Growth and health status of Pacific white shrimp, Litopenaeus vannamei, exposed to chronic water born cobalt

Plantago asiatica seed as a protective agent for mitigating metals toxicity on Penaeusvannamei

Plantago asiatica seeds (PS) are commonly used as a medicinal plant. This study investigates the efficacy of PS against heavy metal toxicity in white shrimp (Penaeus vannamei). After feeding PS diet (5 g/kg) or basal diet (control group) for 7 days, shrimps were exposed to sublethal concentrations of heavy metals in seawater (As: 12 mg/L, Pb: 250 mg/L, Hg: 0.4 mg/L). The 7-day survival observation showed that the survival in groups fed with PS were significantly higher than that in the control group, revealing that dietary PS had the efficacy to mitigate heavy metal toxicity in white shrimp. Under the same feeding condition, white shrimps were exposed to safety dose of heavy metals (1/10 of sublethal concentrations) to understand the mechanism of mitigation. The metal accumulations in haemolymph, gills, hepatopancreas, and muscle tissues as well as the immune, anti-oxidative, stress related gene expressions in haemocytes, gills and hepatopancreas were measured for 14 days. The As accumulation in gills and hepatopancreas of groups fed with PS were significantly lower than those of control group on day 7 and 14, respectively; The Pb concentration in haemolymph of group fed with PS was significantly lower than that of control group on day 7 and 14; The Hg concentration in hepatopancreas of the group fed with PS was significantly lower than that of control group on day 7. Dietary PS could mitigate heavy metal-induced immune suppression, oxidative stress, and stress response by positively regulating immune (proPO I, Toll, IMD), antioxidant (SOD, GST, Trx), and negatively regulating stress response genes (HSP70, MT). The present study demonstrated that dietary PS could protect white shrimp against metal toxicity by reducing metal accumulations and regulating the immune, antioxidant, and stress response gene expressions in specific tissue. Therefore, PS may serve as a beneficial feed additive in the aquaculture.

Toxic effects and mechanisms of chronic cadmium exposure on Litopenaeus vannamei growth performance based on combined microbiome and metabolome analysis

Cadmium (Cd) pollution seriously affects marine organisms' health and poses a threat to food safety. Although Cd pollution has attracted widespread attention in aquaculture, little is known about the toxic mechanisms of chronic Cd exposure on shrimp growth performance. The study investigated the combined effects of chronic exposure to Cd of different concentrations including 0, 75, 150, and 300 μg/L for 30 days on the growth performance, tissue bioaccumulation, intestinal microbiology, and metabolic responses of Litopenaeus vannamei. The results revealed that the growth was significantly inhibited under exposure to 150 and 300 μg/L Cd2+. The bioaccumulation in gills and intestines respectively showed an increasing and inverted "U" shaped trend with increasing Cd2+ concentration. Chronic Cd altered the intestinal microflora with a significant decrease in microbial richness and increasing trends in the abundances of the potentially pathogenic bacteria Vibrio and Maribacter at exposure to 75 and 150 μg/L Cd2+, and Maribacter at 300 μg/L. In addition, chronic Cd interfered with intestinal metabolic processes. The expressions of certain metabolites associated with growth promotion and enhanced antioxidant power, including N-methyl-D-aspartic acid, L-malic acid, guanidoacetic acid, betaine, and gluconic acid were significantly down-regulated, especially at exposure to 150 and 300 μg/L Cd2+, and were negatively correlated with Vibrio and Maribacter abundance levels. In summary, chronic Cd exposure resulted in severe growth inhibition and increased Cd accumulation in shrimp tissues. Increased levels of intestinal pathogenic bacteria and decreased levels of growth-promoting metabolites may be the key causes of growth inhibition. Harmful bacteria Vibrio and Maribacter may be associated with the inhibition of growth-promoting metabolite expression and may be involved in disrupting intestinal metabolic functions, ultimately impairing shrimp growth potential. This study sheds light on the potential toxicological mechanisms of chronic Cd inhibition on shrimp growth performance, offering new insights into Cd toxicity studies in aquaculture.

