Impact of glyphosate-based herbicide on early embryonic development of the amphibian Xenopus laevis

Effects of glyphosate on neurotoxicity, oxidative stress and immune suppression in red swamp crayfish, Procambarus Clarkii

Glyphosate, a prevalent herbicide, has raised concerns due to its potential ecological impact, especially on aquatic ecosystems. While it is crucial for managing agricultural productivity, its inadvertent effects on non-target aquatic species like the red swamp crayfish, Procambarus clarkii, are not fully understood. In the present study, the neurotoxicity, oxidative stress, and immune suppression of glyphosate on P. clarkii were investigated. Sublethal glyphosate exposure (5, 10 and 20 mg/L) for 96 h was found to significantly decrease AChE activity in both brain and hepatopancreas, correlating with reduced foraging efficiency and increased turnover time. Oxidative stress was evident through increased lipid peroxidation (LPO) and malondialdehyde (MDA) levels and altered antioxidant enzyme activities such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). In addition, the total antioxidative capacity (T-AOC) was inhibited at 10 and 20 mg/L of glyphosate exposure. Immune assays revealed a decrease in total hemocyte counts (THC) and suppression of key immune enzyme activities and transcriptional expressions at higher concentrations, suggesting compromised immune defenses. The findings demonstrate that glyphosate can induce considerable neurotoxic and immunotoxic effects in P. clarkii, disrupting essential physiological functions and behavior.

Comparing the effects of three neonicotinoids on embryogenesis of the South African clawed frog Xenopus laevis

Neonicotinoids (NEOs) are widely used insecticides that are ubiquitous in agricultural use. Since NEOs are found in natural waters as well as in tap water and human urine in regions where NEOs are widely used, NEOs pose a potential hazard to non-target organisms such as animals and humans. Some of the commonly detected NEOs are imidacloprid (IMD), thiamethoxam (TMX), and its metabolite clothianidin (CLO). Although previously published scientific information, including an assessment of the environmental risks, particularly for bees, had resulted in a ban on the outdoor use of these three NEOs in the EU - their use is now only permitted in closed greenhouses - these NEOs continue to be used in agriculture in many other parts of the world. Therefore, a detailed study and comparison of the effects of NEOs on the embryonic development of non-target organisms is needed to further define the risk profiles. Embryos of the South African clawed frog Xenopus laevis, a well-established aquatic model, were exposed to different concentrations of IMD, TMX, or CLO (0.1-100 mg/L) to study and compare the possible effects of a single contaminant in natural water bodies on early embryogenesis. The results included a reduced body length, a smaller orbital space, impaired cranial cartilage and nerves, and an altered heart structure and function. At the molecular level, NEO exposure partially resulted in an altered expression of tissue-specific factors, which are involved in eye, cranial placode, and heart development. Our results suggest that the NEOs studied negatively affect the embryonic development of the non-target organism X. laevis. Since pesticides, especially NEOs, pollute the environment worldwide, it is suggested that they are strictly controlled and monitored in the areas where they are used. In addition, the question arises as to whether pesticide metabolites also pose a risk to the environment and need to be investigated further so that they can be taken into account when registering ingredients.

Polyoxyethylene tallow amine and glyphosate exert different developmental toxicities on human pluripotent stem cells-derived heart organoid model

The early stage of heart development is highly susceptible to various environmental factors. While the use of animal models has aided in identifying numerous environmental risk factors, the variability between species and the low throughput limit their translational potential. Recently, a type of self-assembling cardiac structures, known as human heart organoids (hHOs), exhibits a remarkable biological consistency with human heart. However, the feasibility of hHOs for assessing cardiac developmental risk factors remains unexplored. Here, we focused on the cardiac developmental effects of core components of Glyphosate-based herbicides (GBHs), the most widely used herbicides, to evaluate the reliability of hHOs for the prediction of possible cardiogenesis toxicity. GBHs have been proven toxic to cardiac development based on multiple animal models, with the mechanism remaining unknown. We found that polyoxyethylene tallow amine (POEA), the most common surfactant in GBHs formulations, played a dominant role in GBHs' heart developmental toxicity. Though there were a few differences in transcriptive features, hHOs exposed to sole POEA and combined POEA and Glyphosate would suffer from both disruption of heart contraction and disturbance of commitment in cardiomyocyte isoforms. By contrast, Glyphosate only caused mild epicardial hyperplasia. This study not only sheds light on the toxic mechanism of GBHs, but also serves as a methodological demonstration, showcasing its effectiveness in recognizing and evaluating environmental risk factors, and deciphering toxic mechanisms.

