Effects of nanomolar methylmercury on developing human neural stem cells and zebrafish Embryo.

Exposure to mercury and its organic form methylmercury (MeHg), is of great concern for the developing nervous system. Despite available literature on MeHg neurotoxicity, there is still uncertainty about its mechanisms of action and the doses that trigger developmental effects. Our study combines two alternative methodologies, the human neural stem cells (NSC) and the zebrafish (ZF) embryo, to address the neurotoxic effects of early exposure to nanomolar concentrations of MeHg. Our results show linear or nonmonotonic (hormetic) responses depending on studied parameters. In ZF, we observed a hormetic response in locomotion and larval rotation, but a concentration-dependent response for sensory organ size and habituation. We also observed a possible delayed response as MeHg had greater effects on larval activity at 5 days than at 24 h. In NSC cells, some parameters show a clear dose dependence, such as increased apoptosis and differentiation to glial cells or decreased neuronal precursors; while others show a hormetic response: neuronal differentiation or cell proliferation. This study shows that the ZF model was more susceptible than NSC to MeHg neurotoxicity. The combination of different models has improved the understanding of the underlying mechanisms of toxicity and possible compensatory mechanisms at the cellular and organismal level.

Embryonic toxicity of Imidacloprid: Impact on hatchability, survivability, swimming speed and cardiac function of catfish, Clarias gariepinus.

Imidacloprid is a systemic insecticide that belongs to the neonicotinoid class of chemicals that act on the central nervous system of insects. Imidacloprid is used to control sucking insects, chewing insects such as termites, soil insects, and fleas on pets, as well as to treat structures, crops, soil, and seeds. As a result of these factors, this pesticide may end up in the aquatic environment via municipal discharges and runoff. Although the presence of imidacloprid in aquatic environments has been underreported as widespread, the toxic effects of this pesticide may have serious implications on aquatic organisms, particularly at environmentally relevant concentrations and demand more attention. Given this knowledge, the goal of this study was to investigate the effects of imidacloprid on Clarias gariepinus embryonic development. Clarias gariepinus embryos (3 h post-fertilization) were exposed to environmentally relevant concentrations of imidacloprid (10, 30, 100, and 500 µg/L) until 48 h post-fertilization using a modified fish embryo acute toxicity test (OECD TG 236). A stereomicroscope was used to assess hatchability, deformity, heart rate, and swimming speed as endpoints. According to our results of the developmental acute toxicity test, imidacloprid significantly reduced the hatching rate and heartbeats of C. gariepinus embryos. It also influenced the swimming kinematics of exposed embryos and caused teratogenic effects such as yolk sac rupture, pericardial oedema, lordosis, an abnormally shaped head, and altered epiboly. Our results allow us to conclude that imidacloprid is a toxic pesticide in the early life stages of C. gariepinus due to its high teratogenic potential.

The impact of co-treatment with graphene oxide and metal mixture on Salmo trutta at early development stages: The sorption capacity and potential toxicity.

Graphene oxide (GO) are novel nanomaterials with a wide range of applications due to their high absorption capacity. This study was undertaken with a view to assess the bioaccumulation and acute toxicity of GO used in combination with the heavy metal mixture (Cr, Cu, Ni and Zn) to fish embryos and larvae. For this purpose, Salmo trutta embryos and larvae were subjected to the 4-day long treatment with three different concentrations of GO, the metal mixture, which was prepared of four metals at the concentrations corresponding to the maximum-permissible-concentrations for EU inland waters (Cr-0.01, Cu-0.01, Ni-0.034, and Zn-0.1 mg/L), and with GO in combination with MIX (GO+MIX). When used in combination with the metal mixture, GO exhibited a high metal sorption capacity. The obtained confocal fluorescence microscopy results showed that GO located in the embryo chorion causing its damage; in larvae, however, GO were found only in the gill region. Results of these experiments confirmed the hypothesis that GO affects the accumulation of metals and mitigates their toxic effects on organism. In embryos, the acute toxicity of exposure to GO and co-exposure to MIX+GO was found to manifest itself through the decreased heart rate (HR) and malondialdehyde (MDA) level and through the increased metallothionein (MT) concentration. Meanwhile, in larvae, GO and MIX+GO were found to induce genotoxicity effects. However, changes in HR, MDA, MT, gill ventilation frequency, yolk sack absorption and cytotoxicity compared with those of the control group were not recorded in larvae. The obtained results confirmed our hypothesis: the combined effect of MIX and GO was less toxic to larvae (especially survival) than individual effects of MIX components. However, our results emphasize that fish exposure to GO alone and in combination with heavy metal contaminants (MIX+GO) even at environmentally relevant concentrations causes health risks that cannot be ignored.

