Seasonal changes of two biomarkers of oxidative stress (LDH, MDA) in the edible mollusc Donax trunculus (Mollusca: Bivalvia) from the Gulf of Annaba (Algeria): correlation with carbohydrate and lipid contents

Holistic assessment of dimethoate toxicity in Carcinus aestuarii's muscle tissues

Dimethoate (DMT) is one of the most harmful and commonly used organophosphate pesticides in agricultural lands to control different groups of parasitic insects. However, this pesticide is considered a dangerous pollutant for aquatic organisms following its infiltration in coastal ecosystems through leaching. Yet, our investigation aimed to gain new insights into the toxicity mechanism of DMT in the muscles of the green crab Carcinus aestuarii, regarding oxidative stress, neurotransmission impairment, histological aspects, and changes in lipid composition, assessed for the first time on the green crab's muscle. Specimens of C. aestuarii were exposed to 50, 100, and 200 µg DMT L-1 for 24 h. Compared to the negative control group, the higher the DMT concentration, the lower the saturated fatty acids (SFA), and the higher the monounsaturated fatty acids (MUFA). The significant increase in polyunsaturated fatty acid n-6 (PUFA n-6) was related to the high release, mainly, of linoleic acid (LA, C18: 2n6) and arachidonic acid (ARA, C20: 4n6) levels. Biochemical biomarkers showed that DMT exposure promoted oxidative stress, highlighted by increased levels of hydrogen peroxide (H2O2), malondialdehyde (MDA), advanced oxidation protein product levels (AOPP), and protein carbonyl (PCO). Furthermore, the antioxidant defense system was activated, as demonstrated by the significant changes in the enzymatic activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and reduced glutathione (GSH) levels associated with an adaptation process of C. aestuarii to cope with the DMT exposure. This pesticide significantly impairs the neurotransmission process, as evidenced by the inhibition of acetylcholinesterase (AChE) activity. Finally, several histopathological changes were revealed in DMT-treated crabs, including vacuolation, and muscle bundle loss.This research offered new insights into the toxic mechanism of DMT, pointing to the usefulness of fatty acid (FA) composition as a sensitive biomarker in littoral crabs.

Investigating seasonal metal impact on Stramonita haemastoma gastropod along the Algerian East Coast: Understanding through various pollution indicators

The main objective of this study was to assess the impact of environmental pollution on the gastropod Stramonita haemastoma by examining various physiological and biochemical parameters. Trace metal elements (TME) were measured in the snail's foot. Over a one-year period from 2013 to 2014, the study investigated the variations in reduced glutathione, malondialdehyde, metallothionein, glutathione S-transferase, acetylcholinesterase and catalase activities in the foot of the gastropod at three different sites. The results showed spatiotemporal fluctuations in biomarkers, physiological parameters and TME. This integrative approach, being the first of its kind in the region using S. haemastoma as a model organism, represents a means of environmental assessment accessible to all countries allowing the monitoring and conservation of coastal marine environments on a national and international scale and which could be used in marine biomonitoring programs to indicate the impact of pollution and assess the quality of the Algerian coastal marine environment.

Molecular changes in oysters Crassostrea gigas (Thunberg, 1793) from aquaculture areas of Santa Catarina Island bays (Florianópolis, Brazil) reveal anthropogenic effects

Anthropogenic activities in coastal regions cause risks to the environmental and human health. Due to the carcinogenic and mutagenic potential, polycyclic aromatic hydrocarbons (PAH) are considered priority for monitoring. Most of the Brazilian production of Crassostrea gigas oysters are placed in the Bays of Santa Catarina Island. The aim of this study was to evaluate molecular responses (phase I and II of biotransformation and antioxidant defense) of C. gigas from six oyster farming areas potentially contaminated by sanitary sewage in Florianópolis Metropolitan (SC, Brazil): Santo Antônio de Lisboa, Sambaqui, Serraria, Caieira, Tapera, Imaruim. We evaluated the transcript levels of CYP1A1-like, CYP2-like, CYP2AU2-like, CYP356A1, GSTA1A-like, GSTO.4A-like, SULT-like, SOD-like and CAT-like by qRT-PCR. Only oysters from Caieira showed levels of thermotolerant coliforms allowed by the law. Chemicals analyses in soft tissues of oysters showed low to average levels of PAH in all monitored areas. Enhanced transcript levels of phase I (CYP1A1-like, CYP3564A1-like, CYP2-like and CYP2AU2-like) were observed in oysters from Serraria and Imaruí, suggesting higher biotransformation activity in these farming areas. Regarding phase II of biotransformation, GSTO.4A-like was up-regulated in oysters from Imaruí compared to Caieira and Santo Antônio de Lisboa. An upregulation of SOD-like and CAT-like were observed in oysters from Imaruí and Serraria, suggesting that oysters from these sites are facing higher prooxidant conditions compared to other areas. By integrating the biological and chemical data it is suggested that human-derived contaminants are affecting the oyster metabolism in some farming areas.

