Species Toxicity Tests Research Articles

Modeling the Bioenergetics and Life History Traits of Chironomus riparius–Consequences of Food Limitation

Chironomids have a number of characteristics that make them a useful group for investigating the impact of environmental and chemical stressors on their life cycle stages. It is crucial to first understand sensitivities to environmental factors and provide a basis for interpreting the results of toxicity tests. We focused on Chironomus riparius–one of the most studied species in aquatic toxicity tests—to understand the changes during the larval stage under conditions of food abundance and limitation. We developed a model based on Dynamic Energy Budget (DEB) theory, a framework to capture the entire life cycle of an individual under varying food and temperature conditions. Available information from this study and the literature pointed out that the first three larval instars are immature and the fourth larval instar is mature, during which the organism saves, in two phases, energy for essential processes occurring during the subsequent non-feeding stages. The model can successfully predict the observed prolonged fourth instar duration under food limitation, the times of life history events (e.g., pupation and emergence), and egg production. This model has the potential to be integrated with toxicokinetic–toxicodynamic models to study the effects of toxicants on a variety of biological traits.

Abstract 2373: Functional and specific T-cell engagers against a peptide-MHC tumor target

Abstract Accessing peptides from intracellular tumor antigens displayed on MHC class I (pMHC) can expand the T-cell engager (TCE) target pool for solid tumor applications. A challenge limiting TCE development for pMHC targets is the identification of rare, high-affinity, and high-specificity pMHC-binders. In this work, we describe TCEs in a 1 × 1 format with potent tumor-cell killing activity and high specificity for MAGE-A4, a pMHC tumor antigen expressed in multiple cancer types. We identified functional MAGE-A4 x CD3 TCEs with high specificity and affinity to a human MAGE-A4 peptide sequence of 10 amino acids presented on MHC-I (HLA-A:02*01). We strategically selected MAGE-A4-binders with high binding specificity for pMAGE-A4230-239, but not MHC-I or many closely related MHC-restricted peptides. We then paired them with diverse and developable CD3-binders with a range of binding affinities, subunit specificities, and binding kinetic profiles. High-throughput in vitro functional characterization of hundreds of these TCEs enabled identification of molecules with optimal T-cell dependent cellular cytotoxicity in MAGE-A4-expressing tumor cell lines, with comparable tumor-killing activity and cytokine release to a clinical-stage TCE in a 2 × 1 format. Previous studies have highlighted unique challenges associated with pMHC targets, including their potential for cross-reactive binding to pMHCs on healthy tissues, and the absence of pharmacologically relevant species for preclinical toxicity testing. To address these challenges, we have designed and implemented an in vitro and in silico workflow to identify antibody binding to potential off-target peptides. Using this approach, we selected TCEs with several pMHC binding orientations and high specificity and affinity. These TCEs killed tumor cell lines endogenously expressing MAGE-A4 pMHCs and not isogenic cells with MAGE-A4 knocked out. Results demonstrate that our high-resolution, multiparametric antibody discovery capabilities can identify pMHC-binding antibodies with desired functional and specificity attributes. This approach unlocks the discovery and development of optimal TCEs against complex pMHC antigens. Citation Format: Davide Tortora, Peter Bergqvist, Allison Goodman, Ryan Blackler, Nathalie Blamey, Stefania Carrara, Lauren Chong, Gabrielle Conaghan, Cindy-Lee Crichlow, Valentine de Puyraimond, Harveer Dhupar, Patrick Farber, Jessica Fernandes Scortecci, Kate Gibson, Rodrigo Goya, Ahn Lee, Franco Li, Tova Pinsky, Craig Robb, Patrick Rowe, Antonios Samiotakis, Eduardo Solano Salgado, Ping Xiang, Irene Yu, Kelly Bullock, Tara Fernandez, Stephanie K. Masterman, Kush Dalal, Tim Jacobs, Bryan C. Barnhart. Functional and specific T-cell engagers against a peptide-MHC tumor target [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2373.

