Toxic Effects of Cadmium on Fish

Response and adaptation mechanisms of Apostichopus japonicus to single and combined anthropogenic stresses of polystyrene microplastics or cadmium

Microplastics (MPs) have become pervasive in marine ecosystems, exerting detrimental effects on marine life. The concurrent presence and interaction of MPs and heavy metals in aquatic environments could engender more insidious toxicological impacts. This study aimed to elucidate the potential impacts and underlying mechanisms of polystyrene microplastics (PS-MPs), cadmium (Cd), and their combined stress (MPs-Cd) on sea cucumbers (Apostichopus japonicus). It focused on the growth, Cd bioaccumulation, oxidative stress responses, immunoenzymatic activities, and metabolic profiles, specifically considering PS-MPs sizes preferentially ingested by these organisms. The high-dose MPs (MH) treatment group exhibited an increase in cadmium bioavailability within the sea cucumbers. Exposure to PS-MPs or Cd triggered the activation of antioxidant defenses and immune responses. PS-MPs and Cd exhibited a synergistic effect on lysozyme (LZM) activity. A total of 149, 316, 211, 197, 215, 619, 434, and 602 differentially expressed metabolites were identified, distinguishing the low-dose MPs (ML), high-dose MPs (MH), low-dose Cd (LCd), low-dose MPs and low-dose Cd (MLLCd), high-dose MPs and low-dose Cd (MHLCd), high-dose Cd (HCd), low-dose MPs and high-dose Cd (MLHCd), high-dose MPs and high-dose Cd (MHHCd) groups, respectively. Metabolomic analyses revealed disruptions in lipid metabolism, nervous system function, signal transduction, and transport and catabolism pathways following exposure to PS-MPs, Cd, and MPs-Cd. Correlation analyses among key differentially expressed metabolites (DEMs) underscored the interregulation among these metabolic pathways. These results offer new perspectives on the distinct and synergistic toxicological impacts of microplastics and cadmium on aquatic species, highlighting the complex interplay between environmental contaminants and their effects on marine life.

Understanding the links between micro/nanoplastics-induced gut microbes dysbiosis and potential diseases in fish: A review

At present, the quantity of micro/nano plastics in the environment is steadily rising, and their pollution has emerged as a global environmental issue. The tendency of their bioaccumulation in aquatic organisms (especially fish) has intensified people's attention to their persistent ecotoxicology. This review critically studies the accumulation of fish in the intestines of fish through active or passive intake of micro/nano plastics, resulting in their accumulation in intestinal organs and subsequent disturbance of intestinal microflora. The key lies in the complex toxic effect on the host after the disturbance of fish intestinal microflora. In addition, this review pointed out the characteristics of micro/nano plastics and the effects of their combined toxicity with adsorbed pollutants on fish intestinal microorganisms, in order to fully understand the characteristics of micro/nano plastics and emphasize the complex interaction between MNPs and other pollutants. We have an in-depth understanding of MNPs-induced intestinal flora disorders and intestinal dysfunction, affecting the host's systemic system, including immune system, nervous system, and reproductive system. The review also underscores the imperative for future research to investigate the toxic effects of prolonged exposure to MNPs, which are crucial for evaluating the ecological risks posed by MNPs and devising strategies to safeguard aquatic organisms.

Impact of cadmium and diclofenac exposure on biochemical responses, transcriptome, gut microflora, and growth performance in grass carp (Ctenopharyngodonidella)

In recent years, the concentrations of cadmium (Cd) and diclofenac (DCF) in water have frequently exceeded the standard; however, the toxic effects of these two pollutants on grass carp under single and combined exposure are unknown. In this study, the concentrations of pollutants in different tissues were detected, and the toxicities of the two pollutants to grass carp under different exposure conditions were compared based on growth traits, biochemical responses, gut microbiome, and transcriptomes. Based on these findings, the brain showed the lowest levels of Cd and DCF accumulation. Oxidative stress and pathological damage were observed in the brain and intestines. Changes in the structure and abundance of the gut microflora affect the synthesis of neurotransmitters, such as GABA and steroids. Differentially expressed genes in the brain were enriched in circadian rhythm functions. The expression of PER, CLOCK,1L-1β, 1L-17, and other genes are related to the abundance of Akkermansia, which indicates that the disorder of gut microflora will affect the normal circadian rhythm of the brain. All indices in the recovery group showed an increasing trend. Overall, the toxicity of Cd and DCF showed antagonism, and a single exposure had a stronger effect on gut microorganisms and circadian rhythm, which provided a scientific basis for exploring the comprehensive effects of different pollutants.

