Aug 2026· Aquatic Toxicology· Vol 299, pp.
107970
· 0 citations· 65 references
Medicine
TL;DR
While acute ammonia exposure induces inflammation in the Striped catfish skin, active ammonia excretion along with exosomes may alleviate accumulation, thereby maintaining skin tissue integrity.
Abstract
Ammonia can rapidly accumulate in a water body and pose a serious threat to fish health. Striped catfish is a key species in Southeast Asia. Climate change and intensive farming waste pose significant risks of ammonia stress to this species in both natural habitats and farming ponds. As a vital immune-related organ and a significant surface barrier, the fish skin plays a crucial role in defending against ammonia; however, little is known about skin response to acute ammonia exposure. In this study, Striped catfish were exposed to 40 mg L-1 concentration of total ammonia for 24 hr to evaluate skin responses. In general, we found inflammation in the skin. However, the skin tissue showed subtle to no signs of damage, with tissue ammonia concentration accumulating and then decreasing over the challenge duration. Subsequent transcriptomic analysis of skin gene functions suggests that overall ammonia regulation may occur along with specific cellular components. Transmission electron microscopy then revealed accumulated exosome-like vesicles near the epithelial surface of the skin's superficial layer during challenge. Using the established Striped catfish skin epithelial cell line along with an exosome inhibitor, we confirmed the presence of exosomal vesicles and their role in ammonia excretion. In conclusion, while acute ammonia exposure induces inflammation in the Striped catfish skin, active ammonia excretion along with exosomes may alleviate accumulation, thereby maintaining skin tissue integrity. This study explores the Striped catfish skin responses to acute ammonia exposure and highlights the ammonia regulation system that maintains skin integrity.
Pesticides play a crucial role in agriculture, public health management, and veterinary practice to control pests. However, the persistent use of pesticides poses a significant threat to aquatic ecosystems and non-target organisms, such as fish. The genotoxicity, oxidative stress, and erythrocytic toxicity were assessed in fish exposed to different sublethal concentrations (5, 10, and 15 µg/L) of thiram for 12 days. Blood and other tissues (gills and intestine) were obtained from each fish reared in each group at days 4, 8, and 12 of the experiment. Thin blood film/smear examination indicated significantly (P ≤ 0.05) increased morphological and nuclear changes in erythrocytes, such as the formation of micronuclei, notched nuclei, lobed nuclei, and tear-shaped erythrocytes in fish exposed to higher doses of thiram. The contents of antioxidant enzymes such as catalase (CAT), reduced glutathione (GSH), peroxidase (POD), and superoxide dismutase (SOD) were significantly (P ≤ 0.05) decreased and the oxidative stress biomarkers including reactive oxygen species (ROS) and thiobarbituric acid reactive substances (TBARS) were significantly (P ≤ 0.05) increased in gills and intestinal tissues of exposed fish. The results on genotoxicity determined using the comet assay technique revealed significantly (P ≤ 0.05) high levels of genomic instability in terms of DNA damage in isolated cells of the gills and intestine of fish reared in water containing higher concentrations of thiram. At the microscopic level, various sections of the gills of fish treated with higher doses of thiram unveiled moderate to severe histopathological ailments such as degeneration of cartilaginous core, degeneration and disruption of primary and secondary lamellae of gills, necrosis of lamellar epithelial cells, telangiectasia, and curling of secondary lamellae. The findings of this study indicated that extremely low doses of thiram lead to the induction of adverse effects in freshwater fish. Hence, there is a need to develop suitable control measures regarding the use of environmentally friendly chemicals and for the protection of aquatic environments.
Methyl parathion, a highly toxic organophosphorus insecticide, is widely employed in agriculture. Runoff from these fields frequently pollutes freshwater ecosystems, endangering non-target aquatic life. This study assessed the acute toxicity of methyl parathion on the freshwater catfish Heteropneustes fossilis (Bloch) in a controlled laboratory setting. Healthy fish were subjected to varying concentrations of methyl parathion in static bioassay systems over a 96-hour period. Mortality rates, behavioral changes, and toxic symptoms were documented at 24, 48, 72, and 96-hour intervals. The median lethal concentration (LC₅₀) was calculated using probit analysis. Fish exposed to the chemical displayed hyperactivity, erratic swimming, and excessive mucus production, loss of balance, breathing difficulties, and surfaced frequently before dying. Previous studies have reported the 96-hour LC₅₀ value for H. fossilis to be approximately 7.0 ppm, indicating the species' high sensitivity to organophosphate pesticides. These findings reveal that methyl parathion poses substantial ecological threats to freshwater fish populations and can negatively impact aquatic biodiversity. The study underscores the importance of stringent regulation of pesticide application near aquatic habitats.
