First evidence of transcriptional modulation by chlorothalonil in mussels Perna perna

The toxicity and health risk of chlorothalonil to non-target animals and humans: A systematic review

Chlorothalonil (CTL), an organochloride fungicide applied for decades worldwide, has been found to be present in various matrixes and even accumulates in humans or other mammals through the food chain. Its high residue and diffusion in the environment have severely affected food security and public health. More and more research has considered CTL as a possible toxin to environmental non-target organisms, via influencing multiple systems such as metabolic, developmental, endocrine, genetic, and reproductive pathways. Aquatic organisms and amphibians are the most vulnerable species to CTL exposure, especially during the early period of development. Under experimental conditions, CTL can also have toxic effects on rodents and other non-target organisms. As for humans, CTL exposure is most often reported to be relevant to allergic reactions to the skin and eyes. We hope that this review will improve our understanding of the hazards and risks that CTL poses to non-target organisms and find a strategy for rational use.

Emerging and legacy contaminants on the Brazilian southern coast (Santa Catarina): A multi-biomarker approach in oysters Crassostrea gasar (Adanson, 1757)

Coastal environments, such as those in the Santa Catarina State (SC, Brazil), are considered the primary receptors of anthropogenic pollutants. In this study, our objective was to evaluate the levels of emerging contaminants (ECs) and persistent organic pollutants (POPs) in indigenous Crassostrea gasar oysters from different regions of SC coast in the summer season (March 2022). Field collections were conducted in the São Francisco do Sul, Itajaí, Florianópolis and Laguna coastal zones. We analyzed the bioaccumulation levels of 75 compounds, including antibiotics (AB), endocrine disruptors (ED), non-steroidal anti-inflammatory drugs (NSAIDs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and pesticides. Furthermore, we assessed biomarker responses related to biotransformation, antioxidant defense, heat shock protection and oxidative damage in oysters' gills. Prevalence of ECs was observed in the central and southern regions, while the highest concentrations of POPs were detected in the central-northern regions of SC. Oysters exhibited an induction in biotransformation systems (cyp2au1 and cyp356a1, sult and GST activity) and antioxidant enzymes activities (SOD, CAT and GPx). Higher susceptibility to lipid peroxidation was observed in the animals from Florianópolis compared to other regions. Correlation analyses indicated possible associations between contaminants and environmental variables in the biomarker responses, serving as a warning related to climate change. Our results highlight the influence of anthropogenic activities on SC, serving as baseline of ECs and POPs levels in the coastal areas of Santa Catarina, indicating more critical zones for extensive monitoring, aiming to conserve coastal regions.

Antifouling booster biocides in Latin America and the Caribbean: A 20-year review

This review summarized booster biocides studies from Latin America and the Caribbean during the last two decades. Studies were focused on six countries, with most of them in Brazil. In water and sediment, diuron and Irgarol were the most abundant and frequent biocides, probably due to their former intense use. Antifouling paint particles were also reported and had mainly DCOIT, which is currently the most used booster biocide. Toxicity of individual booster biocides was tested in laboratory, and most effects were related to chlorothalonil, DCOIT, dichlofluanid, and Irgarol, including, but not limited to DNA damage, fertility decrease, and mortality at different trophic levels. This review highlighted the need for further studies on environmental occurrence of booster biocides in Latin America and Caribbean associated to ecotoxicological studies. Such information is essential to determine the potential ecological risks and to create directives regarding safe limits of booster biocides in aquatic systems.

Ultrastructure of the gill ciliary epithelium of Limnoperna fortunei (Dunker 1857), the invasive golden mussel

Background

Limnoperna fortunei is a freshwater bivalve mollusc originally from southern Asia that invaded South America in the 1990’s. Due to its highly efficient water pumping and filtering, and its capacity to form strong adhesions to a variety of substrates by byssus thread, this invasive species has been able to adapt to several environments across South America, causing significant ecological and economic damages. By gaining a deeper understanding of the biological and ecological aspects of L. fortunei we will be able to establish more effective strategies to manage its invasion. The gills of the mollusc are key structures responsible for several biological functions, including respiration and feeding. In this work, we characterized the ultrastructure of L. fortunei gills and its ciliary epithelium using light microscopy, transmission and scanning electron microscopies. This is the first report of the morphology of the epithelial cells and cilia of the gill of L. fortunei visualized in high resolution.

