Oxidative damage, ultrastructural alterations and gene expressions of hemocytes in the freshwater crab Sinopotamon henanense exposed to cadmium

Assessing Metal Toxicity on Crustaceans in Aquatic Ecosystems: A Comprehensive Review

Residual concentrations of some trace elements and lightweight metals, including cadmium, copper, lead, mercury, silver, zinc, nickel, chromium, arsenic, gallium, indium, gold, cobalt, polonium, and thallium, are widely detected in aquatic ecosystems globally. Although their origin may be natural, human activities significantly elevate their environmental concentrations. Metals, renowned pollutants, threaten various organisms, particularly crustaceans. Due to their feeding habits and habitat, crustaceans are highly exposed to contaminants and are considered a crucial link in xenobiotic transfer through the food chain. Moreover, crustaceans absorb metals via their gills, crucial pathways for metal uptake in water. This review summarises the adverse effects of well-studied metals (Cd, Cu, Pb, Hg, Zn, Ni, Cr, As, Co) and synthesizes knowledge on the toxicity of less-studied metals (Ag, Ga, In, Au, Pl, Tl), their presence in waters, and impact on crustaceans. Bibliometric analysis underscores the significance of this topic. In general, the toxic effects of the examined metals can decrease survival rates by inducing oxidative stress, disrupting biochemical balance, causing histological damage, interfering with endocrine gland function, and inducing cytotoxicity. Metal exposure can also result in genotoxicity, reduced reproduction, and mortality. Despite current toxicity knowledge, there remains a research gap in this field, particularly concerning the toxicity of rare earth metals, presenting a potential future challenge.

Saccharomyces cerevisiae supplemented diets mitigate the effects of waterborne cadmium toxicity on gilthead seabream (Sparus aurata L.): growth performance, haemato-biochemical, stress biomarkers, and histopathological investigations

Yeast, Saccharomyces cerevisiae, has been utilized as a probiotic in aqua-feeds to promote growth and alleviate the stress in aquatic animals. On the other hand, cadmium (Cd) toxicity causes serious retardation of growth and welfare status of aquatic animals. The present study was conducted to evaluate the protective role of dietary yeast in mitigating the waterborne Cd toxicity effects on the growth, haemato-biochemical, stress biomarkers, and histopathological investigations of gilthead seabream (Sparus aurata L.). In a 3 × 3 factorial design, the acclimated fish (20-24 g) were randomly distributed into nine treatments in triplicates where they were fed on 0.0% (control), 0.5%, and 1.0% of yeast along with exposure to 0.0, 1.0, and 2.0 mg Cd/L for 60 days. All growth parameters and mRNA expressions of IGF-1 and GH genes as well as haematological parameters were markedly increased with the increase of dietary yeast levels; meanwhile these variables were significantly retarded with Cd exposure. Contradictory effects on the above-mentioned variables were observed with Cd toxicity. In contrast, blood cortisol, glucose, total cholesterol, and triglyceride, lactate dehydrogenase, alanine transaminase, aspartate transaminase, alkaline phosphatase, in addition to DNA fragments % were noticeably increased with Cd toxicity especially at the treatment of 2.0 mg Cd/L, while decreasing with increasing dietary yeast levels. Compared with the control fish group, Cd concentrations in the gill, liver, and muscle tissues of gilthead seabream were higher in Cd-exposed treatments, especially at the treatment of 2.0 mg Cd/L. Deposition of Cd in fish liver was higher than that in gill tissues but lowest Cd residue was observed in muscle tissues. No significant changes in Cd residues in fish organs were observed in yeast-fed fish with no Cd exposure. The Cd exposure negatively affected histological status of gill, liver, and kidney tissues of S. aurata; while feeding Cd-exposed fish on yeast diets lowered the Cd residues in fish organs and recovered the adverse effects of Cd toxicity. Hence, this study recommends the addition of bakery yeast (1.0%) to fish diets to improve the performance, overall welfare, and histopathological status of gilthead seabream, S. aurata.