Adeno-Associated Virus-Mediated Dorsal Root Ganglion Toxicity in the New Zealand White Rabbit.

Recombinant adeno-associated virus (AAV)-mediated degeneration of sensory neurons in the dorsal root ganglia (DRG) and trigeminal ganglia (TG) has been observed in non-human primates (NHPs) following intravenous (IV) and intrathecal (IT) delivery. Administration of recombinant AAV encoding a human protein transgene via a single intra-cisterna magna (ICM) injection in New Zealand white rabbits resulted in histopathology changes very similar to NHPs: mononuclear cell infiltration, degeneration/necrosis of sensory neurons, and nerve fiber degeneration of sensory tracts in the spinal cord and of multiple nerves. AAV-associated clinical signs and incidence/severity of histologic findings indicated that rabbits were equally or more sensitive than NHPs to sensory neuron damage. Another study using human and rabbit transgene constructs of the same protein demonstrated comparable changes suggesting that the effects are not an immune response to the non-self protein transgene. Rabbit has not been characterized as a species for general toxicity testing of AAV gene therapies, but these studies suggest that it may be an alternative model to investigate mechanisms of AAV-mediated neurotoxicity and test novel AAV designs mitigating these adverse effects.

First report on chemometric modeling of tilapia fish aquatic toxicity to organic chemicals: Toxicity data gap filling

The Toxic Substances Control Act (TSCA) mandates the Environmental Protection Agency (EPA) to document chemicals entering the US. Due to the vast range of toxicity endpoints, experimental toxicological study for all chemicals is impossible to conduct. To address this, in silico methods like QSAR and read-across are strategically used to prioritize testing for chemicals lacking ecotoxicity data. Aquatic toxicity is one of the most critical endpoints directly related to aquatic species, mainly fish, followed by direct to indirect effects on humans through drinking water and fish as food, respectively. Therefore, we have employed the ToxValDB database to curate acute LC50 toxicity data for three Tilapia species covering two different genera, an ideal species for aquatic toxicity testing. Employing the curated dataset, we have developed multiple robust and predictive QSAR and quantitative read-across structure-activity relationship (q-RASAR) models for Tilapia zillii, Oreochromis niloticus, and Oreochromis mossambicus which helped to understand the toxicological mode of action (MoA) of the modeled chemicals and predict the aquatic toxicity of new untested chemicals followed by toxicity data gap filling. The best three QSAR models showed encouraging statistical quality in terms of determination coefficient R2 (0.94, 0.74, and 0.77), cross-validated leave-one-out Q2 (0.90, 0.67 and 0.70), and predictive capability in terms of R2pred (0.95, 0.77, and 0.74) for T. zillii, O. niloticus, and O. mossambicus datasets, respectively. The developed best mathematical models were used for the prediction of aquatic toxicity in terms of pLC50 for 297 untested organic chemicals across three major Tilapia species ranging from 1.841 to 8.561 M in terms of environmental risk assessment.

Phytotoxicity of weathered petroleum hydrocarbons in soil to boreal plant species

Canada has extensive petroleum hydrocarbon (PHC) contamination in northern areas and the boreal forest region from historical oil and gas activities. Since the 2013 standardization of boreal forest species for plant toxicity testing in Canada, there has been a need to build the primary literature of the toxicity of weathered PHCs to these species. A series of toxicity experiments were carried out using fine-grained (<0.005–0.425 mm) background (100 total mg/kg total PHCs) and weathered contaminated soil (11,900 mg/kg total PHCs) collected from a contaminated site in northern Ontario, Canada. The PHC mixture in the contaminated site soil was characterized through Canadian Council of Ministers of the Environment Fractions, as indicated by the number equivalent normal straight-chain hydrocarbons (nC). The soil was highly contaminated with Fraction 2 (>nC10 to nC16) at 4790 mg/kg and Fraction 3 (>nC16 to nC34) at 4960 mg/kg. Five plant species (Elymus trachycaulus, Achillea millefolium, Picea mariana, Salix bebbiana, and Alnus viridis) were grown from seed in 0%, 25%, 50%, 75%, and 100% relative contamination mixtures of the PHC-contaminated and background soil from the site over 2–6 weeks. All five species showed significant inhibition in shoot length, shoot weight, root length, and/or root weight (Kruskal-Wallis Tests: p < 0.05, df = 4.0). Measurements of 25% inhibitory concentrations (IC25) following PHC toxicity experiments revealed that S. bebbiana was most significantly impaired by the PHC-contaminated soil (410–990 mg/kg total PHCs), where it showed <35% germination. This study indicates that natural weathering of Fraction 2- and Fraction 3-concentrated soil did not eliminate phytotoxicity to boreal plant species. Furthermore, it builds on the limited existing literature for toxicity of PHCs on boreal plants and supports site remediation to existing Canadian provincial PHC guidelines.