In Vitro and In Vivo Toxicity Evaluation of Natural Products with Potential Applications as Biopesticides.

The use of natural products in agriculture as pesticides has been strongly advocated. However, it is necessary to assess their toxicity to ensure their safe use. In the present study, mammalian cell lines and fish models of the zebrafish (Danio rerio) and medaka (Oryzias latipes) have been used to investigate the toxic effects of ten natural products which have potential applications as biopesticides. The fungal metabolites cavoxin, epi-epoformin, papyracillic acid, seiridin and sphaeropsidone, together with the plant compounds inuloxins A and C and ungeremine, showed no toxic effects in mammalian cells and zebrafish embryos. Conversely, cyclopaldic and α-costic acids, produced by Seiridium cupressi and Dittrichia viscosa, respectively, caused significant mortality in zebrafish and medaka embryos as a result of yolk coagulation. However, both compounds showed little effect in zebrafish or mammalian cell lines in culture, thus highlighting the importance of the fish embryotoxicity test in the assessment of environmental impact. Given the embryotoxicity of α-costic acid and cyclopaldic acid, their use as biopesticides is not recommended. Further ecotoxicological studies are needed to evaluate the potential applications of the other compounds.

Sublethal toxicity of PbI2 in perovskite solar cells to fish embryos (Danio rerio and Oryzias latipes): Deformity and growth inhibition.

Pb-based perovskite in solar cells is a source of PbI2. The objective of this study was to characterize the embryonic toxicity of PbI2, a potentially leachable chemical and hazardous material, for two fish species (zebrafish and Japanese medaka). A series of measurements were performed to assess mortality, abnormalities (deformities and other pathological changes), hatchability, and growth inhibition. The results obtained showed that the toxicities observed were predominantly associated with Pb2+ and I-. Therefore, given the potential ecotoxicity of PbI2, precautions should be taken to prevent its release during the breakage and disposal of Pb-based perovskite solar cells.

Developmental neurotoxicity fingerprint of silica nanoparticles at environmentally relevant level on larval zebrafish using a neurobehavioral-phenomics-based biological warning method.

BACKGROUND: Larval zebrafish (Danio rerio) is not only an ideal vertebrate applied in Fish Embryos Toxicity (FET) test but also a well-accepted model in behavioral neurotoxicity research. By applying the commercial standard behavioral tracking system (Zebrabox), the locomotion profiles (neurobehavioral-phenomics) of larval zebrafish can be comprehensively monitored and systematically analyzed to probe ecotoxicological neurotoxicity of nano-pollutants at environmental relevant concentration level. RESULTS: Herein, the potential toxicity of at environment relevant concentration level on embryonic zebrafish was evaluated by FET and neurobehavioral-phenomics (NBP). The embryos were exposed to the environmental relevant concentration (0.05, 0.1,1, 5, 10, 100 µg/L). The FET criteria were utilized to evaluate the ecotoxicological effect induced by silica NPs. Subsequently, behavioral neurotoxicity of silica NPs was further quantified via locomotion response (LMR). Specifically, the alteration of Light/Dark challenge (LDC) evoked by light/dark stimulation was detected and analyzed by commercially standard behavioral protocols using zebrabox. We revealed that the exposures of silica NPs at environmental relevant concentration (0.05, 0.1, 1, 5, 10,100 µg/L) significantly disturbed locomotion profiles of larval zebrafish. Additionally, it was obviously noted that low, environmentally relevant silica concentrations might result in altering the total behavioral profiles in developing zebrafish. CONCLUSIONS: In sum, neurobehavior phenomics profiling based on LMR and LDC is a potent methodology for the evaluation of sub-lethal or sub-teratogenic toxicity. Compared with the FET tests characterized by the detection of embryonic teratogenicity, the neurobehavior phenomics based method can be more sensitive to determine sub-teratogenic toxicity of silica NPs at environmental concentrations. With the combination of multivariate data analysis, this approach would offer effective technical reference for environmental nano-toxicology research.