Chronic Cadmium Exposure can Alter Energy Allocation to Physiological Functions in the Shrimp Penaeus vannamei

Environmental stressors in aquatic organisms can be assessed using a bioenergetic approach based on the evaluation of changes in their physiological parameters. We evaluated the chronic effects of cadmium (Cd2+) on the energy balance as well as the survival, growth, metabolism, nitrogen excretion, hepatosomatic index, oxidized energy substrate, and osmoregulation of the shrimp Penaeus vannamei with the hypothesis that the high energy demand related to the homeostatic regulation of Cd2+could disrupt the energy balance and as a consequence, their physiological functions. The shrimp exposed to Cd2+ had higher mortality (30%), directed more energy into growth (33% of energy intake), ingested 10% more energy, and defecated less than control animals. Cd2+ exposure caused a tendency to decrease metabolism and ammonia excretion but did not alter the hepatosomatic index, type of energy substrate oxidized, and the hyperosmorregulatory pattern of the species. The Cd+2 exposure may have induced a trade-off response because there was a growth rate increase accompanied by increased mortality.

Interactions of binary mixtures of metals on rainbow trout (Oncorhynchus mykiss) heart mitochondrial H2O2 homeodynamics

For continuous pumping of blood, the heart needs a constant supply of energy (ATP) that is primarily met via oxidative phosphorylation in the mitochondria of cardiomyocytes. However, sustained high rates of electron transport for energy conversion redox reactions predisposes the heart to the production of reactive oxygen species (ROS) and oxidative stress. Mitochondrial ROS are fundamental drivers of responses to environmental stressors including metals but knowledge of how combinations of metals alter mitochondrial ROS homeodynamics remains sparse. We explored the effects and interactions of binary mixtures of copper (Cu), cadmium (Cd), and zinc (Zn), metals that are common contaminants of aquatic systems, on ROS (hydrogen peroxide, H2O2) homeodynamics in rainbow trout (Oncorhynchus mykiss) heart mitochondria. Isolated mitochondria were energized with glutamate-malate or succinate and exposed to a range of concentrations of the metals singly and in equimolar binary concentrations. Speciation analysis revealed that Cu was highly complexed by glutamate or Tris resulting in Cu2+ concentrations in the picomolar to nanomolar range. The concentration of Cd2+ was 7.2-7.5 % of the total while Zn2+ was 15 % and 21 % of the total during glutamate-malate and succinate oxidation, respectively. The concentration-effect relationships for Cu and Cd on mitochondrial H2O2 emission depended on the substrate while those for Zn were similar during glutamate-malate and succinate oxidation. Cu + Zn and Cu + Cd mixtures exhibited antagonistic interactions wherein Cu reduced the effects of both Cd and Zn, suggesting that Cu can mitigate oxidative distress caused by Cd or Zn. Binary combinations of the metals acted additively to reduce the rate constant and increase the half-life of H2O2 consumption while concomitantly suppressing thioredoxin reductase and stimulating glutathione peroxidase activities. Collectively, our study indicates that binary mixtures of Cu, Zn, and Cd act additively or antagonistically to modulate H2O2 homeodynamics in heart mitochondria.

