Browsing by Author "Soares, Amadeu M. V. M."
Now showing 1 - 5 of 5
Results Per Page
Sort Options
- Amitraz toxicity to the midge Chironomus riparius: Life-history and biochemical responsesPublication . Monteiro, Hugo R.; Lemos, Marco F. L.; Novais, Sara C.; Soares, Amadeu M. V. M.; Pestana, João L. T.Acute and chronic toxicity of the formamidine pesticide amitraz to the midge Chironomus riparius was assessed using conventional ecotoxicological tests and biochemical approaches (biomarkers). Amitraz is mainly used as an ectoparasiticide in veterinary medicine, but also in agriculture and apiculture. However, information of amitraz toxicity to non-target invertebrates is limited. Besides the impairment of developmental and emergence rates (reduced larval growth, emergence, and delayed development time) caused by chronic exposure to amitraz, acute exposures induced alterations in the antioxidant enzymes glutathione peroxidase (GPx) and catalase (CAT), and in energetic metabolism biomarkers, lactate dehydrogenase (LDH) and electron transport system (ETS) activities. Moreover, lipid peroxidation (LPO) increased by amitraz exposure. Our results reveal potential secondary effects of amitraz to invertebrates and biomarkers that may aid in the interpretation of sub-lethal toxic responses to amitraz. These results add information concerning the potential outcomes of amitraz exposure to freshwater invertebrates underlining the importance of risk assessment studies of formamidine pesticides.
- Assessment of fipronil toxicity to the freshwater midge Chironomus riparius: Molecular, biochemical, and organismal responsesPublication . Monteiro, Hugo R.; Pestana, João L. T.; Novais, Sara C.; Leston, Sara; Ramos, Fernando; Soares, Amadeu M. V. M.; Devreese, Bart; Lemos, Marco F. L.Fipronil is a phenylpyrazole insecticide that entered the market to replace organochlorides and organophosphates. Fipronil impairs the regular inhibition of nerve impulses that ultimately result in paralysis and death of insects. Because of its use as a pest control, and due to runoff events, fipronil has been detected in freshwater systems near agricultural areas, and therefore might represent a threat to non-target aquatic organisms. In this study, the toxicity of fipronil to the freshwater midge Chironomus riparius was investigated at biochemical, molecular, and whole organism (e.g. growth, emergence, and behavior) levels. At the individual level, chronic (28 days) exposure to fipronil resulted in reduced larval growth and emergence with a lowest observed effect concentration (LOEC) of 0.081 μg L−1. Adult weight, which is directly linked to the flying performance and fecundity of midges, was also affected (LOEC = 0.040 μg L−1). Additionally, behavioral changes such as irregular burrowing behavior of C. riparius larvae (EC50 = 0.084 μg L−1) and impairment of adult flying performance were observed. At a biochemical level, acute (48 h) exposure to fipronil increased cellular oxygen consumption (as indicated by the increase of electron transport system (ETS) activity) and decreased antioxidant and detoxification defenses (as suggested by the decrease in catalase (CAT) and glutathione S-transferase (GST) activities). Exposure to fipronil also caused alterations in the fatty acid profile of C. riparius, since high levels of stearidonic acid (SDA) were observed. A comparison between exposed and nonexposed larvae also revealed alterations in the expression of globins, cytoskeleton and motor proteins, and proteins involved in protein biosynthesis. These alterations may aid in the interpretation of potential mechanisms of action that lead to the effects observed at the organism level. Present results show that environmentally relevant concentrations of fipronil are toxic to chironomid populations which call for monitoring of phenylpyrazole insecticides and of their ecological effects in freshwaters. Present results also emphasize the importance of complementing ecotoxicological data with molecular approaches such as proteomics, for a better interpretation of the mode of action of insecticides in aquatic invertebrates.
