Evidence cluster — Aquarium fish (teleost fish) toxicology (peer-reviewed, Europe PMC)

Evidence: Aquarium fish (teleost fish) toxicology

Source: Europe PMC (Europe PubMed Central) REST search — first-hand peer-reviewed abstract records, pulled 2026-08-01. Queries covered toxicology, poisoning, intoxication, heavy metals, mycotoxins and (for relevant taxa) envenomation for teleost fish. The cluster returns 12 representative studies with abstracts below. Abstract text is verbatim from source; each study is traceable by PMID.

Studies

• PMID 41719136 (2026, STAR protocols) — Protocol for blastomere injection to generate bilateral hemimosaic Xenopus tadpoles.. Abstract (opening): Here, we present a protocol to generate bilateral hemimosaic Xenopus tadpoles that allows systematic, independent manipulation of pre- and postsynaptic neurons in the tadpole retinotectal projection. We describe the steps to perform in vitro fertilization, followed by blastomere injections for two different manipulations. Specifically, we detail procedures for exogenous gene expression (GCaMP6s) by mRNA microinjection and endogenous gene knockdown (GluN1) with antisense morpholino microinjection. For complete details on the use and execution of this protocol, please refer to Kesner et al.¹ and Li et al.².

Source: https://pubmed.ncbi.nlm.nih.gov/41719136/

• PMID 41870694 (2026, Environmental monitoring and assessment) — Time and contamination level dependence of metal bioaccumulation and multibiomarker responses in fish: implications for biomonitoring.. Abstract (opening): This study evaluated how different levels of sediment metal contamination (ranging from below to above toxicity thresholds) and exposure durations (3-14 days) influence metal bioaccumulation and biomarker responses in fish under estuarine conditions. Using an integrated biomarker approach, the relationships among environmental contamination, metal accumulation, and fish health were examined to improve biomonitoring strategies. At the highest contamination level, 100% mortality was observed. Under low contamination, fish eliminated excess Cu, Zn, and Hg, whereas moderate contamination resulted in progressive accumulation of Cu and Zn; Pb accumulated under both exposure levels. Early biomarker responses included decreased GSH, inhibited GPx, increased lipid peroxidation, histopathological liver lesions, and neurotoxicity, followed by partial recovery. DNA damage increased over time and across contamination levels, likely due to impaired antioxidant defenses and/or direct metal-DNA interactions. Histopathological alterations were more strongly associated with sediment contamination than with tissue concentrations, indicating that body burdens may not fully represent exposure. GSH depletion and DNA damage were the most consistent biomarkers, whereas LPO and histopathology were sensitive primarily at early exposure stages. These findings reinforce the importance of considering both exposure duration and contamination level when interpreting biomarker responses and highlight the limitations of short-term or single-biomarker assessments. Biological effects detected at low to moderate contamination support the need for more precautionary sediment-quality thresholds. Overall, integrating biochemical, physiological, and histological biomarkers provides early detection of sublethal effects and a comprehensive assessment of ecosystem health. Consequently, a multibiomarker framework represents a powerful tool to strengthen the monitoring, evaluation, and management of aquatic environmental quality.

Source: https://pubmed.ncbi.nlm.nih.gov/41870694/

• PMID 41060374 (2026, Conservation biology : the journal of the Society for Conservation Biology) — Extent of threats to marine fish from the online aquarium trade in the United States.. Abstract (opening): The global marine aquarium hobby is a multibillion-dollar industry, largely driven by demand from the United States. Much of this trade occurs online. We web scraped 4 major US-based e-commerce platforms selling marine aquarium fish to determine the retail price and source (wild capture, aquaculture, or both) of 13 families of ray-finned marine fish (Actinopterygii). We supplemented this with ecological and economic trait data from FishBase and the International Union for Conservation of Nature (IUCN). Across all platforms and 13 popular fish taxonomic families, we found 734 unique species for sale, 89.2% (655 species) of which were sourced exclusively from the wild. A total of 45 species were of conservation concern (20 threatened species and 25 additional species with decreasing population trends), 38 of which were sourced solely from the wild. Retail price was significantly correlated with source, body length, minimum occupied depth, and schooling behavior. A further 100 species for sale were not listed as being in the aquarium trade in FishBase or by the IUCN, indicating incomplete information on this fishery in 2 important databases. For 58 species (encompassing 71 variants) with both wild-caught and captive-bred individuals for sale, aquaculture fish were a mean 28.1% (95% confidence interval 15.3) cheaper than their wild-caught counterparts.