Chandra Shekhar Ramanuj Raman· Research Journal of Science...· 0 citations
Uranium mining and tailings disposal may affect nearby aquatic environments through the release or mobilisation of sediment-associated contaminants. The present study examined liver histopathology in Clarias batrachus exposed under laboratory conditions to a soil suspension collected from the Jaduguda uranium waste-dumping area. Control fish were maintained in water collected from Ghatshila. Twelve healthy fish were acclimatised for seven days and divided into control and exposed groups, with six fish in each group. The exposed group was maintained for 30 days in 20 L of collected water mixed with 400 g of soil, corresponding to a sediment load of 20 g/L. After the exposure period, surviving fish from both groups were transferred to clean water for a further 30 days to assess tissue recovery. Liver tissues were processed following a routine histological protocol and stained with haematoxylin and eosin. Control fish showed compact hepatic cords, distinct hepatocytes, centrally placed nuclei and regular sinusoidal spaces. In contrast, exposed fish showed marked histopathological alterations, including cytoplasmic vacuolisation, hepatocellular degeneration, nuclear pyknosis and karyolysis, sinusoidal dilation, disruption of hepatic organisation and focal necrotic changes. Fish transferred to clean water after exposure showed partial improvement in hepatic organisation, with reduced degeneration and better cellular arrangement. However, residual vacuolisation, focal necrosis and mild tissue disorganisation persisted in the liver sections of recovery-group fish. These observations indicate that exposure to soil suspension collected from the Jaduguda uranium tailings area was associated with hepatic tissue injury in C. batrachus under the experimental conditions used. The findings also suggest that recovery may begin after removal from the exposure condition, although complete histological restoration was not evident within 30 days.
Ramita Kumari, Ashwini Tigga, Deepshikha Samdershi et al.· Asian Journal of Research in...· 0 citations
Pathogens represent a significant threat to aquaculture, with detrimental effects on the survival of farmed fish. To control these infections, copper sulfate (CuSO₄) has been used as a chemotherapeutic treatment. However, its use presents challenges, as the optimal concentration to minimize adverse health effects in certain species under production conditions remains poorly understood. The aim of this study was to evaluate the effects of acute copper sulfate toxicity on red tilapia (Oreochromis sp.) fry. To this end, 300 fry with an average total length of 2.9 ± 0.31 cm were acclimated for 15 days in a single 250-L tank. Fish were then randomly distributed into fifteen 20-L tanks and subjected to acute exposure for 96 h under five treatments: control, 0.5, 1.0, 2.0, and 4.0 mg/L CuSO₄. Histopathological evaluations were performed on the second gill arch to assess tissue alterations; identified abnormalities included lamellar fusion, congestion, hyperplasia, metaplasia, lamellar atrophy, and mucous cell proliferation. Although the low mortality observed across treatments precluded calculation of the median lethal concentration (LC50), increasing CuSO₄ concentration was associated with a progressive increase in both histological lesions and cumulative mortality, which reached 18 % in the highest exposure group. These findings demonstrate that copper sulfate can induce histopathological alterations in the gills and compromise survival at higher concentrations, underscoring the importance of understanding and mitigating the adverse effects of chemotherapeutic treatments in aquaculture, particularly in species such as red tilapia.
Andrés J. Bonilla-Reyes, Jonathan F. Villamil-Rodríguez, Jonny Andrés Yepes Blandón et al.· Intropica· 0 citations
Background: Mancozeb and propiconazole are widely used agricultural fungicides that can enter freshwater bodies through surface runoff and may affect non-target aquatic organisms. Clarias batrachus, a freshwater catfish of ecological and food-fish significance, is frequently associated with habitats exposed to agricultural effluents and provides a suitable model for cytogenetic assessment because of its nucleated erythrocytes. This study protocol outlines an approach for assessing the genotoxic potential of mancozeb and propiconazole, individually and in combination, in C. batrachus. The proposed design includes acute and chronic exposure scenarios, sub-lethal concentrations derived from LC₅₀ values, and biomarker-based evaluation of DNA damage in blood, gill, liver and kidney tissues. The principal endpoints include the alkaline comet assay, micronucleus test and chromosomal aberration analysis, supported by oxidative stress markers such as SOD, CAT, GPx and MDA. Molecular analysis of DNA repair and stress-response genes is also proposed to clarify possible mechanisms of toxicity. The protocol further emphasises environmentally relevant exposure conditions, mixture-toxicity assessment and standardised sampling procedures. The expected outcome is a structured framework for generating species-specific evidence on fungicide-induced genotoxicity in C. batrachus. Such data may support aquatic biomonitoring, ecological risk assessment and future management of pesticide contamination in freshwater environments.
Tanya, Neeru Singh· Asian Journal of Fisheries a...· 0 citations
Molecular insights are offered into the molecular defense mechanisms of L. vannamei against A. pacificum toxicity as well as enriched pathways including lysosome, C‑type lectin receptor signaling, peroxisome, drug metabolism, and neuroactive ligand‑receptor interactions.
Fuyuan Zeng, Haiming Chen, Huijie Yang et al.· PLoS ONE· 0 citations