Evaluation of Aflatoxins and Heavy Metals Exposure in the Local Feeds of Fish and Shrimp in Bangladesh

This study aims to comprehensively assess the presence of aflatoxins, pervasive fungal toxins, and heavy metals (lead, chromium, cadmium) in the local feed of fish and shrimp. Forty-eight samples of the fish and shrimp feed were collected from the Dhaka and Sathkhira districts of Bangladesh respectively. Aflatoxins (B1, B2, G1, G2) were analyzed by high-performance liquid chromatography (HPLC) with fluorescence detector, and atomic absorption spectrophotometry (AAS) was used for the heavy metal detection after sample digestion. The standard analytical methods of the Association of Official Analytical Chemists were followed for analyzing the proximate composition of the feed samples. The findings revealed the high toxic concentration of total aflatoxins particularly in fish feed (196.25 μg/kg). Concurrently, varying concentrations of heavy metals, including lead (Pb) and chromium (Cr), were detected, with the highest levels found in shrimp feed at 3.324 and 174.6 mg/kg, respectively. In comparison, highest contamination of cadmium (Cd) was found in fish feed at 0.398 mg/kg. The outcomes are growing concerns regarding the quality of locally sourced feed and emphasizing the need for prompt corrective actions. Otherwise, neglecting this concern may lead to the possibility of both fish and, ultimately, humans who consume them being vulnerable to the absorption and accumulation of these assessed toxic compounds.

Evaluation of Alternative Sources of Proteins and Other Nutrients with Potential Applications in Fish Nutrition

The European Union's (EU) agricultural self-sufficiency is challenged by its reliance on imported plant proteins, particularly soy from the Americas, contributing to deforestation and greenhouse gas emissions. Addressing the EU's protein deficit, this study evaluates alternative protein sources for aquaculture, focusing on their nutritional value, elemental content, and polycyclic aromatic hydrocarbons (PAHs). Protein flours from gastropods (Helix pomatia, Arion lusitanicus, Arion vulgaris) and their hepatopancreas, along with plant-based proteins from food industry by-products (oilcakes, coffee grounds, spent brewer's yeast), were analyzed. Results revealed that snail flour contained the highest protein content at 59.09%, significantly outperforming hepatopancreas flour at 42.26%. Plant-based proteins demonstrated substantial nutritional value, with coffee grounds flour exhibiting a remarkable protein content of 71.8% and spent brewer's yeast flour at 57.9%. Elemental analysis indicated high levels of essential minerals such as magnesium in hepatopancreas flour (5719.10 mg/kg) and calcium in slug flour (48,640.11 mg/kg). However, cadmium levels in hepatopancreas flour (11.45 mg/kg) necessitate caution due to potential health risks. PAH concentrations were low across all samples, with the highest total PAH content observed in hepatopancreas flour at 0.0353 µg/kg, suggesting minimal risk of PAH-related toxicity. The analysis of plant-based protein sources, particularly oilcakes derived from sunflower, hemp, flax, and pumpkin seeds, revealed that these by-products not only exhibit high protein contents but present a promising avenue for enhancing the nutritional quality of feed. This study underscores the potential of utilizing gastropod and plant-based by-products as sustainable and nutritionally adequate alternatives to conventional feeds in aquaculture, contributing to the EU's environmental sustainability goals.

An integrative data-centric approach to derivation and characterization of an adverse outcome pathway network for cadmium-induced toxicity

Cadmium is a prominent toxic heavy metal that contaminates both terrestrial and aquatic environments. Owing to its high biological half-life and low excretion rates, cadmium causes a variety of adverse biological outcomes. Adverse outcome pathway (AOP) networks were envisioned to systematically capture toxicological information to enable risk assessment and chemical regulation. Here, we leveraged AOP-Wiki and integrated heterogeneous data from four other exposome-relevant resources to build the first AOP network relevant for inorganic cadmium-induced toxicity. From AOP-Wiki, we filtered 309 high confidence AOPs, identified 312 key events (KEs) associated with inorganic cadmium from five exposome-relevant databases using a data-centric approach, and thereafter, curated 30 cadmium relevant AOPs (cadmium-AOPs). By constructing the undirected AOP network, we identified a large connected component of 18 cadmium-AOPs. Further, we analyzed the directed network of 59 KEs and 82 key event relationships (KERs) in the largest component using graph-theoretic approaches. Subsequently, we mined published literature using artificial intelligence-based tools to provide auxiliary evidence of cadmium association for all KEs in the largest component. Finally, we performed case studies to verify the rationality of cadmium-induced toxicity in humans and aquatic species. Overall, cadmium-AOP network constructed in this study will aid ongoing research in systems toxicology and chemical exposome.