Source: https://pubmed.ncbi.nlm.nih.gov/41060374/

• PMID 41857250 (2026, Parasitology research) — First record of Camallanus cotti (Fujita, 1927) in traded guppies (Poecilia reticulata) from India.. Abstract (opening): The guppy Poecilia reticulata is a widely traded ornamental fish species, valued for its popularity in aquariums globally. Parasitic infections pose a significant threat to both ornamental culture and native fish populations. This study records the first occurrence of the intestinal nematode Camallanus cotti (Fujita, 1927) in guppies from India, confirmed through both morphological and molecular analysis. Sixteen guppies were collected from the Kolathur ornamental fish market, Chennai, Tamil Nadu. Examination revealed that 11 fish (68.75%) were infected with red thread-like nematodes protruding from the anus. A total of 41 worms were recovered, with a mean intensity of 3.73 and a mean abundance of 2.56 worms per fish. Light microscopy confirmed diagnostic features of C. cotti, including the robust cephalic capsule and scanning electron microscopy illustrates the attachment of the parasite to intestinal wall. Molecular characterization using 18 S rRNA gene sequencing (GenBank Accession PX446961.1) showed 99.84% similarity with reference sequences, validating the morphological identification. Infected guppies exhibited visible clinical signs, including abdominal distension and threadlike worms protruding from the anus. The findings highlight the risk posed by C. cotti to ornamental fish health and emphasize the importance of quarantine, monitoring, and surveillance to prevent its spread through the aquarium trade.

Source: https://pubmed.ncbi.nlm.nih.gov/41857250/

• PMID 40810320 (2026, Journal of fish diseases) — Effects of Increased Water Salinity and Temperature on the Development of Rainbow Trout Fry Syndrome (RTFS) Caused by Flavobacterium psychrophilum.. Abstract (opening): Flavobacterium psychrophilum, the etiological agent of Rainbow Trout Fry Syndrome (RTFS) and Bacterial Coldwater Disease (BCWD), causes varying degrees of disease and mortality in salmonid aquaculture worldwide. Because its treatment relies on the use of antimicrobials, alternative interventions are of environmental and economic interest. As for other bacterial diseases, environmental factors like water parameters play a crucial role in the development of RTFS. In this study, we investigated the effect of either increased water salinity [1% (10 g L^-1)] or water temperature (18°C ± 1°C) on the development of RTFS following challenge with F. psychrophilum in rainbow trout fry under experimental conditions (either bath challenge or co-habitation challenge). When implemented after bath challenge, the salinity treatment delayed the appearance of clinical disease, while the temperature treatment reduced the incubation time to appearance of clinical disease. Given the positive effect of increased salinity, we further assessed the effect of the salinity treatment on disease transmission when the fish were exposed to co-habitation challenge. While intraperitoneally injected seeder fish died within 2 weeks independent of salinity, cohabitant fish kept in water with 1% salinity had a significant increase in survival (42.6%) compared to the positive controls (17.9%). Infected dead and moribund fish were confirmed positive for F. psychrophilum. Increasing water salinity thus delayed and partly prevented RTFS. In applied terms, such a delay may give time to achieve antimicrobial susceptibility test (AST) results and initiate treatment before reaching heavy mortalities in a fish batch. Further studies should evaluate the robustness of the preventive effect of this approach, its effect on the microbial communities (fish and farm environment) and whether it could be combined with other measures (e.g., phage therapy). The effect of the warm water was surprising, as F. psychrophilum infections are reported at colder temperatures.