Saccharomyces cerevisiae additions normalized hemocyte differential genes expression and regulated crayfish (Procambarus clarkii) oxidative damage under cadmium stress

Because China produces the most crayfish in the world, safe solutions must be improved to mitigate the risks of ongoing heavy metal stressors accumulation. This study aimed to use Saccharomyces cerevisiae as a bioremediation agent to counteract the harmful effect of cadmium (Cd) on crayfish (Procambarus clarkia). Our study used three concentrations of S. cerevisiae on crayfish feed to assess their Cd toxicity remediation effect by measuring total antioxidant capacity (TAC) and the biomarkers related to oxidative stress like malondialdehyde (MDA), protein carbonyl derivates (PCO), and DNA-protein crosslink (DPC). A graphite furnace atomic absorption spectroscopy device was used to determine Cd contents in crayfish. Furthermore, the mRNA expression levels of lysozyme (LSZ), metallothionein (MT), and prophenoloxidase (proPO) were evaluated before and following the addition of S. cerevisiae. The results indicated that S. cerevisae at 5% supplemented in fundamental feed exhibited the best removal effect, and Cd removal rates at days 4th, 8th, 12th, and 21st were 12, 19, 29.7, and 66.45%, respectively, which were significantly higher than the basal diet of crayfish. The addition of S. cerevisiae increased TAC levels. On the other hand, it decreased MDA, PCO, and DPC, which had risen due to Cd exposure. Furthermore, it increased the expression of proPO, which was reduced by Cd exposure, and decreased the expression of LSZ and MT, acting in the opposite direction of Cd exposure alone. These findings demonstrated that feeding S. cerevisiae effectively reduces the Cd from crayfish and could be used to develop Cd-free crayfish-based foods.

G6PDH as a key immunometabolic and redox trigger in arthropods

The enzyme glucose-6-phosphate dehydrogenase (G6PDH) plays crucial roles in glucose homeostasis and the pentose phosphate pathway (PPP), being also involved in redox metabolism. The PPP is an important metabolic pathway that produces ribose and nicotinamide adenine dinucleotide phosphate (NADPH), which are essential for several physiologic and biochemical processes, such as the synthesis of fatty acids and nucleic acids. As a rate-limiting step in PPP, G6PDH is a highly conserved enzyme and its deficiency can lead to severe consequences for the organism, in particular for cell growth. Insufficient G6PDH activity can lead to cell growth arrest, impaired embryonic development, as well as a reduction in insulin sensitivity, inflammation, diabetes, and hypertension. While research on G6PDH and PPP has historically focused on mammalian models, particularly human disorders, recent studies have shed light on the regulation of this enzyme in arthropods, where new functions were discovered. This review will discuss the role of arthropod G6PDH in regulating redox homeostasis and immunometabolism and explore potential avenues for further research on this enzyme in various metabolic adaptations.

Sources, bioaccumulation, and toxicity mechanisms of cadmium in Chlamys farreri

The Potentially toxic elements (PTEs) cadmium (Cd) is one of the most serious stressors polluting the marine environment. Marine bivalves have specific high enrichment capacity for Cd. Previous studies have investigated the tissue distribution changes and toxic effects of Cd in bivalves, but the sources of Cd enrichment, migration regulation during growth, and toxicity mechanisms in bivalves have not been fully explained. Here, we used stable-isotope labeling to investigate the contributions of Cd from different sources to scallop tissues. We sampled the entire growth cycle of Chlamys farreri, which is widely cultured in northern China, from juveniles to adult scallops. We found tissue variability in the bioconcentration-metabolism pattern of Cd in different bound states, with Cd in the aqueous accounting for a significant contribution. The accumulation pattern of Cd in all tissues during growth was more significant in the viscera and gills. Additionally, we combined a multi-omics approach to reveal a network of oxidative stress-induced toxicity mechanisms of Cd in scallops, identifying differentially expressed genes and proteins involved in metal ion binding, oxidative stress, energy metabolism, and apoptosis. Our findings have important implications for both ecotoxicology and aquaculture. They also provide new insights into marine environmental assessment and mariculture development.