Foraging Activity of Honey Bees (Apis mellifera L., 1758) and Exposure to Cadmium: a Review

Honey bees are commonly exposed to a broad spectrum of xenobiotics, including heavy metals. Heavy metal toxicity is of concern in the context of global pollinator declines, especially since honey bees seem to be particularly susceptible to xenobiotics in general. Here we summarize current knowledge on the interplay between cadmium, one of the most toxic and mobile elements in the environment, and honey bees, the primary managed pollinator species worldwide. Overall, cadmium pollution has been shown to be ubiquitous, affecting industrial, urban and rural areas alike. Uptake of this heavy metal by plants serves as the primary route of exposure for bees (through pollen and nectar). Reported cadmium toxicity consists of lethal and sublethal effects (reduced development and growth) in both adult and larval stages, as well as various molecular responses related to detoxification and cellular antioxidant defence systems. Other effects of cadmium in honey bees include the disruption of synaptic signalling, calcium metabolism and muscle function.

Unveiling the silent threat: Heavy metal toxicity devastating impact on aquatic organisms and DNA damage

Heavy metal pollution has significant impacts on aquatic fauna and flora. It accumulates in marine organisms, both plants and animals, which are then consumed by humans. This can lead to various health problems, such as organ damage and the development of cancer. Additionally, this pollution causes biological magnification, where the toxicity concentration gradually increases as aquatic organisms continuously accumulate metals. This process results in apoptotic mechanisms, antioxidant defence, and inflammation, which are reflected at the gene expression level. However, there is limited research on specific heavy metals and their effects on fish organs. The concentration of metal contamination and accumulation in different tropical environments is a concern due to their toxicity to living organisms. Therefore, this review focuses on determining the influences of metals on fish and their effects on specific organs, including DNA alterations.

Hepatocellular degeneration in mice co-exposed to in-utero aluminium and cadmium: Implication of a disordered antioxidant and energy homeostatic response in the liver

The current study comprised four groups of pregnant animals viz; Control (CTR) received 10 ml/kg of normal saline, Al:10 mg/kg of AlCl3, Cd: 1.5 mg/Kg of CdCl2 Al+Cd; 10 mg/kg of AlCl3 and 1.5 mg/Kg of CdCl2. Treatment was done from pregnancy days (PNT) 7-20. After delivery, male animals were weaned on PSD 21 and sacrificed on PSD 78. From the study significant increases on serum liver enzymes in the group exposed to Cd and that exposed to Al+Cd were observed. The study further showed altered serum and hepatic antioxidant balance for the Cd, Al and Al+Cd groups compared to control. Similarly, lactate dehydrogenase (LDH) and succinate dehydrogenase (SDH) activities in the liver were elevated in Cd and Al+Cd groups while an altered liver histological feature in treated groups were also observed. it was concluded that in utero co-exposure to Al and Cd had the ability to alter hepatic functional indices.

Unveiling the underwater threat: Exploring cadmium's adverse effects on tilapia

Prolonged exposure to environmentally relevant amounts of cadmium (Cd) in aquatic environments, even at small doses (0.1 and 1 μg/L), might endanger the health of underwater creatures. This research delved into the impacts of a four-month cadmium exposure on Mozambique tilapia (Oreochromis mossambicus), aiming to uncover the mechanisms behind it. Through close examination, we found that the 4-momth cadmium exposure led to harmful effects on the fish's gills, muscles, brain, and intestines. This exposure also triggered changes in gene expressions in the brain and liver, affected the respiratory system and weakened liver's ability to detoxify and defend against potential infections. Looking deeper into the fish's gut, we noticed alterations in energy-related genes and disruptions in immune pathways, making it more susceptible to illnesses. The exposure to cadmium also had an impact on the fish's gut and water-dwelling microorganisms, reducing diversity and encouraging harmful microbial communities. Interestingly, some gut microbes seemed to assist in breaking down and detoxifying cadmium, which could potentially protect the fish. Taken together, prolonged low-level cadmium exposure impaired gill, muscle, and brain function, suppressed immunity, disrupted intestines, and altered microbial balance, leading to hindered growth. These insights illuminate cadmium's impact on fish, addressing vital environmental concerns.