Adverse Effect of Metallic Gold and Silver Nanoparticles on Xenopus laevis Embryogenesis.

Exposure to metal nanoparticles is potentially harmful, particularly when occurring during embryogenesis. In this study, we tested the effects of commercial AuNPs and AgNPs, widely used in many fields for their features, on the early development of Xenopus laevis, an anuran amphibian key model species in toxicity testing. Through the Frog Embryo Teratogenesis Assay-Xenopus test (FETAX), we ascertained that both nanoparticles did not influence the survival rate but induced morphological anomalies like modifications of head and branchial arch cartilages, depigmentation of the dorsal area, damage to the intestinal brush border, and heart rate alteration. The expression of genes involved in the early pathways of embryo development was also modified. This study suggests that both types of nanoparticles are toxic though nonlethal, thus indicating that their use requires attention and further study to better clarify their activity in animals and, more importantly, in humans.

Considerations regarding the use of nonhuman primates in assessing safety endpoints for pharmaceuticals

Nonhuman primates (NHP) have become a commonly used nonrodent species for general toxicity testing for pharmaceuticals reviewed by CDER. Their increased use in pharmaceutical testing appears to have been driven by both increased use in small molecule drug development programs as well as a trend for biologics making up a greater percentage of pharmaceutical development programs. While always in limited supply, the COVID-19 pandemic acutely impaired the availability of NHPs for pharmaceutical testing due to disruptions in the supply and an increased demand to support COVID-19-directed research programs. Because this disruption in the NHP supply had the potential to significantly delay the development of new medications for the treatment of diseases currently without effective treatment options, FDA issued guidance in February of 2022, under its COVID-19 Public Health Emergency authority, that was intended to help mitigate the NHP supply issue by reducing the demand for NHPs. This guidance has been withdrawn with the expiration of the public health emergency. Here we discuss what impact we expect that the withdrawal of this guidance will have on efforts to minimize NHP use.

Evaluation of the South American gastropod Heleobia parchappii as test organism in cadmium toxicity bioassays

Gastropods are abundant key components in freshwater ecosystems, many of which are affected by anthropogenic activities. The genus Heleobia is widely distributed across Argentina, and the native Heleobia parchappii is very common in the Pampean Region. The identification of native candidate species for toxicity testing is gaining increasing interest. The objectives of the present study were to evaluate 1) the susceptibility of H. parchappii to a reference toxicant (Cl2Cd), and 2) its suitability for toxicity testing by estimating LC50. Also, we discussed the applicability of the proposed protocol. Snail sensitivity was assessed by exposure to concentrations between 0.5 and 12 mg Cd/L under acute static conditions during 72 h (exposure period). Then, snails were transferred to the control medium for 24 h (post-exposure period) and checked for recovery and those not responding to stimulation were considered to be dead. The endpoints were snail immobilization (recorded every 24 h during the exposure period) and mortality at the end of the post-exposure period. Snail sensitivity was analyzed with a generalized linear mixed model (GLMM) and LC50 (lethal concentration 50%) was calculated using probit analysis. Results indicated that the number of immobilized snails increased with increasing concentration. The toxic effect of Cd on snails persisted 24 h after exposure. The LC50 was 2.145 (1.675-2.641) mg Cd/L. The sensitivity of H. parchappii was similar to that reported for other freshwater standard species, supporting its suitability as test organism. The protocol was appropriate for use in toxicity testing as it is simple, inexpensive and reproducible.

