Ultrastructural changes in the digestive tract of Deroceras reticulatum (Müller) induced by a carbamate molluscicides and by metaldehyde

Electron microscope investigations reveal different reactions of cells in the digestive tract of Deroceras reticulatum to intoxication with carbamate or metaldehyde molluscicides. All enterocytes are more strongly attacked by the carbamate compound Mesurol than by metaldehyde. The better efficiency of Mesurol is primarily attributed to its severe impact on nuclei, leading to other cell damage and finally to an increased macrophage reaction. Metaldehyde leaves the enterocyte functions more or less intact except for that of mucus cells. It activates mucus extrusion immediately after the onset of intoxication. This mucus serves to dilute the toxin, which passes through the digestive tract and is voided. The severe attack of metaldehyde on the immature mucus cells results in cessation of mucus production, leading to a fatal mucus deficiency in the digestive tract

SchussenAktivplus: reduction of micropollutants and of potentially pathogenic bacteria for further water quality improvement of the river Schussen, a tributary of Lake Constance, Germany

The project focuses on the efficiency of combined technologies to reduce the release of micropollutants and bacteria into surface waters via sewage treatment plants of different size and via stormwater overflow basins of different types. As a model river in a highly populated catchment area, the river Schussen and, as a control, the river Argen, two tributaries of Lake Constance, Southern Germany, are under investigation in this project. The efficiency of the different cleaning technologies is monitored by a wide range of exposure and effect analyses including chemical and microbiological techniques as well as effect studies ranging from molecules to communities

Do contaminants originating from state-of-the-art treated wastewater impact the ecological quality of surface waters?

Since the 1980s, advances in wastewater treatment technology have led to considerably improved surface water quality in the urban areas of many high income countries. However, trace concentrations of organic wastewater-associated contaminants may still pose a key environmental hazard impairing the ecological quality of surface waters. To identify key impact factors, we analyzed the effects of a wide range of anthropogenic and environmental variables on the aquatic macroinvertebrate community. We assessed ecological water quality at 26 sampling sites in four urban German lowland river systems with a 0–100% load of state-of-the-art biological activated sludge treated wastewater. The chemical analysis suite comprised 12 organic contaminants (five phosphor organic flame retardants, two musk fragrances, bisphenol A, nonylphenol, octylphenol, diethyltoluamide, terbutryn), 16 polycyclic aromatic hydrocarbons, and 12 heavy metals. Non-metric multidimensional scaling identified organic contaminants that are mainly wastewater-associated (i.e., phosphor organic flame retardants, musk fragrances, and diethyltoluamide) as a major impact variable on macroinvertebrate species composition. The structural degradation of streams was also identified as a significant factor. Multiple linear regression models revealed a significant impact of organic contaminants on invertebrate populations, in particular on Ephemeroptera, Plecoptera, and Trichoptera species. Spearman rank correlation analyses confirmed wastewater-associated organic contaminants as the most significant variable negatively impacting the biodiversity of sensitive macroinvertebrate species. In addition to increased aquatic pollution with organic contaminants, a greater wastewater fraction was accompanied by a slight decrease in oxygen concentration and an increase in salinity. This study highlights the importance of reducing the wastewater-associated impact on surface waters. For aquatic ecosystems in urban areas this would lead to: (i) improvement of the ecological integrity, (ii) reduction of biodiversity loss, and (iii) faster achievement of objectives of legislative requirements, e.g., the European Water Framework Directive

The importance of mucus production in slugs' reaction to molluscicides and the impact of molluscicides on the mucus producing system

In Deroceras reticulatum, mucus cell ultrastructure and the histochemistry of the epidermis and the digestive tract epithelia were shown to be influenced by carbamate and metaldehyde, two molluscicides used as both contact and oral toxins. After carbamate poisoning mucus production is increased and the chemical composition of the slime is modified. Ultrastructural damage is less intense than after metaldehyde poisoning. After metaldehyde application mucus secretion is activated immediately and the production of mucus is prevented by the severe effect of this chemical, especially on undifferentiated mucus cells

Impact of a Wastewater Treatment Plant Upgrade on Amphipods and Other Macroinvertebrates: Individual and Community Responses

In the present study, we investigated the efficiency of additional wastewater treatment based on powdered activated carbon and its benefit for the ecosystem of a connected river system in the catchment area of Lake Constance, Southern Germany. We focused on the overall health status of gammarids and the integrity of the macrozoobenthic community. Samples were taken up- and down-stream of a wastewater treatment plant (WWTP), as well as before and after its upgrading. The investigations showed that both sex ratio and fecundity of gammarids, as well as the macrozoobenthic community were affected by the effluent prior to the WWTP upgrade. After the upgrade, gammarids from the downstream site did not differ any longer from those collected upstream of the WWTP with respect to the investigated health parameters. Furthermore, the overall number of taxa and, particularly, the number of sensitive taxa within the macrozoobenthic community downstream of the WWTP increased considerably. Therefore, we conclude that the additional treatment with powdered activated carbon was highly efficient to improve invertebrate health and community integrity

Impact of the Antidiabetic Drug Metformin and Its Transformation Product Guanylurea on the Health of the Big Ramshorn Snail (Planorbarius corneus)