Effects of chronic exposure to microplastics of different polymer types on early life stages of sea trout Salmo trutta.

The aim of the present study was to determine the effect of a long-term (113 days) exposure to microplastics on the development and induction of endocrine, geno- and cytotoxic responses in early life stages of sea trout Salmo trutta. Microplastic particles (3000 µm) of three most commonly mass-produced polymers (polystyrene - PS, polyethylene terephthalate - PET and polyethylene - PE) were applied in environmentally realistic concentrations (0.1% of sediment dry weight) in a laboratory experiment imitating the natural environment, typical for sea trout spawning grounds. The exposure of the sea trout, from fertilized eggs to mobile yolk-sac larvae, to microplastics did not affect the hatching success (the survival of embryos), hatching rate and the incubation period. Microplastics of any tested polymer type also had no adverse effect on the larvae survival, growth rate and the rate of yolk sack absorption. Similarly, no changes in frequencies of detected cytotoxicity endpoints compared to the control group were recorded. Exposure to polymer particles induced however the formation of genotoxicity endpoints (nuclear buds, micronuclei and blebbed nuclei cells). The level of total genotoxicity (ΣGentox) in fish larvae erythrocytes increased significantly in the following sequence: PS > PET > PE. No significant changes in the whole body corticosterone, dehydrocorticosterone and cortisone concentrations due to exposure to microplastics were recorded, while cortisol was detected in larvae exposed to PS. Our results show that long-term, non-ingestion related exposure to microplastics does not affect development of S. trutta early life stages but may lead to genotoxic responses. PS seems to be the most hazardous among all polymers studied. This is the first study demonstrating non-ingestion related toxicity of microplastics to the early life stages of fish.

Comprehensive Toxicity Assessment of PEGylated Magnetic Nanoparticles for in vivo applications.

Magnetic nanoparticles (MNPs) represent one of the greatest promises for the development of a new generation of diagnostic agents for magnetic resonance imaging, with improved specificity and safety. Indeed, during the last decade the number of studies published in this field has grown exponentially. However, the clinical translation achieved so far has been very limited. This situation is likely related to the fact that most studies are focused on the in vitro characterization of these new nanomaterials, and very few provide an exhaustive in vivo characterization, where key aspects, such as pharmacokinetics, bioavailability, and, most importantly, toxicity, are properly evaluated. In this work, we propose a protocol for the comprehensive assessment of the toxicity of MNPs, based on the use of zebrafish embryos as an intermediate screening step between cell culture assays and studies in rodents. MNPs with different cores, ferrite and manganese ferrite oxide, and sizes between 3 and 20 nm, were evaluated. Cell viability at a concentration of 50 µg/mL of PEGylated MNPs was above 90 % in all cases. However, the exposure of zebrafish embryos to manganese based MNPs at concentrations above 100 µg/mL showed a low survival rate (<50 %). In contrast, no mortality (survival rate ∼100 %) and normal hatching rate were obtained for the iron oxide MNPs. Based on these results, together with the physicochemical and magnetic properties (r2 = 153.6 mM-1·s-1), the PEGylated 20 nm cubic shape iron oxide MNPs were selected and tested in mice, showing very good MRI contrast and, as expected, absence of toxicity.

