Swimming activity in zebrafish larvae exposed to veterinary antiparasitic pharmaceuticals

Developmental Toxicity of PEDOT:PSS in Zebrafish: Effects on Morphology, Cardiac Function, and Intestinal Health

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a conductive polymer commonly used in various technological applications. However, its impact on aquatic ecosystems remains largely unexplored. In this study, we investigated the toxicity effects of PEDOT:PSS on zebrafish. We first determined the lethal concentration (LC50) of PEDOT:PSS in zebrafish and then exposed AB-type zebrafish embryos to different concentrations of PEDOT:PSS for 120 h. Our investigation elucidated the toxicity effects of zebrafish development, including morphological assessments, heart rate measurements, behavioral analysis, transcriptome profiling, and histopathological analysis. We discovered that PEDOT:PSS exhibited detrimental effects on the early developmental stages of zebrafish, exacerbating the oxidative stress level, suppressing zebrafish activity, impairing cardiac development, and causing intestinal cell damage. This study adds a new dimension to the developmental toxicity of PEDOT:PSS in zebrafish. Our findings contribute to our understanding of the ecological repercussions of PEDOT:PSS and highlight the importance of responsible development and application of novel materials in our rapidly evolving technological landscape.

Integrating morphological, biochemical, behavioural, and molecular approaches to investigate developmental toxicity triggered by tebuthiuron in zebrafish (Danio rerio)

Tebuthiuron (TBU), a phenylurea herbicide, is widely applied in agricultural and non-agricultural soils. Because TBU resists degradation, it can contaminate water and reach the biota once it is released into the environment. However, the potential toxic effects of TBU on aquatic developing organisms have been poorly studied. By taking advantage of the early-life stages of zebrafish (Danio rerio), we have combined morphological, biochemical, behavioural, and molecular approaches to investigate the developmental toxicity triggered by environmentally relevant concentrations (from 0.1 to 1000 μg/L) of TBU. Exposure to TBU did not elicit morphological abnormalities but it significantly delayed hatching. In addition, TBU altered the frequency of tail coils in one-day post-fertilization (dpf) old embryos. Moreover, TBU exposure during four days significantly inhibited the whole body AChE activity of larvae. At the molecular level, TBU did not significantly affect the mRNA levels of four genes (elavl3, gfap, gap43, and shha) that play key roles during the neurodevelopment of zebrafish. By assessing the motor responses to repeated light-dark stimuli, 6 dpf larvae exposed to TBU displayed hyperactivity, showing greater travelling distance during the dark periods. Our categorization of swimming speed revealed an interesting finding - after the light was turned off, the exposed larvae abandoned the freezing mode (<2 mm/s) and travelled mainly at cruising speed (2-20 mm/s), showing that the larval hyperactivity did not translate into higher swimming velocity. Overall, our results offer new insights into the TBU toxicity to developing organisms, namely effects in AChE activity and hyperactivity, providing support data for future studies considering environmental risk assessment of this herbicide.

A review on the ecotoxicity of macrocyclic lactones and benzimidazoles on aquatic organisms

Despite its wide production and several applications, veterinary antiparasitics from macrocyclic lactones and benzimidazole classes have not received much scientific attention concerning their environmental risks. Thus, we aimed to provide insights into the state of the environmental research on macrocyclic lactone and benzimidazole parasiticides, emphasizing their toxicity to non-target aquatic organisms. We searched for relevant information on these pharmaceutical classes on PubMed and Web of Science. Our search yielded a total of 45 research articles. Most articles corresponded to toxicity testing (n = 29), followed by environmental fate (n = 14) and other issues (n = 2) of selected parasiticides. Macrocyclic lactones were the most studied chemical group (65% of studies). Studies were conducted mainly with invertebrate taxa (70%), with crustaceans being the most predominant group (n = 27; 51%). Daphnia magna was the most used species (n = 8; 15%). Besides, it also proved to be the most sensitive organism, yielding the lowest toxicity measure (EC₅₀ 0.25 μg/L for decreased mobility after 48 h-abamectin exposure) reported. Moreover, most studies were performed in laboratory settings, tracking a limited number of endpoints (acute mortality, immobility, and community disturbance). We posit that macrocyclic lactones and benzimidazoles warrant coordinated action to understand their environmental risks.

