Non-chemical stresses do not strongly induce male offspring in Daphnia magna ascertained using the short-term juvenile hormone activity screening assay.

Juvenile hormone (JH), together with ecdysone, regulates molting, metamorphosis, growth, and reproduction in arthropods. The effects of its analogs used as insecticides on nontarget species are of concern. Since JH and JH analogs (JHAs) induce male offspring in daphnids, which generally reproduce by parthenogenesis, short-term JH activity screening assay (JHASA) using the male offspring ratio as an endpoint has been developed as a detection method for JHA.

Prediction of chronic toxicity of pharmaceuticals in Daphnia magna by combining ortholog prediction, pharmacological effects, and quantitative structure-activity relationship.

To develop a method for predicting chronic toxicity of pharmaceuticals in Daphnia, we investigated the feasibility of combining the presence of drug-target orthologs in Daphnia magna, classification based on pharmacological effects, and ecotoxicity quantitative structure-activity relationship (QSAR) prediction. We established datasets on the chronic toxicity of pharmaceuticals in Daphnia, including information on therapeutic categories, target proteins, and the presence or absence of drug-target orthologs in D. magna, using literature and databases.

Developing a Passive Dosing Method for Acute Aquatic Toxicity Tests of Cationic Surfactant Benzalkoniums (BACs).

Benzalkonium chlorides (BACs) have been of environmental concern due to their widespread use and potential harm. However, challenges arise in defining and controlling the exposure concentration () in aquatic toxicity tests involving BACs with a long alkyl chain (i.e.

The complete mitochondrial genome of water flea (Crustacea: Cladocera) NIES strain.

Water flea has been widely used for risk assessments of chemicals and environmental contamination. In this study, the complete mitochondrial genome (mitogenome) of this species NIES strain was determined using short-read high throughput and long-read sequencing technologies. The mitogenome of was 15,170 bp in length and consisted of 13 protein-coding genes (PCGs), 2 ribosomal RNAs (rRNAs), and 22 transfer RNAs (tRNAs).

Influence of water exchange rates on toxicity and bioaccumulation of hydrophobic organic chemicals in sediment toxicity tests.

In standardized sediment toxicity tests, the applied water exchange methods range from static to flow-through conditions and vary between protocols and laboratories even for the same test species. This variation potentially results in variable chemical exposure, hampering the interpretation of toxicity and bioaccumulation. To address these issues, we performed sediment toxicity tests with a mixture of three polycyclic aromatic hydrocarbons (PAHs) and the freshwater epibenthic amphipod as model chemicals and organism, respectively.

Freely dissolved concentration profile and Hyalella azteca toxicity of cationic surfactant C-benzalkonium in spiked-sediment toxicity test.

The freely dissolved concentrations (C) have been considered a useful metric for exposure of aquatic organisms to organic contaminants. However, C for cationic surfactants has rarely been measured, and its use in sediment toxicity tests has not been evaluated. In this study, C of the cationic surfactant benzyldodecyldimethylammonium (C-benzalkonium; C-BAC) in water-only and spiked-sediment toxicity tests with the amphipod Hyalella azteca was analyzed using a passive sampling method.

Comparing 10- and 28-Day Sediment Toxicity and Bioaccumulation of Fluoranthene in Hyalella azteca Using Passive Sampling Techniques.

Understanding the changes in the temporal and spatial concentrations of chemical substances in sediment toxicity tests facilitates interpretation of their toxicity and accumulation in benthic organisms because benthic organisms are affected by chemicals via multiple exposure pathways. However, such investigations using chronic sediment toxicity tests have rarely been performed. To examine the concentration profiles of a hydrophobic organic chemical using chronic spiked-sediment toxicity tests, we performed 28-day sediment toxicity tests of fluoranthene with a freshwater amphipod, Hyalella azteca, using a semi-flow-through system and compared the results with those of 10-day tests.

Severity Classification of Clinical Signs and Defining the Moribund State as an Experimental Endpoint for Acute Toxicity Testing Using Japanese Medaka (Oryzias latipes).

Use of the moribund state as an endpoint for acute toxicity testing in fish is complicated by the lack of consensus about the sublethal signs that define the state or that can predict imminent death. Defining the moribund state in fish requires determination of the association between each observable sublethal sign and transition to imminent death. To establish a criterion for defining the moribund state in Japanese medaka (Oryzias latipes), we determined death/clinical-sign ratios, defined as the proportion of fish with each clinical sign that transitioned to imminent death, for 13 clinical signs observed in individually housed fish exposed to one of two typical toxicants, three pharmaceuticals, two pesticides, and one metal.

Potential differences in chitin synthesis ability cause different sensitivities to diflubenzuron among three strains of Daphnia magna.

Ecotoxicity testing of crustaceans using Daphnia magna has been implemented in the chemical management systems of various countries. While the chemical sensitivity of D. magna varies depending on genetically different clonal lineages, the strain used in ecotoxicity tests, including the acute immobilization test (OECD TG202), has not been specified.