Interaction of carboxylated CdSe/ZnS quantum dots with fish embryos: Towards understanding of nanoparticles toxicity.

Due to colloidal instability even with protective coatings, nanoparticles tend to aggregate in complex environments and possibly interact with biota. In this study, visualization of quantum dots (QDs) interaction with rainbow trout (Oncorhynchus mykiss) embryos was performed. Studies on zebrafish (Danio rerio) and pearl gourami (Trichogaster leerii) embryos have shown that QDs interact with embryos in a general manner and their affects are independent on the type of the embryo. It was demonstrated that carboxylated CdSe/ZnS QDs (4 nM) were aggregating in accumulation media and formed agglomerates on the surface of fish embryos under 1-12 days incubation in deep-well water. Detailed analysis of QDs distribution on fish embryos surface and investigation of the penetration of QDs through embryo's membrane showed that the chorion protects embryos from the penetration through the chorion and the accumulation of nanoparticles inside the embryos. Confocal microscopy and spectroscopy studies on rainbow trout embryos demonstrated that QDs cause chorion damage, due to QDs aggregation on the surface of chorion, even the formation of the agglomerates at the outer part of the embryos and/or with the mucus were detected. Aggregation of QDs and formation of agglomerates on the outer part of the embryo's membrane caused the intervention of the aggregates to the chorion and even partially destroyed the embryo's chorion. The incorporation of QDs in chorion was confirmed by two methods: in living embryos from a 3D reconstruction view, and in slices of embryos from a histology view. The damage of chorion integrity might have adverse effects on embryonic development. Moreover, for the first time the toxic effect of QDs was separated from the heavy metal toxicity, which is most commonly discussed in the literature to the toxicity of the QDs.

The sugarcane herbicide ametryn induces oxidative stress and developmental abnormalities in zebrafish embryos.

Ametryn (AMT) is one of the most widely used herbicides in tropical sugarcane crops, the main culture of São Paulo State, Brazil. It is known as a diffuse pollutant, being found in surface water and sediment of water bodies adjacent to the crop fields. In the present study, the toxicity of AMT to zebrafish (Danio rerio) embryos was evaluated using developmental and biochemical endpoints. At the biochemical level, lactate dehydrogenase responded at the lowest concentration tested (4 µg L-1) indicating a high demand of energy required to cope with the stress condition. Antioxidant enzyme levels were changed at intermediate/high concentrations while oxidative damage (lipid peroxidation) was observed at the last concentration tested (10 mg L-1). This suggests that, like for other herbicides from the triazine group, oxidative stress is a major pathway of toxicity for AMT. Several developmental effects such as oedemas and tail deformities were also observed. The 96 h-EC50 values calculated for different developmental parameters were between 17 and 29 mg L-1. AMT also affected hatching (96 h-EC50 = 22.5 mg L-1) and positioning in the water column (96 h-EC50 = 13.2 mg L-1). In a previous work of the group, lethal toxicity of AMT showed to be much higher to adults than to embryos. However, in the present work, sublethal endpoints assessed suggest that important effects are observed at lower concentrations, improving the sensitivity of the embryo test. Moreover, in this work, sublethal effects were observed for concentrations in the same range as the ones found in the environment, and thus, given that this chemical is widely used in tropical fields, a refined evaluation of risk should be performed based on the monitoring of sublethal and long-term parameters and considering mixture scenarios.

Post-cooling survival, growth and deformity rates in zebrafish embryos (Danio rerio).