Lead and cadmium in blood and tissues of Atlantic bluefin tuna (Thunnus thynnus L., 1758)

Cadmium (Cd) and lead (Pb) levels in blood and tissues of Atlantic bluefin tuna were analysed to gather information regarding their distribution, accumulation and inter-relationships, as well as to examine how sex affects them. In the whole population, the concentration range was from below the detection limit (bone) to 8.512 μg g-1 (liver) for Cd, and from below detection limit (bone and gills) to 0.063 μg g-1 (kidney) for Pb. The median concentration in the muscles (0.008 and 0.029 μg g-1 for Cd and Pb, respectively) was 10 times less than the maximum permitted for consumption. Sex was shown to be an important variable affecting concentrations of Cd in both liver and kidneys, so taking into account sex when interpreting results is highly recommended. The importance of Cd and Pb bioaccumulation in fishery by-products, increasingly important in commercial circuits, is also highlighted.

Understanding the mechanistic roles of microplastics combined with heavy metals in regulating ferroptosis: Adding new paradigms regarding the links with diseases

As a new type of pollutant, microplastics (MPs) commonly exist in today's ecosystems, causing damage to the ecological environment and the health of biological organisms, including human beings. MPs can function as carriers of heavy metals (HMs) to aggravate the enrichment of HMs in important organs of organisms, posing a great threat to health. Ferroptosis, a novel process for the regulation of nonapoptotic cell death, has been shown to be closely related to the occurrence and processes of MPs and HMs in diseases. In recent years, some HMs, such as cadmium (Cd), iron (Fe), arsenic (As) and copper (Cu), have been proven to induce ferroptosis. MPs can function as carriers of HMs to aggravate damage to the body. This damage involves oxidative stress, mitochondrial dysfunction, lipid peroxidation (LPO), inflammation, endoplasmic reticulum stress (ERS) and so on. Therefore, ferroptosis has great potential as a therapeutic target for diseases induced by MPs combined with HMs. This paper systematically reviews the potential effects and regulatory mechanisms of MPs and HMs in the process of ferroptosis, focusing on the mitochondrial damage, Fe accumulation, LPO, ERS and inflammation caused by MPs and HMs that affect the regulatory mechanism of ferroptosis, providing new insights for research on regulating drugs and for the development of ferroptosis-targeting therapy for Alzheimer's disease, Parkinson's disease, cancer and cardiovascular disease.

Impaired intestinal immunity and microbial diversity in common carp exposed to cadmium

Waterborne cadmium (Cd) accumulates in the fish intestine and causes irreversible toxicity by disrupting intestinal immunity and microbial diversity. To explore the toxicity of environmentally available high Cd concentration on intestinal immunity and microbial diversity of fish, we selected the widely used bioindicator model species, Common carp (Cyprinus carpio). Literature review and Cd pollution data supported sequential doses of 0.2, 0.4, 0.8, 1.6, 3.2, and 6.4 mg/L Cd for 30 days. Based on intestinal tissue Cd accumulation, previous studies, and environmentally available Cd data, 0.4 and 1.6 mg/L Cd were selected for further studies. Intestinal Cd bioaccumulation increased significantly to ~100 times in fish exposed to 1.6 mg/L Cd. We observed villous atrophy, increased goblet cells with mucus production, muscularis erosion, and thickened lamina propria due to intense inflammatory cell infiltration in the intestine at this Cd concentration. Cd-induced immunosuppression occurred with increased lysozyme, alkaline phosphate (AKP), and acid phosphate (ACP). High levels of catalase (CAT), total antioxidant capacity (T-AOC), malondialdehyde (MDA), and hydrogen peroxide (H2O2) suggested induced oxidative stress and poor metabolism by α-amylase and lipase suppression for Cd toxicity. Proteobacteria (41.2 %), Firmicutes (21.8 %), and Bacteroidetes (17.5 %) were the dominant bacterial phyla in the common carp intestine. Additionally, potential pathogenic Cyanobacteria increased in Cd-treated fish. The decrease of beneficiary bacteria like Aeromonas, and Cetobacterium indicated Cd toxicity. Overall, these findings indicate harmful consequences of high Cd concentration in the intestinal homeostasis and health status of fish.