Culture Techniques for Acartia clausi from the Romanian Black Sea coastal waters

As copepods are an important food source for most fish larvae, there is a continuing interest in developing techniques for culturing marine copepods as live food in aquaculture. Studies have shown that several species of calanoid copepods can be used successfully in aquaculture, acclimatized and grown in the laboratory over several generations and serve as testing organisms in acute toxicity tests. However, significant difficulties in cultivating calanoid copepods in high quantities were reported. They are related to their low tolerance to changes in water quality and reduced production capacity compared to other taxonomic groups. Therefore, working methods for obtaining viable cultures of calanoid copepods are dependent highly on the local environmental context. Until now, such a method has not been implemented for calanoid species from the Romanian Black Sea coast. This paper details the methodology we adapted and used for achieving a viable Acartia (Acartiura) clausi (Giesbrecht, 1889) culture using specimens collected along the Romania Black Sea coast Reproduction and egg hatching occurred under laboratory-controlled conditions, and viable individuals of A. clausi were obtained. Our results open the possibility of integrating this species in toxicity tests and food production for the marine aquaculture industry.

A Novel Approach to Developing Thresholds for Total Dissolved Solids Using Standardized and Experimental Toxicity Test Methods.

The increasing salinization of freshwater streams from anthropogenic land uses and activities is a growing global environmental problem. Increases in individual ions (such as sodium or chloride) and combined measures such as total dissolved solids (TDS) threaten drinking water supplies, agricultural and economic interests, and the ecological health of freshwater streams. Because the toxicity of high ionic strength waters depends on the specific ion composition, few water quality standards exist to protect freshwater streams from salinization. In the present study, we used a novel approach to develop site-specific and ecologically relevant TDS thresholds for the protection of aquatic life. The first step of the approach was to characterize the ion composition of the waterbody or region of interest and prepare artificial samples to match that composition. Using a combination of standardized toxicity test species and more ecologically relevant field-collected species, toxicity tests were then conducted on these artificial samples prepared at a range of TDS concentrations. The advantage of this approach is that water quality criteria can be developed for easy-to-measure generalized parameters such as TDS while ensuring that the criteria are protective of instream aquatic life and account for the complex interactions of the various ions contributing to salinization. We tested this approach in Sand Branch, Loudoun County, Virginia, USA, where salinization from hard rock mining and urban runoff has impaired aquatic life. Acute and chronic TDS thresholds of 938 and 463 mg/L, respectively, were developed in this stream and used for total maximum daily load development in the watershed. The approach provides a potential model for establishing protective thresholds for other waterbodies impacted by salinization. Environ Toxicol Chem 2022;41:2782-2796. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Stannous chloride as a tool for mercury stripping in contaminated streams: Experimental assessment of toxicity in an invertebrate model species

The chronic toxicity of an innovative Hg water treatment system using tin (Sn) (II) chloride (SnCl2) followed by air stripping was assessed through measurements of survival, growth, and reproduction rate in the freshwater cladoceran Ceriodaphnia dubia, a model species for toxicity testing. We first calculated the concentrations of Hg causing 25% reduction in survival and reproduction (Lethal or Inhibition Concentrations, or LC25 and IC25, for survival and reproduction, respectively) through exposure to aqueous Hg at concentrations ranging from 0 to 25,000 ng L−1. Then, we treated media (DMW and natural stream water) contaminated with Hg at LC25 and IC25 concentrations with SnCl2 at a Sn:Hg stoichiometric ratio of 8:1 and air stripping and exposed C. dubia to this Sn-amended media. Our results showed that Hg significantly affected survival, reproduction rates and impaired growth. SnCl2-treatment removed 100% of the Hg from the media at all concentrations tested with no deleterious effects on survival, growth and reproduction. Our results confirmed the efficacy of SnCl2 in removing aqueous Hg from stream water and showed that the added Sn did not impact C. dubia at the concentrations tested, supporting the suitability of SnCl2-based treatments in appropriate Hg-contaminated environments.