Migration and toxicity of toltrazuril and its main metabolites in the environment

Veterinary drugs heavily used in livestock are passed into the environment through different ways, resulting in risks to terrestrial environments and humans. The migration of toltrazuril (TOL), an important anticoccidial drug used intensively in livestock, and its main metabolites between the chicken manure compost, soil and vegetables was investigated, and then the impacts of TOL on the soil bacterial community and ARGs, soil enzyme activities and phytotoxicity were detected. In the process of aerobic composting for 80 days, except for toltrazuril sulfoxide (the degradation half-life was 59.74 d), TOL and ponazuril (PON) were not significantly degraded. However, TOL and its metabolites were significantly degraded in fertilized soil, and the degradation half-life was 28.17-346.50 d. Among the three drugs, only PON could migrate from soil to vegetables, and the residual concentrations of PON in lettuce and radish were 2.64-70.02 μg kg-1 and 0-2.80 μg kg-1, respectively. Moreover, TOL and its main metabolisms had no significant effect on the bacterial community structure and the abundance of antibiotic resistance genes during composting, but affected the microbial activity in the soil. The presence of TOL and its main metabolites reduced soil urease activity, increased catalase activity, and decreased alkaline phosphatase activity at the beginning and then increased slightly. They had negative effects on plant growth. Compared with the control group, the inhibition rates of TOL and its metabolites on lettuce and radish seed germination were 8.33% and 26.74% respectively, and the inhibition rates of root elongation length were 25.88% and 34.45% respectively. These results showed that TOL and its main metabolites were ineffectively removed by aerobic composting, and could be migrated from composting to soil and vegetables, which had adverse effects on soil enzyme activity and plant growth. Therefore, its environmental ecological risk and human health risk needs to be further evaluated.

Occurrence and Effects of Antimicrobials Drugs in Aquatic Ecosystems

Currently, thanks to the development of sensitive analytical techniques, the presence of different emerging pollutants in aquatic ecosystems has been evidenced; however, most of them have not been submitted to any regulation so far. Among emerging contaminants, antimicrobials have received particular attention in recent decades, mainly due to the concerning development of antibiotic resistance observed in bacteria, but little is known about the toxicological and ecological impact that antimicrobials can have on aquatic ecosystems. Their high consumption in human and veterinary medicine, food-producing animals and aquaculture, as well as persistence and poor absorption have caused antimicrobials to be discharged into receiving waters, with or without prior treatment, where they have been detected at ng-mg L−1 levels with the potential to cause effects on the various organisms living within aquatic systems. This review presents the current knowledge on the occurrence of antimicrobials in aquatic ecosystems, emphasizing their occurrence in different environmental matrixes and the effects on aquatic organisms (cyanobacteria, microalgae, invertebrates and vertebrates).

Effects of antidepressants with different modes of action on early life stages of fish and amphibians

Drugs are excreted from the human body as both original substances and as metabolites and enter aquatic environment through waste water. The aim of this study was to widen the current knowledge considering the effects of waterborne antidepressants with different modes of action-amitriptyline, venlafaxine, sertraline-on embryos of non-target aquatic biota-fish (represented by Danio rerio) and amphibians (represented by Xenopus tropicalis). The tested concentrations were 0.3; 3; 30; 300 and 3000 μg/L in case of amitriptyline and venlafaxine and 0.1; 1; 10; 100 and 1000 μg/L for sertraline. Test on zebrafish embryos was carried out until 144 h post fertilization, while test on Xenopus embryos was terminated after 48 h. Lethal and sublethal effects as well as swimming alterations were observed at higher tested concentrations that are not present in the environment. In contrast, mRNA expression of genes related to heart, eye, brain and bone development (nkx2.5, otx 2, bmp4 and pax 6) seems to be impacted also at environmentally relevant concentrations. In a wider context, this study reveals several indications on the ability of antidepressants to affect non target animals occupying environments which may be contaminated by such compounds.