This study investigated and analysed survival, growth and macro- and microscopic damage during the development of zebrafish embryos up to the adult stage after undergoing cooling. The embryos at 50% epiboly stage were selected, submerged in cryoprotectant solution of methanol and sucrose, cooled gradually to 0 ± 2°C temperature, and divided into two groups with different storage times (6 and 18 h). Subsequently, the embryos were reheated, rehydrated and incubated normally. The experiment lasted 5 months and, from hatching onward, the larvae were examined, collected and processed at pre-established time intervals. The hatching rate was significantly higher for the larvae stored for 18 h compared with the 6-h group. However, embryos from this group gave rise to a larger number of malformations, and these were much more severe compared with those in the 6 h group, which led to a higher mortality in the long term. Regarding larval length, the animals of the 6 h group had higher mean total length compared with the 18 h group, but both treatments were inferior to the control. Numerous macro- and microscopic malformations were observed and, in both treatments, only the morphologically normal individuals were able to develop to the adult stage, with organ development similar to the control, except for the gonads that were still undifferentiated in treated animals.

Correlation between LC50 for Adult Fish and Fish Embryos.

Testing for substance toxicity for living organisms is an important step in the development and adaptation of new drugs for various purposes. Analysis of the dependences between toxicological parameters of chemical substances for various test objects and physicochemical properties of these agents is a promising trend. Partition coefficient logP (logKow) was chosen as the key physicochemical parameter determining the toxicological parameters of the same substance for hydrobionts at different developmental stages. We found a correlation between decimal logarithm of the ratio of LCe50 for fish embryos to LCa50 for adult fish and logP. This dependence was found as a liner combination of equations obtained by drawing a trend line between experimental points and calculation of Pearson's correlation coefficient R.

Exploring uptake and biodistribution of polystyrene (nano)particles in zebrafish embryos at different developmental stages.

In ecotoxicology, it is continuously questioned whether (nano)particle exposure results in particle uptake and subsequent biodistribution or if particles adsorb to the epithelial layer only. To contribute to answering this question, we investigated different uptake routes in zebrafish embryos and how they affect particle uptake into organs and within whole organisms. This is addressed by exposing three different life stages of the zebrafish embryo in order to cover the following exposure routes: via chorion and dermal exposure; dermal exposure; oral and dermal exposure. How different nanoparticle sizes affect uptake routes was assessed by using polystyrene particles of 25, 50, 250 and 700nm. In our experimental study, we showed that particle uptake in biota is restricted to oral exposure, whereas the dermal route resulted in adsorption to the epidermis and gills only. Ingestion followed by biodistribution was observed for the tested particles of 25 and 50nm. The particles spread through the body and eventually accumulated in specific organs and tissues such as the eyes. Particles larger than 50nm were predominantly adsorbed onto the intestinal tract and outer epidermis of zebrafish embryos. Embryos exposed to particles via both epidermis and intestine showed highest uptake and eventually accumulated particles in the eye, whereas uptake of particles via the chorion and epidermis resulted in marginal uptake. Organ uptake and internal distribution should be monitored more closely to provide more in depth information of the toxicity of particles.

Effect of Pelargonidin isolated from Ficus benghalensis L. on phenotypic changes in zebrafish (Danio rerio) embryos.

In the present study, the extraction and isolation of Pelargonidin, an anthocyanin compound from stem bark of Ficus benghalensis are described. The study also involves evaluation of the effect of Pelargonidin on phenotypic variations in zebra fish embryos. Extraction and isolation of Pelargonidin were carried out by employing liquid-liquid extraction technique, phytochemical tests, column chromatography, UV and FT-IR. In the zebra fish embryo model, Paclitaxel was employed as a negative control. A series of phenotypic changes in different stages of embryonic development were studied with treatment concentrations of Pelargonidin between 3.0 and 20 ppm at 0-72-hour post-fertilization (hpf). The results of our studies indicate that, after exposure of zebra fish embryos to 3.3-20 ppm concentration of Pelargonidin for 72 h, a significant reduction in aortic development occurs. At the dose level of 0.5 ppm Paclitaxel and Pelargonidin in the dose range between 3.3 and 20 ppm, the zebra fish embryos were found to have bent tail, malformed eyes and developmental delays in vasculature. Based on the results obtained, we infer that Pelargonidin can exhibit phenotypic anti-angiogenic variations in embryonic stage of fish embryos and it can be applied in future for exploration of its anti-angiogenic potential. Furthermore, Pelargonidin could serve as a candidate drug for in vivo inhibition of angiogenesis and can be applied for the treatment of neovascular diseases and tumor.