Environment-relevant concentrations of cadmium induces necroptosis and inflammation; baicalein maintains gill homeostasis through suppressing ROS/ER stress signaling in common carps (Cyprinus carpio L.)

Cadmium (Cd) is a major contaminant in natural environments and exerts adverse effects on aquatic biota at low concentrations. Gill is as vital respiratory organ and may cause pollutants to enter fish during gas exchange. Baicalein (BAI), as a kind of flavonoids, possess antioxidant properties through inactivating free radicals. To confirm the potential effects and approaches of BAI addition in maintaining the gill stability, 90 common carps (Cyprinus carpio L.) were selected and randomly divided into water environment exposure group (0.22 mg/L Cd) and/or feed added with 0.10 g/kg BAI for 30 days. The analysis of ion content in serum showed that Cd exposure disturbed ion homeostasis, and BAI could reduce serum Cd concentration. The histopathological results of gills showed that Cd exposure caused gill tissue lesions and structural damage, and BAI feeding effectively alleviated this damage. In addition, BAI could enhance antioxidant activity and activate Nrf2/HO-1 axis, thereby reducing oxidative stress and endoplasmic reticulum (ER) stress. Moreover, BAI lightened cytokine imbalance, inflammatory response, and necroptosis. Overall, the results indicated that BAI feeding could maintain gill homeostasis against Cd poisoning via the ROS/ER stress signaling. This trial revealed the properties of BAI resistance to metal Cd in aquaculture and partially elucidated its mechanism.

The Role of Glutathione and Sulfhydryl Groups in Cadmium Uptake by Cultures of the Rainbow Trout RTG-2 Cell Line

The aim of this study is to investigate the role of cellular sulfhydryl and glutathione (GSH) status in cellular cadmium (Cd) accumulation using cultures of the rainbow trout cell line RTG-2. In a first set of experiments, the time course of Cd accumulation in RTG-2 cells exposed to a non-cytotoxic CdCl2 concentration (25 μM) was determined, as were the associated changes in the cellular sulfhydryl status. The cellular levels of total GSH, oxidized glutathione (GSSG), and cysteine were determined with fluorometric high-performance liquid chromatography (HPLC), and the intracellular Cd concentrations were determined with inductively coupled plasma mass spectrometry (ICP-MS). The Cd uptake during the first 24 h of exposure was linear before it approached a plateau at 48 h. The metal accumulation did not cause an alteration in cellular GSH, GSSG, or cysteine levels. In a second set of experiments, we examined whether the cellular sulfhydryl status modulates Cd accumulation. To this end, the following approaches were used: (a) untreated RTG-2 cells as controls, and (b) RTG-2 cells that were either depleted of GSH through pre-exposure to 1 mM L-buthionine-SR-sulfoximine (BSO), an inhibitor of glutathione synthesis, or the cellular sulfhydryl groups were blocked through treatment with 2.5 μM N-ethylmaleimide (NEM). Compared to the control cells, the cells depleted of intracellular GSH showed a 25% reduction in Cd accumulation. Likewise, the Cd accumulation was reduced by 25% in the RTG-2 cells with blocked sulfhydryl groups. However, the 25% decrease in cellular Cd accumulation in the sulfhydryl-manipulated cells was statistically not significantly different from the Cd accumulation in the control cells. The findings of this study suggest that the intracellular sulfhydryl and GSH status, in contrast to their importance for Cd toxicodynamics, is of limited importance for the toxicokinetics of Cd in fish cells.