Species selection for nonclinical safety assessment of drug candidates: Examples of current industry practice

In drug development, nonclinical safety assessment is pivotal for human risk assessment and support of clinical development. Selecting the relevant/appropriate animal species for toxicity testing increases the likelihood of detecting potential effects in humans, and although recent regulatory guidelines state the need to justify or dis-qualify animal species for toxicity testing, individual companies have developed decision-processes most appropriate for their molecules, experience and 3Rs policies. These generally revolve around similarity of metabolic profiles between toxicology species/humans and relevant pharmacological activity in at least one species for New Chemical Entities (NCEs), whilst for large molecules (biologics) the key aspect is similarity/presence of the intended human target epitope.To explore current industry practice, a questionnaire was developed to capture relevant information around process, documentation and tools/factors used for species selection. Collated results from 14 companies (Contract Research Organisations and pharmaceutical companies) are presented, along with some case-examples or over-riding principles from individual companies. As the process and justification of species selection is expected to be a topic for continued emphasis, this information could be adapted towards a harmonized approach or best practice for industry consideration.

Estuarine sediment toxicity testing with an indigenous subtropical amphipod

This study reports on a sediment toxicity test developed with a native amphipod strain of Ptilohyale barbicornis where sediments from 10 estuarine stations along the western coastline of Taiwan were evaluated with respect to trace metals and PAHs. The test was validated by determining dose–response relationships for aqueous copper, and cadmium and sodium dodecyl sulfate as well as copper-spiked sediment, showing a sensitivity of P. barbicornis indicating its capability serving as a toxicity test species. A significant negative correlation between growth effects after 28 days of exposure to field-collected contaminated sediments and PAHs concentrations was observed. Similarly, the chronic toxicity test showed that growth was mostly inhibited compared to controls, body lengths in particular being significantly different from controls (p < 0.05). Various estuarine sediment pollutants in the quality guidelines can be further evaluated using P. barbicornis to understand their comprehensive biological effects and ecological risks.

A Novel In Situ Toxicity Identification Evaluation (iTIE) System for Determining which Chemicals Drive Impairments at Contaminated Sites.

Human-dominated waterways contain thousands of chemicals. Determining which chemical is the most important stressor is important, yet very challenging. The Toxicity Identification Evaluation (TIE) procedure from the US Environmental Protection Agency uses a series of chemical and physical manipulations to fractionate compounds within a matrix and systematically identify potential toxicants through laboratory bioassay testing. Although this may provide useful information, it lacks ecological realism because it is subject to laboratory-related artifacts and is resource intensive. The in situ Toxicity Identification Evaluation (iTIE) technology was developed to improve this approach and has undergone a number of modifications over the past several years. The novel prototype 3 consists of an array of iTIE ambient water fractionation units. Each unit is connected to a peristaltic pumping system with an organism exposure chamber that receives water from a resin chamber to chemically fractionate test site water. Test organisms included freshwater and marine standard toxicity test species. Postfractionation waters are collected for subsequent chemical analyses. Currently, the resins allow for separation of ammonia, metals, and nonpolar organics; the subsequent toxicity responses are compared between treatments and unfractionated, ambient exposures. The iTIE system was deployed to a depth of 3 m and evaluated in streams and marine harbors. Chemical analyses of water and iTIE chemical sorptive resins confirmed chemical groups causing lethal to sublethal responses. The system proved to be as sensitive or more so than the traditional phase 1 TIE test and required almost half of the resources to complete. This iTIE prototype provides a robust technology that improves stressor-causality linkages and thereby supports strong evidence for ecological risk weight-of-evidence assessments. Environ Toxicol Chem 2020;39:1746-1754. © 2020 SETAC.

