In vertebrates, evolutionarily conserved signaling intermediate in the Toll pathway (ECSIT) interacts with the TNF-receptor associated factor 6 (TRAF6) to regulate the processing of MEKK1, activate NF-κB, and also control BMP target genes. However, the role of ECSIT in invertebrates remains largely unexplored. We performed comparative investigations of the expression, gene structure, and phylogeny of ECSIT, Tolllike receptor (TLR), and Smad4 in the cephalochordate Branchiostoma belcheri. Phylogenetic analysis indicated that, in amphioxus, ECSIT, TLR, and Smad4 form independent clusters at the base of Chordate clusters. Interestingly, overall gene structures were comparable to those in vertebrate orthologs. Transcripts of AmphiECSIT were detectable at the mid-neural stage, and continued to be expressed in the epithelium of the pharyngeal region at later stages. In adult animals, strong expression was observed in the nerve cord, endostyle, epithelial cells of the gut and wheel organ, genital membrane of the testis, and coelom and lymphoid cavities, what is highly similar to AmphiTLR and AmphiSmad4 expression patterns during development and in adult organisms. Our data suggests that ECSIT is evolutionarily conserved. Its amphioxus ortholog functions during embryonic development and as part of the innate immune system and may be involved in TLR/BMP signaling.

•Chronic low-dose BPA disturbed color discrimination.•BPA alleviated anxiety behavior.•BPA altered the ability to adapt to the environment.The extensive usage of xenobiotic endocrine disrupting chemicals (XEDCs), such as Bisphenol A (BPA), has created obvious threat to aquatic ecosystems worldwide. Although a comprehensive understanding of the adverse effect of BPA on behaviors and physiology have been proven, the potential impact of low-dose BPA on altering the basic ability of aquatic organism in adapting to the surrounded complex environment still remains elusive. In this research, we report that treatment of adult male zebrafish with chronic (7 weeks) low-dose (0.22 nM–2.2 nM) BPA, altered the ability in adapting the complex environment by disturbing the natural color preference patterns. In addition, chronic 50 ng/L (0.22 nM) BPA exposure alleviated the anxiety behavior of male zebrafish confronted with the novel environment by enhancing the preference towards light in the light/dark preference test. This phenotype was associated with less expression of serotonin (5-TH) in the hypothalamus and the down-regulation of tyrosine hydroxylase (TH) in brain tissues. As such, our results show that low-dose BPA remnant in surface waters altered zebrafish behavior that are known to have ecological and evolutionary consequences.HighlightsHere we reported that the impact of chronic low-dose BPA exposure on the basic capability of zebrafish to adapt to the environmental complexity. Specifically, BPA at low concentration, under the environmental safety level and 3000-fold lower than the accepted human daily exposure, interfered with the ability to discriminate color and alleviate anxiety induced by the novel environment, which finally altered the capability of male zebrafish to adapt to the environmental complexity. These findings revealed the ecological effect of low-dose BPA and regular BPA concentration standard are not necessarily safe. The result also provided the consideration of retuning the hazard concentration level of BPA.Download high-res image (413KB)Download full-size image

Glucocorticoid receptors (GRs) exert actions on the hippocampus that are important for memory formation. There are correlations between vascular dysfunctions and GR-related gene expression. Both vascular dysfunction and GR gene expression decline occur during the ageing process. Therefore, hypotensors, which have effects on improving vascular dysfunction, may be able to ameliorate GR gene expression decline in ageing mice and improve ageing-mediated memory deficits. In this study, we hypothesized that hypotensors could alleviate the decline of GR gene expression and ameliorate age-induced learning and memory deficits in a d-gal-induced ageing mice model. In line with our hypothesis, we found that chronic d-gal treatment decreased GR and DCX expression in the hippocampus, leading to learning and memory deficits. Amlodipine (AM) and puerarin (PU) treatment improved GR gene expression decline in the hippocampus and ameliorated the learning and memory deficits of d-gal-treated mice. These changes correlated with enhanced DCX expression and brain-derived neurotrophic factor (BDNF) expression in the hippocampus. Furthermore, PU treatment conveyed better effects than AM treatment, but combination therapy did not enhance the effects on improving GR expression. However, we did not find evidence of these changes in non-d-gal-treated mice that lacked GR gene expression decline. These results suggest that AM and PU could improve d-gal-induced behavioural deficits in correlation with GR gene expression.