Ecotoxicology applied to conservation: Potential negative metal and metalloid contamination effects on the homeostatic balance of the critically endangered Brazilian guitarfish, Pseudobatos horkelii (Elasmobranchii: Rhinobatidae)

Metal contamination poses a significant threat to elasmobranchs, underscoring the need for targeted conservation approaches. The critically endangered Brazilian guitarfish, Pseudobatos horkelii, confronts an array of challenges, notably overexploitation, putting its survival at risk. Our study investigated the potential toxicity arising from arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb) contamination across various adult guitarfish tissues from southeastern Brazil. Serological stress indicators, nutritional metabolites, and creatinine, an organ function marker, were also assessed, and Selenium (Se) levels were also investigated for possible protective effects. Our investigation unveiled significant correlations between metal concentrations and the determined physiological markers, shedding light on potential adverse effects. Remarkably, six correlations were indicative of how Hg and Pb negatively impact hepatic metabolite assimilation, while As was shown to influence renal phosphorus dynamics, Cd to affect rectal gland phosphorus regulation, and Pb to influence creatinine production in muscle tissue. Furthermore, Se demonstrated protective properties against Cd, Hg, and Pb, suggesting a role in alleviating the toxicity of these elements. Despite probable protective Se influences, the detected elemental interactions still suggest potential for organ impairment. These findings gain heightened significance within the context of the cumulative stressors faced by the Brazilian guitarfish, with metal contamination exhibiting the capacity to erode this species resilience against both anthropogenic and environmental pressures, thereby disrupting systemic equilibrium and jeopardizing wild populations. By investigating the intricate balance between metal accumulation and physiological consequences, our study contributes with crucial insights into potential conservation strategy formulations towards pollution for this critically endangered elasmobranch species.

Review of cadmium toxicity effects on fish: Oxidative stress and immune responses

Cadmium (Cd) in aquatic environments can cause environmental toxicity to fish and induce oxidative stress owing to an excessive production of reactive oxygen species in fish bodies. Fish have developed various antioxidant systems to protect themselves from reactive oxygen species; thus, a change in antioxidant responses in fish can be a criterion for evaluating oxidative stress resulting from Cd exposure. Because Cd exposure may be recognized as an exogenous substance by a fish body, it may lead to the stimulation or suppression of its immune system. Various immune responses can be assessed to evaluate Cd toxicity in fish. This review aimed to identify the impacts of Cd exposure on oxidative stress and immunotoxicity in fish as well as identify accurate indicators of Cd toxicity in aquatic ecosystems.

Cadmium-109 Internal Kinetics in Diamond Sturgeon Acipenser gueldenstaedtii are Strongly Influenced by Salinity, Exposure Pathway and History

Cadmium-109 whole-body and internal biokinetics were experimentally investigated in critically endangered diamond sturgeon Acipenser gueldenstaedtii after uptake from water or food, in fresh (FW) and brackish (BW; 9‰) salinities typical of the Caspian Sea. Whole-body rates of uptake of 109Cd from water and subsequent depuration were quantified over 14 and 28 days, respectively. Uptake was greater in FW than BW by a factor of 2.4, but depuration rates were similar in both salinities. In contrast, for the dietary (chironomid) exposure pathway 109Cd assimilation efficiencies (AEs) were higher in BW (13%) compared to FW (9.5%). Head (including gills) or digestive tract were major repositories of 109Cd following aqueous and dietary exposures, respectively, including both uptake and depuration phases. The point-of-entry of 109Cd into the body was also a major and persistent determiner of its subsequent internal distribution. For aqueous exposures, the internal distributions of 109Cd changed appreciably during depuration with increased activity concentrations in some body components, which again varied with salinity. Increased salinity appreciably enhanced the percentage distributions and activity concentrations of 109Cd in the liver, kidney and digestive tract, which are typically most pathologically altered by elevated Cd exposure. For dietary exposure, increased salinity also enhanced 109Cd activity concentrations in most body components. The results repeatedly indicate the important role of salinity in the whole-body and internal biokinetics of 109Cd in A. gueldenstaedtii, a representative of both a phylogenetically distinct and most endangered family of fishes.

Does Dietary Sodium Alginate with Low Molecular Weight Affect Growth, Antioxidant System, and Haemolymph Parameters and Alleviate Cadmium Stress in Whiteleg Shrimp (Litopenaeus vannamei)?