Dependence between LD50 for Rodents and LC50 for Adult Fish and Fish Embryos.

We revealed empirical dependences between common logarithm of a ratio of rat oral LD50 to LCa50 for adult fish and lgP for 50 different chemicals; and common logarithm of a ratio of the oral LD50 in rodents to LCe50 for fish embryos and lgP for 30 different chemicals. The dependences were obtained by constructing a trend line between experimental points and calculation of Pearson's R correlation coefficient as a measure of regression significance. These dependences can show the influence of substance lipophilicity on its toxicity for aquatic organisms comparing to mammals.

RNA seq- and DEG-based comparison of developmental toxicity in fish embryos of two species exposed to Iranian heavy crude oil.

To determine and compare the toxic effects of Iranian heavy crude oil (IHCO) on the embryonic development of two fish species, we examined transcriptome profiles using RNA-seq. The assembled contigs were 66,070 unigenes in olive flounder embryos and 76,498 unigenes in spotted seabass embryos. In the differential gene expression (DEG) profiles, olive flounder embryos showed different up- and down-regulated patterns than spotted seabass embryos in response to fresh IHCO (FIHCO) and weathered IHCO (WIHCO). In this work, we categorized DEG profiles into six pathways: ribosome, oxidative phosphorylation, Parkinson's disease, Alzheimer's disease, Huntington's disease, and cardiac muscle contraction, validating the expression patterns of 13 DEGs using real-time quantitative RT-PCR. The expression of the CYP1A, CYP1B1, and CYP1C1 genes in spotted seabass embryos was higher than in olive flounder embryos, whereas genes related to cell processing, development, and the immune system showed the opposite trend. Orthologous gene cluster analysis showed that olive flounder embryos were sensitive (fold change of genes with cutoff P<0.05) to both FIHCO and WIHCO, but spotted seabass embryos exhibited higher sensitivity to WIHCO than FIHCO, indicating that species-specific differences are likely to be reflected in population levels after oil spills. Overall, our study provides new insight on the different embryonic susceptibilities of two marine fish species to FIHCO and WIHCO and a better understanding of the underlying molecular mechanisms via RNA-seq and DEGs.

The toxicity of creosote-treated wood to Pacific herring embryos and characterization of polycyclic aromatic hydrocarbons near creosoted pilings in Juneau, Alaska.

Polycyclic aromatic hydrocarbons (PAHs) from creosote exposure in the laboratory resulted in deleterious effects in developing Pacific herring (Clupea pallasi) embryos, and potentially toxic concentrations of PAHs were measured using passive water samplers at 1 of 3 harbor field sites in Juneau, Alaska, USA. Aqueous total PAH concentrations of 4.6 µg/L and 8.4 µg/L from creosote exposure resulted in skeletal defects and ineffective swimming in hatched larvae in the laboratory (10% effective concentrations) and were the most sensitive parameters measured. Hatch rates also suffered from creosote exposure in a dose-dependent manner: at exposures between 5 µg/L and 50 µg/L total PAH, 50% of the population failed to hatch. Comparisons between laboratory and field deployed passive samplers suggested that for at least 1 harbor in Juneau, concentrations sufficient to induce teratogenic effects were found directly on creosoted pilings, within 10 cm of them, and sometimes at a distance of 10 m. Total PAH concentrations generally decreased with distance from creosoted pilings. Creosote pilings contribute to the PAH load within a marina and can rise to PAH concentrations that are harmful to fish embryos, but at a scale that is localized in the environment. Environ Toxicol Chem 2017;36:1261-1269. © 2016 SETAC.