•Low-dose BPA induced physiological abnormality of male adult zebrafish.•Low-dose BPA disturbed the courtship behavior of male.•Female chose male through socially mutual interaction, based on visual discrimination.The ubiquity of environmental pollution by endocrine disrupting chemicals (EDCs) such as bisphenol A (BPA) is progressively considered as a major threat to aquatic ecosystems worldwide. Numerous toxicological studies have proved that BPA are hazardous to aquatic environment, along with alterations in the development and physiology of aquatic vertebrates. However, generally, there is a paucity in knowledge of behavioural and physiological effects of BPA with low concentration, for example, 0.22 nM (50 ng/L) and 2.2 nM (500 ng/L). Here we show that treatment of adult male zebrafish (Danio rerio) with 7 weeks low-dose (0.22 nM–2.2 nM) BPA, resulted in alteration in histological structure of testis tissue and abnormality in expression levels of genes involved in testicular steroidogenesis. Furthermore, low-dose BPA treatment decreased the male locomotion during courtship; and was associated with less courtship behaviours to female but more aggressive behaviours to mating competitor. Interestingly, during the courtship test, we observed that female preferred control male to male under low-dose BPA exposure. Subsequently, we found that the ability of female to chose optimal mating male through socially mutual interaction and dynamics of male zebrafish, which was based on visual discrimination. In sum, our results shed light on the potential behavioural and physiological effect of low-dose BPA exposure on courtship behaviours of zebrafish, which could exert profound consequences on natural zebrafish populations.Download high-res image (225KB)Download full-size image

•CuO-NPs disturb the dorsoventral patterning by increasing wnt8 and vent expression.•CuO-NPs affect convergent extension by decreasing wnt5 and wnt11.•CuO-NPs prevent the looping of heart tube.•CuO-NPs affect the neural development in morphology and genes expression.Currently, nanoparticles are widely used in biomedicine and industry. CuO nanoparticles (CuO-NPs) are versatile materials in our daily life and their toxicity has drawn extensive attention. In this study, we concentrate on the effect of CuO-NPs on early zebrafish development. The results reveal that CuO-NPs can induce abnormal phenotypes of a smaller head and eyes and delayed epiboly. The gene expression pattern shows that CuO-NPs spatially narrow the expression of dorsal genes chordin and goosecoid and alter the expression of dlx3, ntl and hgg which are related to the cell migration of gastrulation. The decreased expression of pax2 and pax6 involved in neural differentiation was accordant with the decreased sizes of neural structures. Cmlc2 expression suggests that CuO-NPs prevented looping of the heart tube during cardiogenesis. Furthermore, quantitative RT-PCR results suggest that the CuO-NPs could increase the canonical Wnt signaling pathway to narrow the expression of chordin and goosecoid in dorsoventral patterning as well as decrease the transcription of Wnt5 and Wnt11 to result in slower, less directed movements and an abnormal cell shape. These findings indicated the CuO-NPs exert developmental toxicity. The present study evaluates the ecological and developmental toxicity, providing warnings about the application of CuO-NPs.

The name of the first author should read Y. S. Lin.

•High concentrations of glyphosate can induce zebrafish development delay and embryonic death.•Biomechanics analysis indicates the surface tension of chorion is decreased after glyphosate exposure.•Embryonic exposure to glyphosate damages embryos CaP axons and induces larval locomotor activities increased.All of these days, residues of herbicides such as glyphosate are widely distributed in the environment. The ubiquitous use of glyphosate has drawn extensive attention to its toxicity as an organic pollutant. In this study, we employed larval zebrafish as an animal model to evaluate the effect of different concentrations of glyphosate on early development via morphological, biomechanics, behavioral and physiological analyses. Morphological results showed that an obvious delay occurred in the epiboly process and body length, eye and head area were reduced at concentrations higher than 10 mg/L. The expression of ntl (no tail) shortened and krox20 (also known as Egr2b, early growth response 2b) changed as the glyphosate concentration increased, but there was no change in the expression of shh (sonic hedgehog). In addition, biomechanical analysis of the elasticity of chorion indicated that treated embryos' surface tension was declined. Furthermore, a 48-h locomotion test revealed that embryonic exposure to glyphosate significantly elevated locomotor activities, which is probably attributed to motoneuronal damage. The decreased surface tension of chorion and the increased locomotive activities may contribute to the hatching rates after glyphosate treatment. Our study enriches the researches of evaluating glyphosate toxicity and probablely plays a warning role in herbicides used in farming.Download high-res image (257KB)Download full-size image