Decreasing low molecular weight can improve the digestibility and availability of ingredients such as sodium alginate. This study aimed to test the four dosages of low molecular weight sodium alginate (LMWSA) (0%: Control, 0.05%: 0.5 LMWSA, 0.10%: 1.0 LMWSA, and 0.2%: 2.0 LMWSA) in whiteleg shrimp (Litopenaeus vannamei) (3.88 ± 0.25 g) for eight weeks. After finishing the trial, shrimp were exposed to cadmium (1 mg/L) for 48 h. While feed conversion ratio (FCR) improved in shrimp fed dietary 2.0 LMWSA (p < 0.05), there was no significant difference in growth among treatments. The results showed a linear relation between LMWSA level and FCR, and glutathione S-transferase (GST) before; and malondialdehyde (MDA), glutathione (GSH), GST, and alanine transaminase (ALT) after cadmium stress (p < 0.05). The GST, MDA, ALT, and aspartate transaminase (AST) contents were changed after stress but not the 2.0 LMWSA group. The survival rate after stress in 1.0 LMWSA (85.23%) and 2.0 LMWSA (80.20%) treatments was significantly higher than the Control (62.05%). The survival rate after stress negatively correlated with GST and ALT, introducing them as potential biomarkers for cadmium exposure in whiteleg shrimp. Accordingly, the 2.0 LMWSA treatment had the best performance in the abovementioned parameters. As the linear relation was observed, supplementing more levels of LMWSA to reach a plateau is recommended.

Factors Affecting the Adsorption of Heavy Metals by Microplastics and Their Toxic Effects on Fish

Fish not only constitute an important trophic level in aquatic ecosystems but also serve as an important source of protein for human beings. The health of fish is related to the sustained and healthy development of their entire aquatic ecosystem. Due to the widespread use, mass production, high disposal frequency, and degradation resistance of plastics, these pollutants are released into aquatic environments on a large scale. They have become one of the fastest growing pollutants and have a substantial toxic effect on fish. Microplastics have intrinsic toxicity and can absorb heavy metals discharged into water. The adsorption of heavy metals onto microplastics in aquatic environments is affected by many factors and serves as a convenient way for heavy metals to migrate from the environment to organisms. Fish are exposed to both microplastics and heavy metals. In this paper, the toxic effects of heavy metal adsorption by microplastics on fish are reviewed, and the focus is on the toxic effects at the individual (survival, feeding activity and swimming, energy reserves and respiration, intestinal microorganisms, development and growth, and reproduction), cellular (cytotoxicity, oxidative damage, inflammatory response, neurotoxicity, and metabolism) and molecular (gene expression) levels. This facilitates an assessment of the pollutants' impact on ecotoxicity and contributes to the regulation of these pollutants in the environment.

After a Century of Research into Environmental Mutagens and Carcinogens, Where Do We Stand?

Cancer is one of the longest-known human diseases, yet only in recent times have we begun to perceive that the percentage of neoplasms caused by environmental factors, lifestyle and chemicals, is likely underestimated. The first medical reports associating cancer with pollutants like tars appeared by the early 20th century, but despite initial evidence relating oncogenesis and chromosomal alterations, only after the structure of DNA had been elucidated in the 1950s have genetic disorders been fully perceived as cause. This led to a growing interest in genotoxic and mutagenic pollutants. Even though we are now familiar with a range of environmental carcinogens spanning between aromatic hydrocarbons and asbestos to radionuclides and forms of carbon nanomaterials, establishing causal networks between pollutants and cancer remains cumbersome. In most part, this is due to the complexity of toxicant matrices, unknown modes-of-action of chemicals or their mixtures, the widening array of novel pollutants plus difficulties in subtracting background effects from true aetiology of disease. Recent advances in analytical chemistry, high-throughput toxicology, next-generation sequencing, computational biology and databases that allocate whole normal and cancer genomes, all indicate that we are on the verge of a new age of research into mechanistic 'oncotoxicology', but how can it impact risk assessment and prevention?