Glyphosate without Co-formulants affects embryonic development of the south african clawed frog Xenopus laevis

BACKGROUND

Glyphosate (GLY) is the most widely used herbicide in the world. Due to its mode of action as an inhibitor of the 5-enolpyruvylshikimate-3-phosphate synthase, an important step in the shikimate pathway, specifically in plants, GLY is considered to be of low toxicity to non-target organisms. However, various studies have shown the negative effects of GLY on the mortality and development of different non-target organisms, including insects, rodents, fish and amphibians. To better understand the various effects of GLY in more detail, we studied the effects of GLY without co-formulants during the embryogenesis of the aquatic model organism Xenopus laevis.

RESULTS

A treatment with GLY affected various morphological endpoints in X. laevis tadpoles (body length, head width and area, eye area). Additionally, GLY interfered with the mobility as well as the neural and cardiac development of the embryos at stage 44/45. We were able to detect detailed structural changes in the cranial nerves and the heart and gained insights into the negative effects of GLY on cardiomyocyte differentiation.

CONCLUSION

The application of GLY without co-formulants resulted in negative effects on several endpoints in the early embryonic development of X. laevis at concentrations that are environmentally relevant and concentrations that reflect the worst-case scenarios. This indicates that GLY could have a strong negative impact on the survival and lives of amphibians in natural waters. As a result, future GLY approvals should consider its impact on the environment.

The neonicotinoid thiacloprid leads to multiple defects during early embryogenesis of the South African clawed frog (Xenopuslaevis)

There is increasing concern about the health effects of pesticides that pollute natural waters. In particular, the use of neonicotinoids, such as thiacloprid (THD), is causing unease. THD is considered non-toxic to non-target vertebrates. Studies classify THD as carcinogenic, toxic to reproduction, and therefore harmful to the environment. A detailed study of possible THD effects during the amphibian embryogenesis is needed because leaching can introduce THD into aquatic environments. We incubated stage 2 embryos of the South African clawed frog in various THD concentrations (0.1-100 mg/L) at 14 °C to study the potential effects of a one-time THD contamination of waters on the early embryogenesis. We showed that THD has, indeed, negative effects on the embryonic development of the X. laevis. A treatment with THD led to a reduced embryonic body length and mobility. Furthermore, a treatment with THD resulted in smaller cranial cartilages, eyes and brains, and the embryos had shorter cranial nerves and an impaired cardiogenesis. On a molecular basis, THD led to a reduced expression of the brain marker emx1 and the heart marker mhcα. Our results underly the importance of a strict and efficient monitoring of the regulatory levels and application areas of THD.

Molecular and Histological Effects of Glyphosate on Testicular Tissue of the Lizard Podarcis siculus

The expansion of agriculture produces a steady increase in habitat fragmentation and degradation due to the increased use of pesticides and herbicides. Habitat loss and alteration associated with crop production play an important role in reptile decline, among which lizards are particularly endangered. In this study, we evaluated testicular structure, steroidogenesis, and estrogen receptor expression/localization after three weeks of oral exposure to glyphosate at 0.05 and 0.5 μg/kg body weight every other day in the field lizard Podarcis siculus. Our results show that glyphosate affected testicular morphology, reduced spermatogenesis, altered gap junctions and changed the localization of estrogen receptors in germ cells, increasing their expression; the effects were mostly dose-dependent. The result also demonstrates that glyphosate, at least at these concentrations, did not influence steroidogenesis. Overall, the data indicate that this herbicide can disturb the morphophysiology of the male lizard's reproductive system, with obviously detrimental effects on their reproductive fitness. The effects of glyphosate must be considered biologically relevant and could endanger the reproductive capacity not only of lizards but also of other vertebrates, including humans; a more controlled and less intensive use of glyphosate in areas devoted to crop production would therefore be advisable.

Anuran heart development and critical developmental periods: a comparative analysis of three Neotropical anuran species

The heart begins to form early during vertebrate development and is the first functional organ of the embryo. This study aimed to describe and compare the heart development in three Neotropical anuran species, Physalaemus albonotatus, Elachistocleis bicolor, and Scinax nasicus. Different Gosner Stages (GS) of embryos (GS 18-20) and premetamorphic (GS 21-25), prometamorphic (GS 26-41) and metamorphic (GS 42-46) tadpoles were analyzed using stereoscopic microscopy and Scanning Electronic Microscopy. Heart development was similar in the three analyzed species; however, some heterochronic events were identified between P. albonotatus and S. nasicus compared to E. bicolor. In addition, different patterns of melanophores arrangement were observed. During the embryonic and metamorphic periods, the main morphogenetic events occur: formation of the heart tube, regionalization of the heart compartments, development of spiral valve, onset of heartbeat, looping, and final displacement of the atrium and its complete septation. Both periods are critical for the normal morphogenesis and the correct functioning of the anuran heart. These results are useful to characterize the normal anuran heart morphology and to identify possible abnormalities caused by exposure to environmental contaminants.