of peptides regulates various aspects of growth, reproduction, and metabolism. These peptides may function as the terminal hormone to regulate some physiological activities or may function as intermediates in a signaling cascade. Ecdysteroids and terpenoids are two major classes of terminal signaling molecules in these cascades. Hormones from these two classes function independently or in concert to regulate various processes. Ecdysteroid signaling is subject to toxicological disruption through disturbances in ecdysteroid synthesis or binding of toxicants to the ecdysteroid receptor. Methyl farnesoate is the major terpenoid hormone of crustaceans and also is susceptible to disruption by environmental chemicals. However, the methyl farnesoate signaling pathway is poorly understood and only limited mechanistic confirmation for disruption of this endocrine signaling pathway exists. Disruption of the ecdysteroid/terpenoid signaling pathways in crustaceans has been associated with aberrations in growth, metamorphosis, reproductive maturation, sex determination, and sex differentiation. Population studies have revealed disruptions in crustacean growth, molting, sexual development, and recruitment that are indicative of environmental endocrine disruption. However, environmental factors other that pollution (i.e., temperature, parasitism) also can elicit these effects and definitive causal relationships between endocrine disruption in field populations of crustaceans and chemical pollution is generally lacking.

Chironomids: suitable test organisms for risk assessment investigations on the potential endocrine disrupting properties of pesticides

Selecting an appropriate invertebrate assay has been a primary goal of national and international testing programs for endocrine disrupting chemicals. The available information on the endocrine system, its hormones and their modes of action in controlling physiological processes in invertebrates is limited and the selection of appropriate test species still presents a challenge. This paper outlines the development of a higher-tier full life cycle (FLC) test for pesticides with the non-biting midge Chironomus riparius (Insecta, Diptera, Chironomidae). As an insect, C. riparius represents the species' richest and ecologically one of the most important groups of invertebrates. In addition, the endocrine system of insects is one of the best studied among the invertebrates. Acute and chronic tests with Chironomus spp. are commonly used for testing and risk assessment of agrochemicals. A chironomid FLC test protocol has been developed and its suitability investigated in an inter-laboratory comparison. The protocol used is based on existing OECD and US-EPA test methods. To verify the suitability of the test to generate endpoints that encompass adverse effects on the arthropod endocrine system, a juvenile hormone analog was selected as positive control substance. Results have demonstrated that the proposed chironomid FLC can be performed in separate laboratories and that the selected arthropod juvenile hormone mimic causes effects. However, the observed toxicity is not proof of an endocrine disruptive mechanism and could equally be evoked by other compounds. Contrary to a screening assay, which aims at revealing a substance's mode-of-action, the FLC test generates robust, population-relevant endpoints that can be used in the risk assessment of agrochemicals. Since the initial results presented in this paper are encouraging we propose to complete the validation of this assay under OECD with high priority.

Developing Test Guidelines on invertebrate development and reproduction for the assessment of chemicals, including potential endocrine active substances- the OECD perspective

The Organisation for Economic Co-operation and Development (OECD) Test Guidelines Programme is involved in the international harmonization and validation of test methods to evaluate effects of chemicals, including potential endocrine active substances. To meet their existing and foreseen regulatory needs in this area, OECD member countries have encouraged the development of test methods and their emergence at the OECD level. Validation activities are underway in countries and industry to ascertain the relevance and reliability of these tests to enable future regulatory acceptance. This includes work on development and (sexual) reproduction of aquatic invertebrates. What is the importance of mechanistic information in regulating chemicals, and how to address the issue of possible endocrine disruption in invertebrates while integrating these tests in a regulatory scheme are the current questions faced by the OECD countries.

Small is useful in endocrine disrupter assessment--four key recommendations for aquatic invertebrate research

As we enter the 21st "biocentury", with issues such as biodiversity and biotechnology growing in public profile, it is important to reflect on the immense ecological, medical and economic importance of invertebrates. Efforts to understand the diverse biology of invertebrates come from many directions, including Nobel Prize winning developmental biology, research to control insects that threaten human health and food supplies, aquaculture opportunities and also within ecotoxicology. In the latter context, this special journal volume highlights the importance of addressing endocrine disruption in aquatic invertebrates, from molecular and cellular biomarkers to population-relevant adverse effects. The contributors to this special volume have provided an excellent assessment of both the fundamental endocrinology and applied ecotoxicology of many aquatic invertebrate groups. On the premise that reproductive success is ultimately the vital population parameter, this chapter gives a personal view of key gaps in knowledge in invertebrate reproductive and developmental endocrinology and ecotoxicology. Based on current knowledge, there are four key issues that need to be prioritised within aquatic ecotoxicology: (1) a wider assessment of the reproductive status of invertebrates in both freshwater and coastal ecosystems; (2) prioritisation of laboratory studies in OECD and other regulatory test organisms, including basic endocrinology and ADME (absorption, distribution, metabolism and excretion) research; (3) development and validation of mechanistic biomarkers that can be used as "signposts" to help prioritise species and chronic test endpoint selection, and help link data from laboratory and field studies; and (4) develop a comparative invertebrate toxicology database utilising the prioritised reference chemicals from the EDIETA workshop, encompassing the diverse modes-of-action pertinent to endocrine disrupter testing in both aquatic arthropod and non-arthropod invertebrates.