Morpho-Functional Alterations in the Gills of a Seawater Teleost, the Ornate Wrasse (Thalassoma pavo L.), after Short-Term Exposure to Chlorpyrifos

Toxic effects of chlorpyrifos on biochemical composition, enzyme activity and gill surface ultrastructure of three species of small fishes from India

The effects of chlorpyrifos, a frequently detected organophosphate in aquatic ecosystems, on biochemical (protein and glycogen) contents and oxidative enzyme activities (catalase and lipid peroxidation) in liver, muscle and gill tissues of three freshwater fish Trichogaster fasciata, Mystus vittatus and Heteropneustes fossilis were evaluated after 21-day exposure to 1 and 10% of 96 h LC50 of this pesticide, which were 1.63 and 16.3 µg L-1; 5.87 and 58.7 µg L-1 and 2.12 and 21.2 µg L-1, respectively. On comparing with control, significant reductions in protein concentration were found in liver, muscle and gill of the three fishes treated with both higher as well as lower concentrations of the pesticide except in gill of M. vittatus and liver of H. fossilis treated with the lower concentrations. Glycogen content reductions were significant in the liver and muscle of the fishes, as well as gill tissue of T. fasciata treated with the two pesticide concentrations. Significant elevations of catalase activity were found in liver of the three fishes treated with the higher concentrations, in muscle tissues of both T. fasciata and M. vittatus treated with both the concentrations and in gills of the three fishes except H. fossilis treated with the lower concentration of the pesticide. Significant elevations of lipid peroxidation level were also found in liver of all the three fish species treated with the higher concentrations, in the muscle tissue of M. vittatus as well as in the gill of T. fasciata and H. fossilis treated with both the concentrations of the pesticide. Chlorpyrifos exposed gill ultrastructure of T. fasciata, M. vittatus and H. fossilis revealed concentration-dependent effects of the pesticide on gill surface ultrastructure which include distortion of primary and secondary lamellae, deterioration of pavement cell and microridge structures, extrusion of red blood cells (RBCs), secretion of mucous layer on filament, sloughing of primary lamellae and clumping of secondary lamellae. The present study parameters could serve as useful biomarkers for evaluating the risk of pesticide toxicity to fish. These findings also point out the possible health risks to the consumers of these fish captured from contaminated water bodies.

Urtica dioica Extract Abrogates Chlorpyrifos-Induced Toxicity in Zebrafish Larvae

Chlorpyrifos (CPF) is a widely used organophosphate insecticide, though its excessive use causes environmental contamination, raising concerns about its adverse effects on human health. In this regard, Urtica dioica stands out as a promising candidate for counteracting chemical 'contaminant' toxicity thanks to its therapeutic properties. Therefore, our study aimed to investigate the potential of an Urtica dioica ethanolic extract (UDE) to mitigate chlorpyrifos-induced toxicity. Eight compounds in the Urtica dioica ethanolic extract have been identified, most of which present significant potential as antioxidant, anti-inflammatory, and neuroprotective agents. Chlorpyrifos exposure altered hatching rates, increased the incidence of teratogenic effects, and upregulated the expression of brain-derived neurotrophic factor (Bdnf) in zebrafish larvae telencephalon. On the other hand, UDE demonstrated a preventive effect against CPF-induced teratogenicity, which is expressed by a lower morphological deformity rate. Moreover, the UDE showed a rather protective effect, maintaining the physiological condition of the telencephalon. Additionally, CPF altered the locomotor behavior of larvae, which was characterized by irregular swimming and increased activity. This defective behavioral pattern was slightly attenuated by the UDE. Our findings suggest that the UDE possesses significant protective properties against CPF-induced toxicity, probably conferred by its natural antioxidant and anti-inflammatory contents. Still, further research is needed to elucidate the recruited mechanisms and implicated pathways on UDE's protective effects.

Short-term effects of the strobilurin fungicide dimoxystrobin on zebrafish gills: A morpho-functional study

Strobilurins represent the most widely used class of fungicides nowadays andare considered relatively non-toxic to mammals and birds but highly toxic to aquatic biota. Dimoxystrobin is one of the novel strobilurins, recently included in the 3rd Watch List of the European Commission as available data indicate that it could pose a significant risk to aquatic species. As yet, the number of studies explicitly assessing the impact of this fungicide on terrestrial and aquatic species is extremely low, and the toxic effects of dimoxystrobin on fish have not been reported. Here we investigate for the first time the alterations induced by two environmentally relevant and very low concentrations of dimoxystrobin (6.56 and 13.13 μg/L) in the fish gills. morphological, morphometric, ultrastructural, and functional alterations have been evaluated using zebrafish as a model species. We demonstrated that even short-term exposure (96 h) to dimoxystrobin alters fish gills reducing the surface available for gas exchange and inducing severe alterations encompassing three reaction patterns: circulatory disturbance and both regressive and progressive changes. Furthermore, we revealed that this fungicide impairs the expression of key enzymes involved in osmotic and acid-base regulation (Na⁺/K⁺-ATPase and AQP3) and the defensive response against oxidative stress (SOD and CAT). The information presented here highlights the importance of combining data from different analytical methods for evaluating the toxic potential of currently used and new agrochemical compounds. Our results will also contribute to the discussion on the suitability of mandatory ecotoxicological tests on vertebrates before the introduction on the market of new compounds.

Effects of trichlorfon organophosphate on the morphology of the gills and liver of Pseudoplatystoma corruscans

Possible changes in the morphology of the gills and liver of P. corruscans after exposure to TCF were evaluated. The fish were distributed into five groups in triplicate (n = 10 in each group: 0.0; 0.125; 0.25; 0.5; 1.0 mg/L of the commercial product NEGUVON®, for 96 h. TCF induced a high histopathological index associated with circulatory disorders (congestion and aneurysm), as well as progressive changes (lamellar hyperplasia, capillary dilation, epithelial detachment and edema) at the highest concentrations (0.25; 0.5 and 1.0 mg/L). In addition to the histopathological disturbances, there was an increase in the levels of neutral glycoproteins and alterations in the histomorphometry of the secondary lamellae (total height, apical region, median, basal and interlamellar) at the highest concentrations. In the liver, the alterations were more intensified, in addition to circulatory (congestion) and regressive disturbances (loss of hepatocyte architecture and accumulation of intracellular substances), progressive alterations (focal necrosis) were observed, indicating a high degree of hepatic tissue involvement. The results indicate that the use of TCF concentrations above 0.25 mg/L promotes histopathological, histomorphometric and histochemical changes in the gills and liver of P. corruscans, imposing a biological risk that affects the aquatic environment and the health of fish.