Juvenile hormone synthesis and signaling disruption triggering male offspring induction and population decline in cladocerans (water flea): Review and adverse outcome pathway development.

Juvenile hormone (JH) are a family of multifunctional hormones regulating larval development, molting, metamorphosis, reproduction, and phenotypic plasticity in arthropods. Based on its importance in arthropod life histories, many insect growth regulators (IGRs) mimicking JH have been designed to control harmful insects in agriculture and aquaculture. These JH analogs (JHAs) may also pose hazards to nontarget species by causing unexpected endocrine-disrupting (ED) effects such as molting and metamorphosis defects, larval lethality, and disruption of the sexual identity.

Comparison of Species Sensitivity Distributions for Sediment-Associated Nonionic Organic Chemicals Through Equilibrium Partitioning Theory and Spiked-Sediment Toxicity Tests with Invertebrates.

Equilibrium partitioning (EqP) theory and spiked-sediment toxicity tests are useful methods to develop sediment quality benchmarks. However, neither approach has been directly compared based on species sensitivity distributions (SSDs) to date. In the present study, we compared SSDs for 10 nonionic hydrophobic chemicals (e.

Summary of 17 chemicals evaluated by OECD TG229 using Japanese Medaka, Oryzias latipes in EXTEND 2016.

In June 2016, the Ministry of the Environment of Japan announced a program "EXTEND2016" on the implementation of testing and assessment for endocrine active chemicals, consisting of a two-tiered strategy. The aim of the Tier 1 screening and the Tier 2 testing is to identify the impacts on the endocrine system and to characterize the adverse effects to aquatic animals by endocrine disrupting chemicals detected in the aquatic environment in Japan. For the consistent assessment of the effects on reproduction associated with estrogenic, anti-estrogenic, androgenic, and/or anti-androgenic activities of chemicals throughout Tier 1 screening to Tier 2 testing, a unified test species, Japanese medaka (Oryzias latipes), has been used.

Spatiotemporal Distribution of Hydrophobic Organic Contaminants in Spiked-Sediment Toxicity Tests: Measuring Total and Freely Dissolved Concentrations in Porewater and Overlying Water.

The sediment-water interface of spiked-sediment toxicity tests is a complex exposure system, where multiple uptake pathways exist for benthic organisms. The freely dissolved concentration (C ) in sediment porewater has been proposed as a relevant exposure metric to hydrophobic organic contaminants (HOCs) in this system. However, C has rarely been measured in spiked-sediment toxicity tests.

Dying for change: A roadmap to refine the fish acute toxicity test after 40 years of applying a lethal endpoint.

The fish acute toxicity test (TG203; OECD, 2019) is frequently used and highly embedded in hazard and risk assessment globally. The test estimates the concentration of a chemical that kills 50% of the fish (LC) over a 96 h exposure and is considered one of the most severe scientific procedures undertaken. Over the years, discussions at the Organisation for Economic Co-operation and Development (OECD) have resulted in changes to the test which reduce the number of fish used, as well as the development of a (potential) replacement test (TG236, OECD, 2013).

Toxicity assessment of typical polycyclic aromatic hydrocarbons to Daphnia magna and Hyalella azteca in water-only and sediment-water exposure systems.

While the equilibrium partitioning (EqP) method has been demonstrated to effectively predict the adverse effects of nonionic organic chemicals in sediment on benthic organisms by sediment toxicity tests, only a limited number of studies have been performed both in water-only and whole-sediment toxicity tests using the same species and verified the validity of EqP-based toxicity assessment. To further examine the validity of the EqP method for application in a wide range of hydrophobicity, we conducted sorption/desorption experiments and both water-only and sediment toxicity tests using a popular aquatic crustacean species, Daphnia magna (48 h), and benthic species Hyalella azteca (96 h) for six typical polycyclic aromatic hydrocarbons (PAHs) with three to five rings and an amine derivative: anthracene, phenanthrene, fluoranthene, pyrene, benzo[a]pyrene, dibenzo[a,h]anthracene, and 1-aminopyrene. The linear sorption coefficient was determined and ranged from 2.

Sources of variation in sediment toxicity of hydrophobic organic chemicals: Meta-analysis of 10-14-day spiked-sediment tests with Hyalella azteca and Chironomus dilutus.

Spiked-sediment toxicity tests with benthic organisms are routinely used to assess the potential ecological impact of sediment-associated hydrophobic organic contaminants. Although several sediment tests have been standardized, experimental factors such as spiking methods still vary between laboratories. To identify the experimental factors that affect the bioavailability of contaminants and account for the highest percentage of the variability of toxicity values (i.

Detection of feline norovirus using commercial real-time RT-PCR kit for the diagnosis of human norovirus infection.