Source: https://pubmed.ncbi.nlm.nih.gov/40810320/

• PMID 42456866 (2026, Fish & shellfish immunology) — Establishment of a novel brain cell line from grass carp (Ctenopharyngodon idella) with high transfection efficiency and CRISPR/Cas9-mediated genome editing capacity.. Abstract (opening): Fish cell lines serve as valuable tools in aquaculture research, particularly in immunology, pathology, and toxicology. In this study, we successfully established a novel cell line derived from brain tissue of grass carp, designated CIB. This cell line has been subcultured over 100 times and exhibits a fibroblast-like morphology. Chromosomal analysis revealed that the diploid chromosome number of CIB cells is 2n = 48, while sequencing of the 18S rRNA gene confirmed the cell line's origin. Notably, CIB cells demonstrated a transfection efficiency of 62.4% with pEGFP-N3, highlighting their potential for studies involving exogenous gene expression. Furthermore, CIB cells were susceptible to grass carp reovirus genotype I (GCRV-I), as evidenced by cytopathic effects (CPE), increased synthesis of viral proteins, and accumulation of viral particles within the cells. Both viral infection and poly(I:C) stimulation significantly increased the expression of intracellular interferon-related signaling molecules. Additionally, electroporation of a gRNA-Cas9 ribonucleoprotein (RNP) complex into CIB cells achieved the first successful large-fragment gene knockout in cultured grass carp cells and generated a homozygous clonal line, thereby enhancing the antiviral response. In summary, this novel cell line represents a significant advancement for studying gene functions, host-virus interactions, and genetic engineering in teleost fish.

Source: https://pubmed.ncbi.nlm.nih.gov/42456866/

• PMID 41703611 (2026, Environmental toxicology and chemistry) — Temperature-dependent effects of the Brazilian oil spill to early life stages of Danio rerio.. Abstract (opening): Exposure of fish early life stages to polycyclic aromatic hydrocarbons (PAHs) causes negative impacts on the development of teleost fish, which can be exacerbated by rising global temperatures. This study investigated the combined effects of exposure to oil water accommodated fractions from the spill that affected the Brazilian northeast and rising temperatures on early development of the zebrafish Danio rerio. Exposure to PAHs caused developmental delay and increased frequency of malformations at 16.47 and 32.95 μg-∑PAHt L-1 at 28, 30, and 32 °C. Incomplete mandible development was not verified after PAH exposure at 28 °C, but increased with increasing temperatures. Increased frequency of malformations included thrombosis, deformed heart, pericardial and yolk-sac edemas, and spinal kyphosis. Heart rates increased with increasing temperature in control larvae and with increasing PAH concentrations at 28 and 30 °C, but not at 32 °C. Total length, eye, and swim bladder area of larvae at 168 hr post-fertilization decreased with increasing PAH concentrations and increasing temperatures, indicating an additive interaction. Acetylcholinesterase activity in control larvae increased with increasing temperatures and decreased with increasing PAH concentrations. Combined exposure to PAHs and temperature elevation intensified developmental delays and teratogenic outcomes, posing additional threats to the viability of D. rerio early life stages. Results indicate that temperature effects should be considered in oil spill risk assessments under climate change scenarios.

Source: https://pubmed.ncbi.nlm.nih.gov/41703611/

• PMID 41640276 (2026, FEBS letters) — A fresh perspective-advancing fish immunotoxicology in a complex world.. Abstract (opening): Understanding how environmental changes affect the health of organisms and ecosystems is complex, but recent interdisciplinary advances and the recognition of immune function as a dynamic mediator offer exciting progress. Environmental immunotoxicology in teleost fishes is evolving beyond cataloguing stressors towards a mechanistic, integrative framework that leverages omics, in vivo tracking and cross-disciplinary modelling. However, knowledge gaps in immune mechanisms, toxicokinetics and multi-stressor interactions remain. The present work highlights these gaps, advocating for immune function as both a mechanistic lens and an integrative health indicator. Such a framework can improve predictive risk assessments, management strategies and our understanding of contaminant effects on resilience, disease susceptibility and population viability. While challenges remain, the field is poised for significant growth through collaborative innovation and advancing technology.