Integrated physiological and transcriptome analysis reveals potential toxicity mechanism of haloxyfop-P-methyl to Chiromantes dehaani

Haloxyfop-P-methyl is widely used in controlling gramineous weeds, including the invasive plant Spartina alterniflora. However, the mechanism of its toxicity to crustaceans is unclear. In this study, we adopted transcriptome analysis combined with physiologic changes to investigate the response of estuarine crab (Chiromantes dehaani) to haloxyfop-P-methyl. The results showed that the median lethal concentration (LC₅₀) of C. dehaani to haloxyfop-P-methyl at 96 h was 12.886 mg/L. Antioxidant system analysis indicated that MDA, CAT, GR, T-GSH, and GSSG might be sensitive biomarkers that characterize the oxidative defense response of the crab. In total, 782 differentially expressed genes were identified, including 489 up-regulated and 293 down-regulated genes. Glutathione metabolism, detoxification response and energy metabolism were significantly enriched, revealing the potential toxic mechanism of haloxyfop-P-methyl to C. dehaani. These results provide a theoretical foundation for further research on haloxyfop-P-methyl toxicity to crustaceans.

Cloning, identification, and functional characterization of novel prophenoloxidases (ShproPO) from the freshwater crab Sinopotamon henanense in response to cadmium exposure and Aeromonas hydrophila infection

Prophenoloxidase (proPO) is essential in the prophenoloxidase-activating system (proPO-AS) which is important for defense against foreign infection in crustaceans. However, most studies have focused on expression in the presence of a single pathogenic bacterium, and very few have addressed the presence of environmental contaminants simultaneously, such as cadmium (Cd) and Aeromonas hydrophila. Our study aimed to investigate the function of proPO in the freshwater crab Sinopotamon henanense and the changes in its expression by Cd and infection of A. hydrophila. A novel proPO from the hemocytes of S. henanense (ShproPO) was found in this research, the full-length cDNA of ShproPO was 2620 bp of encoding a protein of 678 amino acids containing three typical hemocyanin domains. The ShproPO protein could be found in both the granular (GHc) and the semi-granular hemocytes (SGHc). The ShproPO mRNA was found to be abundantly expressed in hemocytes and could be influenced by A. hydrophila infection. These results indicate that ShproPO could be involved in the antibacterial process. Further research found that low concentrations of Cd could promote its expression after infection with A. hydrophila. Therefore, it was hypothesized that Cd disrupted the response of crabs to A. hydrophila infection. Subsequently, PO enzyme activity was found to be significantly reduced through in vivo RNA interference with ShproPO, and the results suggested that ShproPO is likely to be a key enzyme in the melanization response. Finally, ShproPO was found to significantly enhance the phagocytosis of A. hydrophila-infected hemocytes by in vitro recombination, confirming that ShproPO is involved in hemocyte-mediated melanization and phagocytosis. Our findings reveal completely new insight into the immunotoxicity of Cd and the immune function of ShproPO in S. henanense.

Behavior and toxicity assessment of copper nanoparticles in aquatic environment: A case study on red swamp crayfish

With the wide use of copper nanoparticles (CuNPs) in various industrial and commercial applications, they inevitably enter the aquatic environment. However, their behavior in the aquatic environment and potential toxicity to aquatic organisms remain little known. In this study, we investigated the behavior of CuNPs in freshwater, as well as the toxicity and bioaccumulation of CuNPs and copper sulfate (CuSO₄), used as a positive control for copper ions toxicity, in red swamp crayfish (Procambarus clarkii). The results showed that CuNPs released copper ions into freshwater and aggregated rapidly in freshwater, and their release of copper ions and aggregation slowed down at a higher concentration of CuNPs. The calculated 72-h LC₅₀ values for crayfish were 1.18 and 0.54 mg/L for CuNPs and CuSO₄, respectively. Cu accumulation in the gill and hepatopancreas from CuSO₄ treatments was significantly higher than that from CuNPs, and the highest Cu bioaccumulation level in crayfish was found in the gill, followed by hepatopancreas and muscle with the exposure of copper. The activities of the antioxidative enzymes in the crayfish significantly decreased after exposure to CuNPs for 48 h, compared to the control (without CuNPs or CuSO₄). Histological examination revealed that there was no significant alteration of hepatopancreas in the crayfish exposed to CuNPs. Meanwhile, the growth of crayfish was not significantly inhibited by CuNPs. These results suggested that CuNPs exposure can induce oxidative stress in the crayfish, gill is the main tissue for their accumulation, and their toxicity is mainly caused by the released copper ions.