Pharmaceuticals can enter surface waters via sewage treatment plants. In the environment, the substances and their transformation products, formed by the degradation of the parent compounds, can affect aquatic wildlife, including freshwater invertebrates. However, research on pharmaceutical-induced effects in wild freshwater organisms other than fish is still scarce. In our study, we investigated the impact of the highly consumed antidiabetic drug metformin and its main transformation product, guanylurea, on the health of a freshwater gastropod—the big ramshorn snail (Planorbarius corneus) by analysing its biochemical and cellular stress responses and apical parameters. The snails were exposed to different concentrations of the drug (0, 0.01, 0.1, 1, and 10 mg/L) and its transformation product (0, 0.1, 10, and 100 mg/L). The examined parameters were mortality, weight, tissue integrity of the hepatopancreas, and the levels of stress proteins and lipid peroxides. Mortality and the levels of stress proteins and lipid peroxides were not influenced by the two substances. In response to the highest concentrations of both chemicals, the weight of the snails was slightly but not significantly reduced. The histopathological investigation of the hepatopancreas revealed a significant effect of guanylurea at a concentration of 100 mg/L with an increased number of symptoms of cellular responses in the tissue (e.g., dilated lumen, disturbed compartmentation of the digestive cells, nucleus deformation, hyperplasia, and hypertrophy of crypt cells). For the parent compound, a similar trend was also observed for the highest concentration. Overall, the observed effects did not occur at environmentally relevant concentrations, but at concentrations which were 10,000 times higher than these. Thus, the results did not give rise to a major concern that metformin and guanylurea could pose a risk to the big ramshorn snail in the environment

Slugs as target or non-target organisms for environmental chemicals

The ability of slugs (Deroceras reticulatum) to survive exposure to various chemical stressors such as molluscicides ( carbamates, metaldehyde, ironchelates) or other environmental pollutants (heavy metals, pesticides) was investigated using x-ray analyses, autoradiography, filter electron microscopy, enzyme histochemistry, enzymatics, electron microscopy, and stress protein analyses. Uptake pathways, target sites, modes of action and general responses in the animals were studied, and the results (including aspects of resorption and metabolism of the toxins as well as their cellular and biochemical effects) interpreted in terms of both molluscicidal efficiency and of the consequences to slugs' ecological role as soil decomposers

Antioxidant defense and stress protein induction following heat stress in the Mediterranean snail<i>Xeropicta derbentina</i>[Pulmonata, Hygromiidae]

AbstractThe Mediterranean snail Xeropicta derbentina, being highly abundant in Southern France, has the need for efficient physiological adaptations to desiccation and over-heating posed by dry and hot environmental conditions. In consequence of heat, oxidative stress manifests in these organisms, which, in turn, leads to the formation of reactive oxygen species (ROS). In this study, we focused on adaptations on the biochemical level by investigation of antioxidant defenses and heat shock protein 70 (Hsp70) induction, both essential mechanisms of the heat stress response. We exposed snails to elevated temperature (25, 38, 40, 43, and 45°C) in the laboratory and measured the activity of the antioxidant enzymes catalase (CAT) and glutathione peroxidase (GPx), determined the Hsp70 level, and quantified lipid peroxidation. In general, we found a high constitutive level of CAT activity in all treatments, which may be interpreted as a permanent protection against ROS, i.e. hydrogen peroxide. CAT and GPx showed temperature-dependent activities: CAT activity was significantly increased in response to high temperatures (43 and 45°C), whereas GPx exhibited a significantly increased activity at 40°C, likely in response to high levels of lipid peroxides which already occurred in the 38°C treatment. Hsp70 showed a maximum induction at 40°C, followed by a decrease at higher temperatures. Our results reveal that X. derbentina possesses a set of efficient mechanisms to cope with damaging effects by heat. Furthermore, we could demonstrate that, beside the well documented Hsp70 stress response, the antioxidant defense plays a crucial role in these snails competence to survive extreme temperatures.</jats:p

Does the antidiabetic drug metformin affect embryo development and the health of brown trout (Salmo trutta f. fario)?

Abstract Background Due to the rising number of type 2 diabetes patients, the antidiabetic drug, metformin is currently among those pharmaceuticals with the highest consumption rates worldwide. Via sewage-treatment plants, metformin enters surface waters where it is frequently detected in low concentrations (µg/L). Since possible adverse effects of this substance in aquatic organisms have been insufficiently explored to date, the aim of this study was to investigate the impact of metformin on health and development in brown trout (Salmo trutta f. fario) and its microbiome. Results Brown trout embryos were exposed to 0, 1, 10, 100 and 1000 µg/L metformin over a period from 48 days post fertilisation (dpf) until 8 weeks post-yolk sac consumption at 7 °C (156 dpf) and 11 °C (143 dpf). Chemical analyses in tissues of exposed fish showed the concentration-dependent presence of metformin in the larvae. Mortality, embryonic development, body length, liver tissue integrity, stress protein levels and swimming behaviour were not influenced. However, compared to the controls, the amount of hepatic glycogen was higher in larvae exposed to metformin, especially in fish exposed to the lowest metformin concentration of 1 µg/L, which is environmentally relevant. At higher metformin concentrations, the glycogen content in the liver showed a high variability, especially for larvae exposed to 1000 µg/L metformin. Furthermore, the body weight of fish exposed to 10 and 100 µg/L metformin at 7 °C and to 1 µg/L metformin at 11 °C was decreased compared with the respective controls. The results of the microbiome analyses indicated a shift in the bacteria distribution in fish exposed to 1 and 10 µg/L metformin at 7 °C and to 100 µg/L metformin at 11 °C, leading to an increase of Proteobacteria and a reduction of Firmicutes and Actinobacteria. Conclusions Overall, weight reduction and the increased glycogen content belong to the described pharmaceutical effects of the drug in humans, but this study showed that they also occur in brown trout larvae. The impact of a shift in the intestinal microbiome caused by metformin on the immune system and vitality of the host organism should be the subject of further research before assessing the environmental relevance of the pharmaceutical