Source: https://pubmed.ncbi.nlm.nih.gov/41640276/

• PMID 40902923 (2026, Comparative biochemistry and physiology. Toxicology & pharmacology : CBP) — Effects of short-term exposure to environmentally relevant pesticides mixture on morphological alterations, oxidative-nitrative stress biomarkers, cellular apoptosis, and antioxidant expression in kidneys of goldfish.. Abstract (opening): Chemical stressors are pervasive, affecting both terrestrial and aquatic environments. The continual influx of these toxins is damaging ecosystems and the organisms that inhabit them. The abundance of environmental toxins makes aquatic habitats inhospitable for aquatic life. These chemical stressors consistently disrupt the life processes of aquatic organisms, particularly their physiological functions. This study examined on the effects of environmentally relevant pesticides mixture (low-dose and high-dose: S-metolachlor: 2.4 go/L, 12 μg/L; linuron: 2.0 μg/L, 10 μg/L; isoproturon: 1.2 μg/L, 6.0 μg/L; tebucanozole: 1.2 μg/L, 6.0 μg/L; aclonifen: 0.8 μg/L, 4.0 μg/L; atrazine: 0.4 μg/L, 2.0 μg/L; pendimethalin: 0.4 μg/L, 2.0 μg/L, and azinphos-methyl: 0.8 μg/L, 4.0 μg/L) on tissue morphology, cellular apoptosis, and nitrotyrosine protein (NTP), dinitrophenyl protein (DNP), renin, superoxide dismutase (SOD), and catalase (CAT) expression in the kidneys of goldfish (Carassius auratus) exposed for one week under controlled laboratory conditions. Histopathological analysis revealed severe tissue damage in the kidneys, while silver staining identified melano-macrophage centers, and immunohistochemistry and real-time PCR shed light on the expression of molecular biomarkers in these tissues. Exposure to pesticide mixtures caused fish to exhibit glomerular shrinkage, enlargement of Bowman's space, and degradation of glomerular cells. Moreover, the expression of renin, DNP, NTP, SOD, and apoptotic nuclei increased in kidney tissues, while CAT expression decreased. Overall, our findings indicate that exposure of goldfish to an environmentally relevant pesticide mixture leads to increased cellular damage and altered osmoregulatory and antioxidant enzyme expressions, which may impair physiological functions, including growth, reproduction, and development in teleost fish.

Source: https://pubmed.ncbi.nlm.nih.gov/40902923/

• PMID 41727407 (2026, Toxicology reports) — Direct adverse effects of fipronil sulfone, diisopentyl phthalate and disperse red 60 on zebrafish hepatocytes.. Abstract (opening): The major concerns about emerging pollutants fipronil sulfone, disperse red 60 (DR60), and diisopentyl phthalate (DiPP) include their environmental persistence, difficulty in its removal from water sources, and bioaccumulation in aquatic organisms. They could eventually enter the food chain and raise potential risks to human health. This research investigated whether the above-mentioned emerging contaminants directly affect cellular processes supporting metabolic homeostasis and female reproductive success in teleost fish, using zebrafish hepatocytes (ZFL liver cell line) <i>in vitro</i>. RT-qPCR analysis demonstrated that exposure to all three chemicals led to significant alterations in several key reproductive and metabolic genes. For example, DiPP and DR60 caused an increase in cytochrome P450 family 1 alpha (<i>cyp1α</i>), kisspeptin 1 (<i>kiss1</i>), and vitellogenin 1 (<i>vtg1</i>), and a decrease in cytochrome P450 family 3 subfamily A polypeptide 65 (<i>cyp3a65</i>) and peroxisome proliferator activated receptor alpha (<i>pparα</i>). A significant increase in cellular vitellogenin and triglyceride levels was also caused by all three compounds. Additionally, triglyceride levels in ZFL cells were increased by all three compounds, consistent with a gene expression profile, suggestive of a metabolic shift favoring lipid storage over catabolism. These findings show direct cellular adverse effects for fipronil sulfone, DiPP, and DR60, even at low yet environmentally relevant concentrations. The outcomes suggest their potential to disrupt metabolic and reproductive processes in teleosts <i>in vivo</i>.