- Fatty acid profile of the sea snail Gibbula umbilicalis as a biomarker for coastal metal pollutionPublication . Silva, Carla; Simões, Tiago; Novais, Sara C.; Pimparel, Inês; Granada, Luana; Soares, Amadeu M. V. M.; Barata, Carlos; Lemos, Marco F. L.Metals are among the most common environmental pollutants with natural or anthropogenic origin that can be easily transferred through the food chain. Marine gastropods are known to accumulate high concentrations of these metals in their tissues. Gibbula umbilicalis ecological importance and abundant soft tissues, which enables extent biochemical assessments, makes this particular organism a potentially suitable species for marine ecotoxicological studies. Fatty acids are carbon-rich compounds that are ubiquitous in all organisms and easy to metabolize. Their biological specificity, relatively well-studied functions and importance, and the fact that they may alter when stress is induced, make fatty acids prospect biomarkers. This work aimed to assess fatty acid profile changes in the gastropod G. umbilicalis exposed to three metal contaminants. After a 168 h exposure to cadmium, mercury, and nickel, the following lipid related endpoints were measured: total lipid content; lipid peroxidation; and fatty acid profile (FAP). The analysis of the FAP suggested an alteration in the fatty acid metabolism and indicated a link between metals exposure and homeoviscous adaptation and immune response. In particular, five fatty acids (palmitic, eicosatrienoic, arachidonic, eicosapentaenoic, and docosahexaenoic acids), demonstrated to be especially good indicators of G. umbilicalis responses to the array of metals used, having thus the potential to be used as biomarkers for metal contamination in this species. This work represents a first approach for the use of FAP signature as a sensitive and informative parameter and novel tool in environmental risk assessment (ERA) of coastal environments, using G. umbilicalis as model species.
- Linking cholinesterase inhibition with behavioural changes in the sea snail Gibbula umbilicalis: Effects of the organophosphate pesticide chlorpyrifosPublication . Silva, Carla O.; Novais, Sara C.; Alves, Luís M. F.; Soares, Amadeu M. V. M.; Barata, Carlos; Lemos, Marco F. L.Inhibition of acetylcholinesterase (AChE) activity has been widely used to assess the exposure and effects of anticholinergic environmental contaminants in several species. The aim of this study was to investigate if sublethal concentrations of the organophosphorous pesticide chlorpyrifos (CPF), a well-known AChE inhibitor, would also affect cholinesterases (ChE) in Gibbula umbilicalis and if this inhibition would result in an alteration of its behaviour, in an attempt to link the effects observed at the cellular level with effects at higher levels of ecological relevance. The biochemical properties of ChEs in this species were first characterized through the assessment of different enzymatic forms present in the sea snail, using different substrates and selective inhibitors. The results suggest that G. umbilicalis possess ChEs with characteristics of typical AChE, which should be the main form present. Additionally, in vitro and in vivo effects of CPF on AChE activity were investigated, along with effects on snails' behaviour: the ability of the snails to move/turn after exposure to the contaminant (flipping test). As expected, CPF inhibited AChE activity both in vitro and in vivo conditions. Moreover, the link between AChE activity inhibition and adverse effects on behavioural changes was established: AChE inhibition was positively correlated with the flipping test, indicating a mechanistic relationship between the two endpoints determined in in vivo exposures. This study highlights the importance of linking biochemical endpoints such as AChE activity with higher level endpoints like behavioural alterations, increasing the ecological relevance of the effects observed.
- Toxicity of the insecticides spinosad and indoxacarb to the non-target aquatic midge Chironomus ripariusPublication . Monteiro, Hugo R.; Pestana, João L. T.; Novais, Sara C.; Soares, Amadeu M. V. M.; Lemos, Marco F. L.Spinosad and indoxacarb are two relatively new insecticides mainly used in agriculture to control insect pests. However, at their current application rates, non-target aquatic insect species may also be impacted. In this study, larvae of the non-biting midge Chironomus riparius were exposed in the laboratory to both insecticides and their effects evaluated at the organismal level, using standard ecotoxicological tests, and at the biochemical level, by monitoring specific oxidative stress, neuronal, and energy metabolism biomarkers. Chronic exposure to both insecticides compromised growth and emergence of C. riparius. Short-term exposures revealed alterations at biochemical level that might be related to the toxicological targets of both insecticides. Growth and development time were the most sensitive endpoints at individual level for both pesticides, while at the biochemical level, the electron transport system activity was the most sensitive biomarker for spinosad exposure, suggesting an increase in energy demands associated with the activation of defense mechanisms. Glutathione-S-transferase was the most sensitive biomarker for indoxacarb exposure, underlining the role of this enzyme in the detoxification of indoxacarb. Additionally, changes in lactate dehydrogenase and glutathione peroxidase activities were observed for both insecticides, and evidences of oxidative damage were found for spinosad. This study contributes to the growing knowledge on sublethal effects of novel insecticides on non-target aquatic invertebrates and strengthens the usefulness of biochemical biomarkers to support the interpretation of their potentially deleterious effects on aquatic insects near agricultural fields.