Toxicological responses of juvenile Chinese shrimp Fenneropenaeus chinensis and swimming crab Portunus trituberculatus exposed to cadmium

Cadmium (Cd) is one of the typical metal pollutants in the Bohai Sea. To evaluate the acute toxicological effects of Cd on marine crustaceans, juvenile Fenneropenaeus chinensis and Portunus trituberculatus were exposed to Cd at environmentally relevant concentrations (5 and 50 μg/L) for 96 h. Cd accumulation, antioxidants and metabolite profiles were characterized to elucidate the responses of juvenile crustaceans to Cd stress. Significant Cd accumulation was observed in both juvenile crustaceans in 50 μg/L Cd-treated group. Results showed that Cd exposure induced hormesis based on the alterations of GSH, SOD and CAT activities (i.e. increased levels in the low concentration of Cd treatment and recovered levels in the high concentration of Cd treatment) in juvenile P. trituberculatus. Similarly, the responses of GSH contents presented hormesis pattern in Cd-treated juvenile F. chinensis. Na+-K+-ATPase contents were significantly elevated in 50 μg/L Cd-treated group. In addition, untargeted NMR-based metabolomics indicated Cd caused the disturbance in osmotic regulation and energy consumption in both juvenile F. chinensis and P. trituberculatus via different pathways. The immunotoxicity and movement disorder were uniquely demonstrated in juvenile P. trituberculatus after Cd exposure.

Toxicological effects of cadmium on the immune response and biomineralization of larval flounder Paralichthys olivaceus under seawater acidification

Seawater acidification can cause threats to both calcifying and uncalcifying marine organisms, affecting their acid-base regulatory functions, immune system and biomineralization. Marine pollutants, such as cadmium (Cd) that is globally distributed in coastal ecosystems, do not affect organisms alone but commonly as combined stressors. To investigate the toxicological effects of Cd on the immune and biomineralization of marine fishes under seawater acidification, flounder Paralichthys olivaceus was exposed to seawater acidification (control (pH 8.10), 7.70 and 7.30) and Cd exposure (control (0.36 μg L^-1), 0.01 and 0.15 mg L^-1 Cd) for 49 days from embryonic stage until they became settled. Immune and biomineralization-related biomarkers of flounder at the end of exposure were investigated. Results showed that single seawater acidification and Cd exposure or combined exposure significantly affected the immune system-related enzyme activities. Specifically, lysozyme (LZM) activity was significantly inhibited by single seawater acidification and Cd exposure, indicating innate immunosuppression under two stressors. Contents of IgM, HSP70 and MT were induced by seawater acidification or Cd exposure, indicating a detoxification mechanism that responded to the stressors. The expressions of immune-related genes were upregulated (hsp70 and mt) or downregulated (lzm) under Cd exposure. Of the biomineralization-related enzymes, activities of carbonic anhydrase (CA), Na⁺/K⁺-ATPase and Ca²⁺-ATPase increased under seawater acidification and Cd exposure, a potential mechanism in response to changes of acid-base balance induced by the stressors. Generally, immune and biomineralization of the flounder responded more sensitively to Cd exposure than seawater acidification. Seawater acidification aggravated the toxicological effects of Cd exposure on the two physiological functions, while high Cd exposure augmented their responses to seawater acidification.