Responses of a tropical micro-crustacean, Daphnia lumholtzi, upon exposures to dissolved toxins and living cells of cyanobacteria

The mass development and expansion of cyanobacteria release cyanotoxins in the aquatic environment and cause serious problems for grazers such as micro-zooplankton. In contrast to aquatic ecosystems in temperate regions, impacts of cyanobacteria and their toxins on tropical micro-crustaceans are relatively understudied. In this study, acute and chronic effects of pure microcystin-LR (MC-LR), a crude extract of water bloom sample with a dominance of Microcystis aeruginosa containing microcystins (MCE) and living cells of Cylindrospermopsis curvispora were tested on a tropical micro-crustacean, Daphnia lumholtzi. The 24 h- and 48 h-LC50 values for MC-LR ranged from 247–299, and 331–409 μg MCE L−1, respectively. Exposures to 1–25 μg MCE L−1 decreased survival, fecundity, and reproduction of D. lumholtzi. The impacts of C. curvispora cells on life-history traits of D. lumholtzi were density-dependent and more severe than the impacts of dissolved microcystins. It could be that the adverse effects of C. curvispora on D. lumholtzi are linked to a combination of potential toxic metabolites, mal-nutrients, feeding and swimming interference. Daphnia lumholtzi used in this study is more sensitive to microcystins compared to Daphnia species from temperate regions. Therefore, we highly suggest using D. lumholtzi as a model species for toxicity testing and monitoring on water quality, particularly in tropical countries.

Development of the transcriptome for a sediment ecotoxicological model species, Chironomus dilutus

Chironomus dilutus is a prominent model species in conventional sediment toxicity testing and sediment contamination diagnosis. However, lack of genomic data significantly limited its application in identifying toxicological mode of action (MOA) and molecular biomarkers of toxicants. Here the transcriptome of C.dilutus in full life span and both sexes (1st, 2nd, 3rd and 4th instar larvae, pupae, and adults) were developed and temporal gene expression across adjacent life stages were investigated to understand the regulation of development. Furthermore, transcriptional response of Midges (the 4th instar larvae) exposed to chemicals of different MOAs (CdCl2, nonylphenol and triclosan) were profiled based on the reference transcriptome. Consequently, a complete transcriptome of 31132 unigenes with N50 of 3117bp, covering 98.8% of the arthropod single-copy orthologs were assembled. While 364 genes were differentially expressed among adjacent larval stages, 7142 and 2127 of transcripts were significantly changed for the transition of larvae-pupae and pupae-adults, respectively. Finally, chemical-specific gene expression profile were identified in the midges, showed its potential in classifying distinct contaminants. Overall, the comprehensive transcriptome of C.dilutus developed here could not only facilitate the mechanistic understanding of environmental toxicants during critical life stage of aquatic insects, but also provide molecular diagnostic tools in sediment ecotoxicology.

Sensitivity of the Marine Calanoid Copepod Pseudodiaptomus pelagicus to Copper, Phenanthrene, and Ammonia.

There are limited acute toxicity test methods for native North American marine species that are considered zooplankton for their entire life cycle. Examples of standardized marine zooplankton methods include mussel, bivalve, and echinoderm development tests that use a relatively short-lived planktonic larval stage, chronic life-cycle toxicity tests using epibenthic copepods, and a 24-h Acartia tonsa copepod test method. The objectives of the present study were to: 1) develop and evaluate a novel, 48-h acute toxicity test method using the marine North American copepod Pseudodiaptomus pelagicus that is planktonic for its entire life cycle, and 2) determine the sensitivity of P. pelagicus relative to commonly tested marine toxicity test species. The average (±1 standard deviation) median lethal concentrations (LC50s) for copper (Cu), phenanthrene, and un-ionized ammonia were 32 ± 15 µg/L, 161 ± 51 µg/L, and 1.08 ± 0.30 mg NH3 /L, respectively. These results placed P. pelagicus on the more sensitive end of Cu and phenanthrene species sensitivity distributions. The copepod was less sensitive to un-ionized ammonia than commonly tested marine species. This finding suggests that the acute P. pelagicus test method will allow a focus on assessing the impacts of persistent contaminants of concern with less confounding impact from naturally occurring ammonia released to the water from sources such as suspended sediments. Environ Toxicol Chem 2019;38:1221-1230. Published 2019 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Physiological sensitivity of Haematococcus pluvialis (Chlorophyta) to environmental pollutants: a comparison with Microcystis wesenbergii (cyanobacteria) and Pseudokirchneriella subcapitata (Chlorophyta)