The extensive employment of engineered nanoparticles (NPs) makes it inevitable that the environment would be exposed to nano-materials. As a result, their biological effects on the ecosystem and living organisms are gaining attention. Here, we report that both nano-silica (SiO2-NPs) and reserpine can elicit depression-like behavior in adult zebrafish in a novel tank test. Nano-silica or reserpine induce the depressive phenotype by decreasing locomotion, inhibiting exploratory behavior, aggravating the depressive phenotype and disturbing swimming patterns. Immunohistochemistry reveals that the dampened locomotion induced by nano-silica and reserpine is associated with the reduced expression of tyrosine hydroxylase. Inhibited exploratory behavior, aggravated depressive phenotypes, and disturbed spatiotemporal swimming path patterns are related to the increased expression of serotonin. These findings imply that the similar behavioral and depression-inducing effect of nano-silica and reserpine may share a common physiological mechanism. In summary, our results suggest that exposure to silica nanoparticles in the nervous system is a possible depression-inducing factor.

Nanoparticles are widely used in nanomedicine, raising concerns about their toxicity. In this study, the toxicity of bismuth–asparagine coordination polymer spheres (BACP-2) was assessed in zebrafish embryos. Injection of 1–4 cell stage embryos with BACP-2 resulted in smaller head size (particularly smaller eye size), shorter body length, and pericardial edemas. The severity and occurrence of the resulting phenotype were concentration-dependent. The expression of genes such as krox20, orthodenticle homeobox 2 (otx2), and cardiac myosin light chain-2 (cmlc2) indicates that the effects of BACP-2 on the head and heart were related to changes in gene expression patterns. A delay in epiboly was observed, and the expression levels of the no tail (ntl) gene indicated that the delay in epiboly resulted both from the effect of BACP-2 on cell migration during epiboly and from slow growth. These findings indicate that BACP-2 exhibits concentration-dependent developmental toxicity, providing insight into the nanotoxicity of bismuth derivatives, which must be rigorously evaluated with respect to toxicity before their application in nanomedicine.

The unique behaviors of engineered nanomaterials (eNMs) bring many exciting applications, and also raise safety concerns. Zebrafish have been widely used as a model organism for toxicity tests of eNMs. Commonly, the equivalent toxic dose of the drug is estimated by the level of malformation in zebrafish at 5 or 6 days post-fertilization (dpf). However, this method is only suitable for the evaluation of general toxicity. To distinguish the specific aspects of the drug, a much more sensitive approach is needed. Here, we first evaluated the toxicity of NPs that are largely composed of poly(ethylene glycol dimethacrylate-co-methacrylic acid) (P(EGDMA-co-MAA)). Surprisingly, statistical analysis of the data did not show eNMs toxicity in zebrafish embryos with chorions compared with the control. To further determine the effects of P(EGDMA-co-MAA) on the embryonic development of zebrafish, we stripped the chorions of 1-dpf embryos and exposed them to P(EGDMA-co-MAA). As early as 2 dpf, the embryonic mortality and teratogenicity were significantly elevated, suggesting that the chorion acts as a protective barrier against P(EGDMA-co-MAA). In addition, the data imply that P(EGDMA-co-MAA) shows low toxicity in zebrafish larvae (3–5 dpf) because the fish are mature enough to resist damage from eNM exposure. These data suggest that evaluation of eNMs toxicity at different developmental stages of dechorionated in zebrafish is a more sensitive method than more traditional analyses. Furthermore, the mechanism of interactions between eNMs and dechorionated zebrafish 2 dpf should be clarified in future studies to create less toxic eNMs for use as drug-delivery vectors.