Efficacy and side effects of bio-fabricated sardine fish scale silver nanoparticles against malarial vector Anopheles stephensi

Mosquitoes are a great menace for humankind since they transmit pathogenic organisms causing Malaria, Dengue, Chikungunya, Elephantiasis and Japanese encephalitis. There is an urgent need to discover new and novel biological tools to mitigate mosquito-borne diseases. To develop bioinsecticides through newly developed nanotechnology is another option in the present research scenario. In this study we synthesize and characterize sardine fish scales with silver nitrate by adopting various instrumental techniques such as UV- and FTIR-spectroscopy, energy-dispersive X-ray (EDAX), X-ray diffraction analyses (XRD) and scanning electron microscopy (SEM). Toxicity bioassays were conducted with young developmental stages of mosquito vectors. Significant mortality appeared after different life stages of mosquito vectors (young larval and pupal instars were exposed to the nanomaterials). LC50 values were 13.261 ppm for young first instar larvae and 32.182 ppm for pupae. Feeding and predatory potential of G. affinis, before and after exposure to nanoparticles against mosquito larval (I & II) instars of the mosquitoes showed promising results in laboratory experiments. Feeding potential of mosquito fish without nanoparticle treatment was 79.7% and 70.55% for the first and second instar larval populations respectively. At the nanoparticle-exposed situation the predatory efficiency of mosquitofish was 94.15% and 84.3%, respectively. Antioxidant enzymes like (SOD), (CAT), and (LPO) were estimated in the gill region of sardine fish in control and experimental waters. A significant reduction of egg hatchability was evident after nanoparticle application. It became evident from this study that the nano-fabricated materials provide suitable tools to control the malaria vector Anopheles stephensi in the aquatic phase of its life cycle. This finding suggests an effective novel approach to mosquito control.

Comparative responses of Sinopotamon henanense to acute and sub-chronic Cd exposure

Studies on the freshwater crab Sinopotamon henanense have shown that acute and sub-chronic Cd²⁺ exposure induced differential alterations in the respiratory physiology and gill morphology. To elucidate Cd²⁺ toxicity under these two exposure conditions, crabs were acutely exposed to 7.14, 14.28, and 28.55 mg/L Cd²⁺ for 96 h and sub-chronically exposed to 0.71, 1.43, and 2.86 mg/L Cd²⁺ for 3 weeks. The Cd²⁺ accumulation, total metallothionein (MT), superoxide dismutase, and malondialdehyde (MDA) contents in the gill tissues were detected. Moreover, the glucose-6-phosphate dehydrogenase (G6PDH) activity, NADPH content, reduced glutathione (GSH), oxidized glutathione (GSSG), and GSH/GSSG ratio in the hepatopancreas were determined. The morphology of the X-organ-sinus gland complex was also observed. The results showed that sub-chronical Cd²⁺ exposure induced lower MT content and higher MDA level in the gills than in the acute exposure. In the hepatopancreas, acute Cd²⁺ exposure decreased the pentose phosphate pathway activity and NADPH content; however, an increased G6PDH activity and NADPH content were detected in sub-chronic Cd²⁺ exposure (2.86 mg/L). Morphological changes occurred in the sinus gland in crabs exposed to 2.86 mg/L Cd²⁺ for 3 weeks. The tightly packed structure composed by the axons, enlarged terminals, and glial cells, became loose and porous. Ultra-structurally, a large number of vacuoles and few neurosecretory granules were observed in the axon terminal. These effects added to our understanding of the toxic effects of Cd²⁺ and provide biochemical and histopathological evidence for S. henanense as a biomarker of acute or long-term waterborne Cd²⁺ pollution.

Effects of cadmium alone and in combination with pH on bioaccumulation, tissue structure, and enzyme activity of the Chinese mitten crab, Eriocheir sinensis

In this study, Chinese mitten crabs (Eriocheir sinensis) were exposed to various combinations of reduced pH (7.8, 7.3, and 6.5) and cadmium (Cd; 0 and 1 mg·L^-1) for 7, 14, and 21 days. The reduced pH and 1 mg·L^-1 Cd treatment significantly decreased the Cd concentration in crab tissues in the order of pH 7.8 > pH 7.3 > pH 6.5. The exposure to Cd resulted in edema, tubular vacuolization in epithelial cells, and hepatic duct degeneration in the hepatopancreas and indistinct cellular structure and disconnected epithelial layer in the gills. However, low pH alleviated the toxic effects of Cd on the tissues. In gill and hepatopancreas tissues, low pH and Cd exposure caused a significant increase in superoxide dismutase and catalase activities and oxidized glutathione content, but metallothionein activity was not affected. In contrast, the activity of glutathione-S-transferase decreased. Thus, indirect effects of pH on metal accumulation and antagonistic toxicities were observed in E. sinensis, and reduced pH and Cd exposure modulated the oxidative balance via different mechanisms.