Integrated transcriptomics and metabolomics analyses reveal benzo[a]pyrene enhances the toxicity of mercury to the Manila clam, Ruditapes philippinarum

Mercury (Hg²⁺) and benzo[a]pyrene (BaP) are ubiquitous and persistent pollutants with multiple toxicities in bivalve molluscs. Here, the toxicological responses in the gills of Manila clams, Ruditapes philippinarum, to Hg²⁺ (10 μg L^-1), BaP (3 μg L^-1), and their mixture were analysed using transcriptomics and metabolomics approaches. Comparisons of the transcriptomes and metabolomes of Hg²⁺-and/or BaP-treated clams with control animals revealed the involvement of the detoxification metabolism, immune defence, energy-related pathways, and osmotic regulation in the stress response of R. philippinarum. Exposure to Hg²⁺ alone primarily enhanced the detoxification and energy metabolic pathways by significantly increasing the expression of genes associated with heat-shock proteins and oxidative phosphorylation. However, co-exposure to Hg²⁺ and BaP caused greater immunotoxicity and disrupted detoxification metabolism, the TCA cycle, glycolysis, and ATP generation. The expression levels of cytochrome P450 1A1 (CYP1A1), multidrug resistance-associated protein 1 (MRP1), and myosin (MYO), and the activity of electron transport system (ETS) in gills were detected, supporting the underlying toxic mechanisms of Hg²⁺ and BaP. We suggest that the presence of BaP enhances the toxicity of Hg²⁺ by 1) hampering the detoxification of Hg²⁺, 2) increasing the immunotoxicity of Hg²⁺, and 3) constraining energy availability for clams.

Shell form and enzymatic alterations in Lottia subrugosa (Gastropoda, Lotiidae) transplanted to a contaminated site

Studies have shown that shell morphology and enzymatic activities in mollusks are affected by contaminants exposure. However, the correlation between enzymatic activities and the biomineralization process are not fully understood. The present study used a transplant bioassay and field sampling to evaluate shell measurements and the activities of carbonic anhydrase, Ca²⁺-ATPase, and Mg²⁺-ATPase in Lottia subrugosa sampled in Brazilian sites under different contamination levels. Results showed that, in general, shells from the reference site (Palmas) were more rounded than the ones from the contaminated site (Balsa). Effects in enzymatic activities in specimens from transplant bioassay were attributed to the known high contaminant levels present at Balsa. While the lack of enzymatic activity alterations during field sampling was attributed to physiological adaptation to contaminants exposure. Enzymatic activities were not correlated to shell biometric parameters in field sampling, indicating that these enzymes were not related to shell alterations detected in the present study.

Mild Effects of Sunscreen Agents on a Marine Flatfish: Oxidative Stress, Energetic Profiles, Neurotoxicity and Behaviour in Response to Titanium Dioxide Nanoparticles and Oxybenzone

UV filters are potentially harmful to marine organisms. Given their worldwide dissemination and the scarcity of studies on marine fish, we evaluated the toxicity of an organic (oxybenzone) and an inorganic (titanium dioxide nanoparticles) UV filter, individually and in a binary mixture, in the turbot (Scophthalmus maximus). Fish were intraperitoneally injected and a multi-level assessment was carried out 3 and 7 days later. Oxybenzone and titanium dioxide nanoparticles induced mild effects on turbot, both isolated and in mixture. Neither oxidative stress (intestine, liver and kidney) nor neurotoxicity (brain) was found. However, liver metabolic function was altered after 7 days, suggesting the impairment of the aerobic metabolism. An increased motility rate in oxybenzone treatment was the only behavioural alteration (day 7). The intestine and liver were preferentially targeted, while kidney and brain were unaffected. Both infra- and supra-additive interactions were perceived, with a toxicodynamic nature, resulting either in favourable or unfavourable toxicological outcomes, which were markedly dependent on the organ, parameter and post-injection time. The combined exposure to the UV filters did not show a consistent increment in toxicity in comparison with the isolated exposures, which is an ecologically relevant finding providing key information towards the formulation of environmentally safe sunscreen products.

Growth and reproduction of Donax trunculus from the Gulf of Annaba (Northeast Algeria) in relation to environmental conditions

This study was aimed to evaluate the physiological reproductive end points (sex ratio, gametogenic cycle) and biological indices (condition index, length-weight relationship) in D. trunculus collected monthly over the year 2016, from two sites of the Gulf of Annaba (Northeast Algeria): El Battah (relatively unpolluted site) and Sidi Salem (polluted site). The results showed that gametogenesis takes place from December to August in both sites, with an autumnal resting phase. Also, the spawning occurred between March and August with two major spawning phases: April and August in El Battah vs May and August in Sidi Salem. The condition index showed a significant decrease in Sidi Salem site and positive correlation with gonad index. Moreover, the sites exert a significant effect on the allometric relationship and no significant effect on sex ratio. The observed reproductive events are discussed with the changes in the biological indices and the levels of pollution in the studied sites.

Preliminary Assessment of Stress and Genotoxicity Biomarkers in Bivalve Molluscs from the Gulf of Annaba, Algeria

The aim of this work is to assess biomarker responses to stresses caused by pollution of the marine environment in the Gulf of Annaba, using the bivalve mollusc Donax trunculus and Mytilus galloprovincialis. Males and females were collected during the summer from site 1 considered to be far from pollution sources (SM1 and SD1), site 2 (SM2 and SD2) exposed to a mixture of contaminants, and site 3 (SM3 and SD3) receiving the untreated sewage. The whole body was used for the determination of malonaldehyde (MDA), reduced glutathione (GSH) and DNA damage. The MDA concentration from site 2 of both species has indicated significant augmentation. The two bivalves from S2 and S3 have recorded significant decrease of GSH level, with the highest number of Comet scores. A significant site and sex effect was measured for the level of GSH and MDA, accompanied with a significant site effect for DNA damage. The genotoxicity seems correlated with the stress biomarkers and dependent on the effluent types.