Haematococcus pluvialis is beneficial to human health and is important for commercial use. However, it seldom prevails in permanent freshwater bodies. Increasing environmental pollutants from anthropogenic activity may threaten the wide distribution of H. pluvialis. Here, we quantified and compared the adverse effects of the common pesticides atrazine, pentachlorophenol, malathion, and 3,5-dichlorophenol and the heavy metals Cu(II), Cr(VI), and Cd(II) on H. pluvialis, Microcystis wesenbergii (a freshwater bloom-forming cyanobacterium), and Pseudokirchneriella subcapitata (a standard toxicity test species). We found that H. pluvialis was the species most sensitive to 3,5-dichlorophenol and Cr(VI) exposure and the most tolerant to pentachlorophenol exposure according to IC50, changes in chlorophyll a content, maximum electron transport rates (ETRmax), the quantum efficiency of photosystem II (Fv/Fm), and esterase activity. Haematococcus pluvialis was also the species most sensitive to atrazine according to IC50, chlorophyll a, and ETRmax. Overall, our findings suggest that atrazine, 3,5-dichlorophenol, and Cr(VI) are potential factors limiting the distribution of H. pluvialis. We suggest that H. pluvialis can be a potentially useful bioindicator for evaluating pollutants. Furthermore, ETRmax, FDA assay, and flow cytometry can be combined with Haematococcus to test for toxicity.

Biodegradation-mediated alterations in acute toxicity of water-accommodated fraction and single crude oil components in cold seawater

Hydrocarbon biodegradation may be slower in cold Arctic than in temperate seawater, and this will affect the toxicity time window of the hydrocarbons. In this study, the acute toxicities of water-soluble phases of 1,3-dimethylnaphthalene, phenanthrene, fluoranthene, and low energy water-accommodated fractions (LE-WAFs) of an evaporated (200 °C+) crude oil, were screened by a Microtox bioassay during biodegradation in cold seawater (4–5 °C). The water-solubility of fluoranthene was too low to provoke a toxic response at any time, whereas the toxicity of 1,3-dimethylnaphthalene and phenanthrene decreased over time in relation to biotransformation of these compounds. In LE-WAFs, the Microtox EC50 was associated with biodegradation of the predominant hydrocarbons (naphthalenes, 2- to 3-ring PAH), as well as with phenol degradation products. The acute toxicities of single hydrocarbons and LE-WAFs persisted for a longer period in the cold seawater than previously shown at higher seawater temperatures. These results suggest implications for fate and effects assessment of hydrocarbons after oil spills in cold environments, like the Arctic. However, further biodegradation studies using Arctic seawater and relevant species for toxicity testing are needed for confirmation.

Is Caenorhabditis elegans representative of freshwater nematode species in toxicity testing?

Multi-species toxicity tests were conducted using a broad range of freshwater nematode species to assess interspecific differences in sensitivity to chemical stress and to compare the toxicity to that on the standard test organism Caenorhabditis elegans. The lethal effects of nine different chemical treatments, including metals and polycyclic aromatic hydrocarbons (PAHs) in single and mixture application, were determined for nematodes exposed for 48h to spiked aqueous solutions. The investigated freshwater nematodes exhibited distinct differences in their sensitivity. Ranking of the susceptibility of 27 species to chemical stress showed that the effects were largely independent of the tested chemical compounds. Overall, the responses of C. elegans were well within the range of those of freshwater nematode species, being slightly less tolerant to metals, but more tolerant to PAHs than the average freshwater species response. Therefore, this study justified the use of C. elegans as representative model for freshwater nematode species in toxicity testing.