Silicone stressed response of crayfish (Procambarus clarkii) in antioxidant enzyme activity and related gene expression

Organosilicon has been widely used in various fields of industry and agriculture due to its excellent properties, such as high and low temperature resistance, flame retardant, insulation, radiation resistance and physiological inertia. However, organosilicon toxicity in aquatic animals is seldom known. In this research, two typical silicone or silane coupling agents (KH-560 (3-Glycidoxypropyltrimethoxysilane) and KH-570 (3-Methacryloxypropyltrimethoxysilane)) were used in a hydroponic experiment to evaluate the effects on survival rate, antioxidant response and gene expression in red swamp crayfish (Procambarus clarkii). Crayfishes were grown in black aquaculture boxes containing different concentrations (0, 10, 100 and 1000 mg L^-1) of KH-560 and KH-570 for 72 h, and then crayfish samples were harvested and separated into tissues of carapace, gill and muscle for analysis. The results showed that silicone significantly increased malondialdehyde (MDA) content in muscle by 17%-38% except for the treatment of 100 mg L^-1 KH-570, and reduced the survival rate of crayfish. Additionally, silicone KH-570 increased the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) by 15%-31%, 17%-35%, and 9%-46%, as well as the contents of ascorbate (AsA) and glutathione (GSH) by 19%-31%, and 23%-29% respectively, in muscle tissue, and similar results occurred in KH-560. In the carapace, however, SOD activity was significantly decreased at high concentrations level of both silicone treatments. Moreover, silicon (Si) content was higher in the abdominal muscle of crayfish after silicone treatment. Assay of gene expression showed an obvious increasing expression of antioxidant related genes (Sod1, Sod2, Cat1, Cat2, and Pod1, Pod2) under silicone stress. The above results suggested that silicone caused an obvious stress response in crayfish in both biochemical and molecular levels.

Reproductive toxicity of quantum dots on gonads of the fresh water crab Sinopotamon henanense

Since nano-quantum dots (QDs) are increasingly used as fluorescent dyes in biomedical sciences, the possibility of QDs contaminating aquatic environments is generally increasing. There is concern about potential toxicity of QDs. However, their risks in the aquatic environment are not entirely understood. In this study, the freshwater crab Sinopotamon henanense was exposed to cadmium telluride (CdTe) QDs by intraperitoneal injection to detect the reproductive toxicity of QDs (1/32, 1/16 and 1/4 LD₅₀; Crab was exposed for 1, 3, 5, and 7 days). After CdTe QD exposure, no significant effect was detected on the body weight and gonadosomatic index. Additionally, morphological observations showed tissue vacuolation in the testis, and inflammatory cell infiltration in the ovary. The submicroscopic structure showed that exposure to CdTe QDs damaged the organelles and cell structures of the gonads of S. henanense. Among the adverse effects, pathological changes in the nuclear membrane, mitochondria and lysosomes were particularly significant. Antioxidant enzymes responded differently to different doses of QDs. The 0.5-mg/kg dose induced superoxide dismutase activity in the testes. And in the 1-mg/kg and 4-mg/kg dose QD exposure test, the testis responded by activating glutathione peroxidase and inducing reduced glutathione and overconsuming glutathione peroxidase. Respectively, the ovaries responded by overconsuming superoxide dismutase and glutathione peroxidase and reduced glutathione. Thus, we conclude that the gonads of S. henanense were injured by CdTe QD, and male are better indicators of the toxicity of QDs than female crabs according to greater alterations in tissue structure and antioxidant enzyme in the analyses.