Source: https://pubmed.ncbi.nlm.nih.gov/41727407/

• PMID 41823821 (2026, Biology) — Behavioral Alterations in Male Zebrafish After Administration of Androgen Receptor Blockers and an Activator.. Abstract (opening): Androgen receptor (AR) signaling is crucial for mediating male-typical behaviors across vertebrates. Enzalutamide (ENZ) and apalutamide (APA) are two second-generation androgen receptor inhibitors (SGARIs) that have been primarily used in the treatment of prostate cancer. However, these drugs still possess side effects, and there remains limited information regarding their behavioral and neurophysiological impacts following chronic exposure in non-mammalian animal models, particularly in fish. Thus, this study aimed to evaluate the behavioral alterations in adult male zebrafish (<i>Danio rerio</i>) following exposure to specific AR blockers (ENZ and APA) and an activator, dihydrotestosterone (DHT), to provide a comprehensive comparison between each tested drug. Adult male zebrafish were exposed via aqueous immersion to each compound at a 1 ppm concentration for ~2 weeks and were subjected to a battery of behavioral tests. From the results, both AR blockers were found to slightly compromise fish locomotion, with contrary results observed in DHT-treated fish, which displayed an increased locomotor activity together with slight alterations in fish exploratory behaviors. Furthermore, ENZ also caused a tightened shoal formation in zebrafish, while exposure to APA was observed to slightly diminish the fear response of fish. On the other hand, the DHT-treated group displayed a higher level of aggression compared to the vehicle control group. In conclusion, functional modulation of androgen receptor signaling leads to significant alterations in male zebrafish behavior, particularly affecting fear responses, aggression, and anxiety-related behaviors. We believe that these findings could contribute to a deeper understanding of the relationship between androgens and behaviors in vertebrates, especially zebrafish.

Source: https://pubmed.ncbi.nlm.nih.gov/41823821/

• PMID 40898728 (2026, Journal of applied toxicology : JAT) — A Multimodal Approach to Identify Metallothionein Metal Inducers in Nile Tilapia: Insights From Molecular Docking and Hepatocyte Exposure.. Abstract (opening): Many human activities contribute to the pollution of aquatic ecosystems, primarily through agricultural, industrial, mining, and domestic discharges into water bodies. Fish, being highly sensitive to environmental changes, serve as valuable models for monitoring the health of these ecosystems. Metallothionein (Mt), a biomarker for metal contamination, shows variable expression depending on the metal involved. Transcription of the mt gene is regulated by intracellular metal concentrations and mediated by interactions between metal-responsive transcription factors (Mtf) and metal response elements (MRE) in the mt promoter. Zinc plays a key role by binding to Mtf, activating it, and enabling interaction with MRE sequences to initiate transcription. In this context, this study aimed to identify the most potent inducers of mt expression in Oreochromis niloticus. Initially, zinc-binding proteins from O. niloticus were modeled to assess differential binding scores of various metals using molecular docking, which suggested the potency ranking Cd²⁺ > Cu²⁺ > Mn²⁺ > Hg²⁺ > Pb²⁺. These predictions were validated using primary hepatocytes exposed to concentrations 10 times higher than the maximum allowed for effluent discharge under Brazilian law. The expression of both mt mRNA and Mt protein was evaluated in hepatocytes. Both in silico and in vitro results identified cadmium as the most potent inducer of Mt. Other metals did not induce mt expression under the tested conditions. These findings underscore the importance of understanding how Mt expression varies by metal and tissue, as differences in responsiveness can influence the interpretation of Mt levels in teleost fish used for water quality monitoring and environmental toxicology.

Source: https://pubmed.ncbi.nlm.nih.gov/40898728/

Source text: pdf-raw/evidence/europepmc_fish_toxicology_2026-08-01.txt (Europe PMC first-hand abstracts, pulled 2026-08-01).