Molecular and phenotypic responses of Japanese medaka (Oryzias latipes) early life stages to environmental concentrations of cadmium in sediment.

Japanese medaka embryos were exposed to environmental concentrations of cadmium (Cd) to investigate adverse and adaptive responses in fish early life stages. Embryos were exposed during their whole development by static sediment-contact to environmental Cd concentrations (2 and 20 µg/g dry weight). Cd bioaccumulation, developmental defects, biochemical and biomolecular (qRT-PCR) responses were analyzed in embryos and hatchlings. A dose-dependent increase of Cd bioaccumulation and developmental defects was observed at hatching. Cd had clear impacts on heartbeat and cardiac morphogenesis and also induced to spinal deformities. The profile and the level of gene transcription were differentially modulated according to the Cd concentration, the duration of exposure and/or the developmental stage of fish. Pro-apoptotic bax and DNA repair rad51 transcripts were significantly repressed in embryos exposed to the highest Cd concentration. Repression of these genes was correlated to the increase of heart rate in 6-day-old embryos. NADH-dehydrogenase nd5 gene transcription was inhibited in larvae at the lowest concentration suggesting mitochondrial respiratory chain impairment, in association with Cd-induced teratogenicity. Finally, wnt1 gene was overexpressed indicating putative deregulation of Wnt signaling pathway, and suggested to be implied in the occurrence of some spinal and cardiac deformities. Results of this study permitted to propose some promising markers at the transcriptional and phenotypical level, responding to environmental concentrations of Cd. The present work also highlights the usefulness of the modified version of the medaka embryo-larval assay with sediment-contact exposure (MELAc) to investigate the toxicity and the modes of action of sediment-bound pollutants.

Toxic effects of magnesium oxide nanoparticles on early developmental and larval stages of zebrafish (Danio rerio).

Magnesium oxide nanoparticles (MgONPs) are used in medicine, manufacturing and food industries. Because of their extensive application in our daily lives, environmental exposure to these nanoparticles is inevitable. The present study examined the effects of MgONPs on zebrafish (Danio rerio) early developmental stages. The results showed that, at different concentrations, MgONPs induced cellular apoptosis and intracellular reactive oxygen species. The hatching rate and survival of embryos decreased in a dose dependent manner. The 96-h LC50 value of MgONPs on zebrafish survival was 428 mg/l and the 48-h EC50 value of MgONPs on zebrafish embryo hatching rate was 175 mg/l. Moreover different types of malformation were observed in exposed embryos. The results demonstrate the toxic effects of MgONPs on zebrafish embryos and emphasize the need for further studies.

Dynamics of PPARs, fatty acid metabolism genes and lipid classes in eggs and early larvae of a teleost.

Dietary long chain polyunsaturated fatty acids (FA) have been recognized of crucial importance in early development of vertebrates, contributing to the impressive morphological and physiological changes both as building blocks and to energy production. The importance of lipids along development depends on ontogenetic, phylogenetic and environmental parameters. The expression patterns of FA metabolism genes have not been characterized in developing fish embryos nor compared to lipid class profiles. Full lipid metabolism only occurred after hatching, as revealed by alterations in lipid profiles and FA gene expression. Nonetheless, transcriptional changes of some FA genes were already present in embryos at notochord formation. Many genes displayed an expression profile opposed to the decrease of lipids along the development, while others responded solely to starvation. Transcription of most genes involved in FA metabolism had a strong correlation to PPARs' mRNA levels (α1, α2, ß, γ). The comparison of mRNA expression of the genes with the lipid profiles produced new insights into the FA metabolism and regulation during the development of turbot larvae, providing the basis for future studies including comparative approaches with other vertebrate species.