Oxidative stress in liver of turtle Mauremys reevesii caused by cadmium

The research was designed to examine oxidative stress of the liver of turtle Mauremys reevesii caused by cadmium (Cd). Turtles were injected intraperitoneally with cadmium at the concentration of 7.5, 15, and 30 mg/kg, and 5 turtles were taken from each group after exposure for 1 week (1 w), 2 weeks (2 w), and 3 weeks (3 w). The activities of SOD and CAT as well as the contents of GSH and MDA in liver tissues were detected by using a kit. The results showed that the difference between the control group and the Cd-treated group was statistically significant with the increase of Cd concentration and the prolongation of exposure time, which suggested that Cd caused oxidative stress on the liver of turtles.

A transcriptomics-based analysis of the toxicity mechanisms of gabapentin to zebrafish embryos at realistic environmental concentrations

Gabapentin (GPT) has become an emerging contaminant in aquatic environments due to its wide application in medical treatment all over the world. In this study, embryos of zebrafish were exposed to gabapentin at realistically environmental concentrations, 0.1 μg/L and 10 μg/L, so as to evaluate the ecotoxicity of this emergent contaminant. The transcriptomics profiling of deep sequencing was employed to illustrate the mechanisms. The zebrafish (Danio rerio) embryo were exposed to GPT from 12 hpf to 96 hpf resulting in 136 and 750 genes differentially expressed, respectively. The results of gene ontology (GO) analysis and the Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis illustrated that a large amount of differentially expressed genes (DEGs) were involved in the antioxidant system, the immune system and the nervous system. RT-qPCR was applied to validate the results of RNA-seq, which provided direct evidence that the selected genes involved in those systems mentioned above were all down-regulated. Acetylcholinesterase (AChE), lysozyme (LZM) and the content of C-reactive protein (CRP) were decreased at the end of exposure, which is consistent with the transcriptomics results. The overall results of this study demonstrate that GPT simultaneously affects various vital functionalities of zebrafish at early developmental stage, even at environmentally relevant concentrations.

Effects of cadmium exposure on antioxidant enzymes and histological changes in the mud shrimp Austinogebia edulis (Crustacea: Decapoda)

The trace metal cadmium (Cd) is a toxic pollutant known to induce oxidative stress and other sublethal to lethal effects on aquatic organisms. We exposed the marine mud shrimp Austinogebia edulis to Cd concentrations of 0, 0.5, and 5 mg/kg for up to 4 days (24, 48, 72, 96 h). We studied the activity of antioxidant enzymes in the hepatopancreas, gill, and muscle of A. edulis. Antioxidant enzymes (SOD, CAT, and GPx) decreased with increasing Cd concentration and extended exposure time in these three organs of the mud shrimp A. edulis. Increasing Cd concentration led to an increase in ROS and resulted ultimately in membrane lipid peroxidation at higher Cd concentrations. Significant damage of the hepatopancreas of A. edulis was noticed at higher concentrations of Cd, showing damages like the disappearance of epithelial cell boundaries, detachment of cells from the basal lamina, cellular swelling, necrosis, and reduction of glycogen. In conclusion, Cd caused oxidative damage by reducing the activities of antioxidant enzymes and by damaging the tissue structure in major organs of the mud shrimp A. edulis.

Effect of Cd and Pb Pollutions on Physiological Growth: Wavelet Neural Network (WNN) as a New Approach on Age Determination of Coenobita scaevola

Environmental pollution of aquatic ecosystems leads to an interference in several fundamental biochemical and physiological functions. In this study the interference of Cd and Pb pollutions on the physiological growth and subsequently on the age determination was investigated. The hermit crab, Coenobita scaevola (C.s) was selected as a bioaccumulator in this study. The direct and indirect age determination methods were carried out using annual band counts and carapace length, respectively. The results showed that, there was very low correlation (R² < 0.5) between direct and indirect age determination. Wavelet Neural Network (WNN) was applied to take into account the environmental effects such as the accumulation of Cd and Pb elements in the C.s' tissues. It was observed that WNN successfully enhanced the growth rate model and estimated the C.s' age (R² > 0.95). In addition, it was concluded that the environmental pollution had interaction with the growth physiology such as weight and length.