Feline noroviruses (FNoVs) are potential clinical pathogens in cats. To perform an epidemiological study of FNoV infection, it is necessary to develop a simple and effective method for virus detection. We investigated whether a commercial human NoV quantitative RT-PCR kit for the detection of human NoVs used in medical practice can be applied for FNoV detection.

Summary of reference chemicals evaluated by the fish short-term reproduction assay, OECD TG229, using Japanese Medaka, Oryzias latipes.

Under the Organisation for Economic Co-operation and Development (OECD), the Ministry of the Environment of Japan (MOE) added Japanese medaka (Oryzias latipes) to the test guideline fish short-term reproduction assay (FSTRA) developed by the United States Environmental Protection Agency (US EPA) using fathead minnow (Pimephales promelas). The FSTRA was designed to detect endocrine disrupting effects of chemicals interacting with the hypothalamic-pituitary-gonadal axis (HPG axis) such as agonists or antagonists on the estrogen receptor (Esr) and/or the androgen receptor (AR) and steroidogenesis inhibitors. We conducted the FSTRA with Japanese medaka, in accordance with OECD test guideline number 229 (TG229), for 16 chemicals including four Esr agonists, two Esr antagonists, three AR agonists, two AR antagonists, two steroidogenesis inhibitors, two progesterone receptor agonists, and a negative substance, and evaluated the usability and the validity of the FSTRA (TG229) protocol.

Production of genome-edited Daphnia for heavy metal detection by fluorescence.

Aquatic heavy metal pollution is a growing concern. To facilitate heavy metal monitoring in water, we developed transgenic Daphnia that are highly sensitive to heavy metals and respond to them rapidly. Metallothionein A, which was a metal response gene, and its promoter region was obtained from Daphnia magna.

Deep convolutional neural network-based anomaly detection for organ classification in gastric X-ray examination.

Aim: The aim of this study was to determine whether our deep convolutional neural network-based anomaly detection model can distinguish differences in esophagus images and stomach images obtained from gastric X-ray examinations.

Methods: A total of 6012 subjects were analyzed as our study subjects. Since the number of esophagus X-ray images is much smaller than the number of gastric X-ray images taken in X-ray examinations, we took an anomaly detection approach to realize the task of organ classification.

Whole transcriptome analysis of an estuarine amphipod exposed to highway road dust.

Urban road dust can potentially have adverse effects on aquatic and benthic ecosystems if discharged into receiving waters; however, little is known about the mode of action of road dust toxicity within aquatic organisms. With an aim to reveal the biological effects of road dust on benthic crustacean species, we performed a de novo transcriptome analysis of the estuarine amphipod Grandidierella japonica exposed to road dust collected from highways around Tokyo. A transcriptome analysis by Illumina HiSeq 2500 identified differentially expressed genes related to the gamma-aminobutyric acid (GABA) signaling pathway, oxidative damage, and cuticle metabolism.

Estimation of population-level effect of the endocrine disruptor pyriproxyfen in Daphnia magna by using changes in sex ratio and reproductive output.

Here we developed an analytical means of estimating population-level effects of endocrine disruptors on Daphnia magna. Our approach was based on the fact that the endocrine-disrupting juvenile hormone analogs induce the production of male neonates if they are exposed to the analogs during a particular period in their prenatal development; the method also assumed that the abnormal production of male neonates in the sake of production of female neonates reduces population growth. We constructed a linear toxicodynamics model to elucidate the period in which D.

Comparison of the effects of constant and pulsed exposure with equivalent time-weighted average concentrations of the juvenile hormone analog pyriproxyfen on the reproduction of Daphnia magna.

Short-term pulsed exposure tests have been increasingly used to evaluate the ecotoxicity of pollutants of which concentrations vary over time in the field. In pulsed exposure, time-weighted average (TWA) concentration is often used as an index of exposure. However, there have been few studies to demonstrate whether TWA concentration can be used to evaluate the effect of endocrine-disrupting chemicals on the daphnids.

Effects of triphenyltin on reproduction in Japanese medaka (Oryzias latipes) across two generations.

Triphenyltin (TPT) is an organotin compound used in marine anti-fouling coatings to prevent the attachment and growth of marine organisms, and it has negative effects on aquatic organisms. TPT is still detected at low concentrations, although its use has been prohibited at least in the European Community and is restricted in Japan as well. Studies using Japanese medaka (Oryzias latipes) indicate that TPT has the potential to inhibit reproduction.

Medaka extended one-generation reproduction test evaluating 4-nonylphenol.

The medaka extended one-generation test (MEOGRT) was developed as a multigenerational toxicity test for chemicals, particularly endocrine-disrupting chemicals. Briefly, 3 generations of Japanese medaka (Oryzias latipes) are exposed to a chemical over a 20-wk period: 3 wk in the parental generation (F0), 15 wk in the first generation (F1), and 2 wk in the second generation (F2). The present study reports the first MEOGRT results concerning branched isomer mixtures of 4-nonylphenol (NP).