Abstract The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is widely used in tropical agriculture, yet its effects on non-target ectothermic vertebrates remain poorly understood. This study assessed the subchronic toxicological impact of 2,4-D on the liver and kidneys of Tropidurus torquatus , a neotropical lizard commonly found in agricultural areas. Seventeen adult males were divided into control ( n = 9) and treatment ( n = 8) groups. The treated group received 0.01 mg/kg body weight/day of 2,4-D orally for 30 days, based on the acceptable daily intake for mammals. Histopathological, stereological, and biochemical analyses were conducted. Hepatic histopathology showed no significant alterations, but stereology revealed a reduction in hepatocyte volume fraction in treated animals ( p < 0.05). Renal histopathology showed significant degenerative changes, including hydropic-vacuolar degeneration, coagulative necrosis, and accumulation of brownish granular pigment ( p < 0.0001). Biochemically, 2,4-D exposure triggered oxidative stress in both organs, with increased reactive oxygen species and lipid peroxidation, and reduced activities of superoxide dismutase and catalase. Despite these functional changes, renal stereology showed no significant differences in kidney volume or glomerular count. These findings indicate that even at doses considered safe for mammals, 2,4-D causes subclinical but relevant toxic effects in reptiles. This highlights the limitations of extrapolating mammalian safety thresholds to other taxonomic groups and reinforces the need for specific ecotoxicological assessments focused on tropical herpetofauna.
Approximately 1.6 million tons of conventional munitions were dumped in German coastal waters. Corrosion of munition shells facilitates the leakage of explosives, such as the toxic and carcinogenic 2,4,6-trinitrotoluene (TNT), into the marine environment. Consequently, TNT contamination was detected in seawater, sediments, and marine organisms near munition dump sites, and is known to cause adverse effects in marine organisms. Accordingly, avoidance of contaminated areas would be advantageous for fish. We therefore hypothesized that fish respond to dissolved TNT and exhibit an avoidance reaction. To test this, we exposed three-spined sticklebacks (Gasterosteus aculeatus) to environmentally relevant TNT concentrations and evaluated their behavioral response. Individual fish were placed in a behavioral test tank equipped with two hideout zones composed of artificial plants. The hideout zone occupied by the stickleback was infused with either TNT solution (100 µg/L) or control water. Behavioral readouts included the time stickleback spent in the infused hideout zone, time until the exposed hideout zone was first left, and number of transitions between hideout zones. Sticklebacks did not exhibit significant behavioral responses to environmentally relevant TNT exposure. Consequently, fish inhabiting munition dump sites may experience chronic TNT exposure, potentially increasing long-term toxicological risks.
Short-chain per- and polyfluoroalkyl substances (PFAS), including fluorinated acids, have expanded as replacements for legacy per- and polyfluoroalkyl substances, yet aquatic safety assumptions are challenged by emerging fish toxicity data and the realities of persistence and exposure. This review synthesizes fish toxicology evidence for three environmentally important short-chain fluorinated acids selected to represent distinct chemical and exposure contexts: perfluorohexanoic acid (PFHxA) as a short-chain perfluorocarboxylic acid, hexafluoropropylene oxide dimer acid (HFPO-DA) as an ether-based replacement compound, and trifluoroacetic acid (TFA) as an ultrashort terminal transformation product characterized by exceptional persistence and mobility. Across fish models, perfluorohexanoic acid is generally less bioaccumulative than many long-chain analogs, but can still elicit biologically meaningful neurobehavioral and molecular alterations depending on life stage and exposure scenario. Hexafluoropropylene oxide dimer acid, widely known as a replacement for perfluorooctanoic acid, shows patterns consistent with endocrine and metabolic disturbance in fish development, including thyroid-axis–related endpoints and transcriptomic or metabolomic disruptions. Trifluoroacetic acid differs fundamentally: it is extremely persistent and highly mobile, with evidence of increasing environmental burdens and unresolved thresholds for long-term ecological effects. The comparison is further interpreted in the context of other short-chain perfluorocarboxylic acids, particularly PFBA, PFPeA, and PFHpA, to clarify the position of the selected compounds within the broader short-chain PFAS spectrum. Overall, the comparison shows that short-chain fluorinated acids should not be interpreted through a single safety gradient, because PFHxA, HFPO-DA, and TFA represent distinct but connected risk logics shaped by exposure persistence, internal-dose dynamics, and pathway-specific biological responses. Future priorities include harmonized exposure verification, tissue-dose reporting, mixture-relevant designs, and cross-life-stage endpoints that better predict population-relevant outcomes.
Glyphosate, one of the most widely used herbicides globally, is a significant environmental contaminant that may affect non-target organisms crucial to ecosystem services, including biological pest control. While glyphosate targets the shikimate pathway in plants, which is absent in animals, there is increasing evidence that glyphosate induces sublethal effects on arthropod predators. However, the factors modulating these effects remain unclear. Here, we investigated how physiological context, specifically pre-treatment with the broad-spectrum antibiotic tetracycline, commonly used to experimentally alter host associated microbial communities, modulates the sublethal hazard of glyphosate-based herbicide (GBH) on the predatory behavior of adult female Pardosa wolf spiders. Predation efficiency was measured using functional response assays across varying prey densities. Our results showed that GBH significantly reduced the spiders’ predation rates, confirming its sublethal toxicity. However, spiders pre-treated with antibiotics exhibited higher capture rates following GBH exposure compared to the GBH only group. These findings demonstrate that the sublethal hazard of GBH on predators is context-dependent and can be altered by antibiotic-sensitive processes (such as host-symbiont interactions). This study highlights the complexity of pesticide effects on ecosystem services and suggests that the functional response of non-target predators depends strongly on their physiological background.
Aquatic organisms in eutrophic brackish and freshwater systems are chronically exposed to natural and anthropogenic contaminants, including cyanotoxins, metals and pesticides, mainly driven by cyanobacterial blooms and human activities. However, the environmental risks posed by their combinations to the aquatic environment remain poorly understood. This study investigated the growth response of Chlorella vulgaris exposed to four single-chemical compounds (microcystin-LR, cylindrospermopsin, terbuthylazine, and cadmium) and five binary mixtures for 7 days. In single-chemical exposures, terbuthylazine was the most toxic to C. vulgaris, followed by cadmium, cylindrospermopsin and microcystin-LR. The obtained growth data were compared with concentration addition predictions based on individual toxicities using the MIXTOX tool, testing deviations for synergistic/antagonistic interactions, dose ratio and dose level dependencies. Mixture effects varied with composition and exposure time. Antagonism was the prevailing type of interaction between the chemical compounds after 4 days of exposure, while dose level dependency was the only deviation observed after 7 days. Regarding dose level dependency, synergism was observed at low doses of each chemical in three of the five tested binary mixtures. Time was an important factor in the change in the toxicity pattern. This synergistic effect poses a significant risk to aquatic organisms exposed simultaneously to cyanotoxins and anthropogenic contaminants in the environment.