Results

The analysis showed highly organized and abundant ciliary structures (lateral cilia, laterofrontal cirri and frontal cilia) on the entire length of the branchial epithelium. Mitochondria, smooth endoplasmic reticulum and glycogen granules were abundantly found in the epithelial cells of the gills, demonstrating the energy-demanding function of these structures. Neutral mucopolysaccharides (low viscosity mucus) were observed on the frontal surface of the gill filaments and acid mucopolysaccharides (high viscosity mucus) were observed to be spread out, mainly on the lateral tract. Spherical vesicles, possibly containing mucus, could also be observed in these cells. These findings demonstrate the importance of the mucociliary processes in particle capture and selection.

Conclusions

Our data suggest that the mechanism used by this mollusc for particle capture and selection could contribute to a better understanding of key aspects of invasion and also in the establishment of more efficient and economically viable strategies of population control.

Molecular and biochemical effects of the antifouling DCOIT in the mussel Perna perna

Biological fouling is an unwanted phenomenon that results in economic losses to the shipping industry. To prevent fouling, antifouling paints are used. DCOIT (4,5- dichloro-2-n-octyl-4-isothiazolin-3-one) is a biocide present in many antifouling paint formulations, and is toxic to a wide range of organisms. The aim of the present study was to evaluate the effects of DCOIT on oxidative stress indicators of the brown mussel, Perna perna. Molecular (SOD-like, GSTO-like and MGST-like mRNA levels) and biochemical (activities of superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST), and levels of glutathione (GSH), reactive oxygen species (ROS) and protein carbonyls (PCO)) components were evaluated. Further, levels of biomarkers were assessed in the gills and digestive glands of mussels. Bivalves were exposed to DCOIT (control, 0.1 μg/L and 10 μg/L) for up to 96 h. DCOIT exposure decreased GSH content in gills. Moreover, exposure to DCOIT also decreased CAT activity in the gills and digestive glands of mussels. GST activity increased in digestive gland after exposure for 24 h to both concentrations of DCOIT tested. SOD activity, ROS levels and PCO content were not affected by exposure to the contaminant. Regarding the molecular biomarkers evaluated, DCOIT exposure altered mRNA levels of SOD-like in both tissues after 24 and 96 h of exposure, and decreased MGST-like mRNA levels in the digestive gland after 96 h of exposure to the chemical. These findings suggested that exposure to DCOIT may alter the biochemical and molecular functioning of P. perna, which may harm the species.

Effects of DCOIT (4,5-dichloro-2-octyl-4-isothiazolin-3-one) to the haemocytes of mussels Perna perna

Bivalve molluscs rely only on an innate immune system to execute cellular and humoral processes. Haemocytes, the haemolymph circulating cells, play a major role in this type of immunity, principally regarding cellular defences. Considering that environmental pollutants can affect the immune system of invertebrates, this work evaluated the effects of the antifouling biocide 4,5-dicloro-2-n-octil-4-isotiazolin-3-ona (DCOIT) on the haemocytes of mussels Perna perna. Individuals were exposed to 0 (control), 0.1 μg L^-1 and 10 μg L^-1 of DCOIT for up to 96 h. The analysed parameters included: total (THC) and differential (DHC) haemocyte count, cellular viability, adhesion capacity, phagocytic activity, levels of reactive oxygen species and DNA damage. Moreover, the stress on stress (SOS) response of mussels was analysed as a general stress index. The results show that DCOIT increased the haemocyte adhesion capacity and caused a decrease in THC and in the haemocyte viability after 24 h of exposure. After 96 h of exposure, DCOIT only affected the haemocyte adhesion capacity, which was decreased by biocide exposure. Moreover, exposure to DCOIT for 96 h did not affect the capacity for air survival of mussels. These results indicate that DCOIT interferes in important parameters associated with the innate immunity of P. perna, mainly after 24 h of exposure. It is suggested that the animals were able to develop some compensatory response strategy, making them more resistant to the biocide.