Considerations for fatty acids in standardized reference diet for parthenogenetic marbled crayfish Procambarus virginalis model organism

Fatty acid accumulation was studied in the parthenogenetic all-female marbled crayfish Procambarus virginalis using six arbitrarily designed experimental feeds and related to individuals with glair glands (sexual maturity) after 100 days of ad libitum feeding at 21 °C, including gravid females from the wild as a reference. Fatty acids 16:0 and 18:1n-9 comprised 40% of the total amount of fatty acids and tended to up-concentrate in bodies. Shorter chain 14:0 depleted from feed to body. Across diets, there was a concomitant decrease in precursor fatty acid and increase in product fatty acid, such as reinforcements in monounsaturated fatty acid (18:1n-9), eicosanoid precursors 20:4n-6 (arachidonic acid, ARA) and 20:5n-3 (eicosapentaenoic acid, EPA) in-vivo, but not 22:6n-3 (docosahexaenoic acid, DHA) except when deficient in CHI or CHI + SPI diets. Saturation kinetics modeling (R2 0.7-0.9, p < 0.05) showed that when the ARA share is ~ 1%, the EPA share is ~ 8%, and the DHA share is ~ 2% in the food lipids, the accumulation of fatty acids in body lipids levels off. The lowest DHA in the CHI (0% glair glands) or CHI + SPI (0-3.9% glair glands) diets, and the lowest ARA in SER (0% glair glands) or SER + SPI (0-3% glair glands) diets, were synchronous with negligible sexual maturity despite a wide range of observed specific growth rates (2.77-3.60% per day), body size (0.44-0.84 g), ≤ 5% crude lipid and 40-46% crude protein feed. The FISH and SHRIMP diets (56% protein, 11-14% lipid) with the highest ARA, EPA, and DHA together seem to be the most conducive diets for sexual maturity (up to 20% of individuals with glair glands). We propose a fatty acid profile mimicking the FISH or SHRIMP diets as a starting point for designing the lipid content required in the marbled crayfish standardized reference diet.

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.

A Comprehensive Review on the Roles of Metals Mediating Insect-Microbial Pathogen Interactions

Insects and microbial pathogens are ubiquitous and play significant roles in various biological processes, while microbial pathogens are microscopic organisms that can cause diseases in multiple hosts. Insects and microbial pathogens engage in diverse interactions, leveraging each other's presence. Metals are crucial in shaping these interactions between insects and microbial pathogens. However, metals such as Fe, Cu, Zn, Co, Mo, and Ni are integral to various physiological processes in insects, including immune function and resistance against pathogens. Insects have evolved multiple mechanisms to take up, transport, and regulate metal concentrations to fight against pathogenic microbes and act as a vector to transport microbial pathogens to plants and cause various plant diseases. Hence, it is paramount to inhibit insect-microbe interaction to control pathogen transfer from one plant to another or carry pathogens from other sources. This review aims to succinate the role of metals in the interactions between insects and microbial pathogens. It summarizes the significance of metals in the physiology, immune response, and competition for metals between insects, microbial pathogens, and plants. The scope of this review covers these imperative metals and their acquisition, storage, and regulation mechanisms in insect and microbial pathogens. The paper will discuss various scientific studies and sources, including molecular and biochemical studies and genetic and genomic analysis.

Photocatalytic degradation of norfloxacin by magnetic molecularly imprinted polymers: influencing factors and mechanisms

Novel magnetic molecularly imprinted polymers (MMIP) were prepared for selective removal of norfloxacin by effectively utilizing photocatalytic degradation and magnetic separation techniques. The imprinted material with titanium layer and multihole surface showed an excellent photocatalytic property. In this paper, the kinetics of photocatalytic degradation of norfloxacin by MMIP was explored, and the influences of environmental factors, including solution pH, humic acid, common ions and water media on photocatalytic performance of MMIP were elucidated. The results showed that MMIP had good adaptability and could degrade norfloxacin within 60 min, but the degradation rate constant decreased in surface water. Based on the identification of intermediate products, the possible degradation pathways of norfloxacin were analysed, speculating that it might be degraded into small molecules in the form of de-piperazine ring, de-carboxyl group and de-fluorine. Moreover, the mineralization ratio of norfloxacin could reach 84.2% after ultraviolet irradiation for 150 min, and the low cobalt release of MMIP enhanced the security of the material. The results of adsorption and degradation cycle tests showed that MMIP obtained by molecular imprinting technology had excellent performance in sustainable use for micro organic pollutants removal.

Copper-mediated shifts in transcriptomic responses of intestines in Bufo gargarizans tadpoles to lead stress

The differential transcriptomic responses of intestines in Bufo gargarizans tadpoles to Pb alone or in the presence of Cu were evaluated. Tadpoles were exposed to 30 μg/L Pb individually and in combination with Cu at 16 or 64 μg/L from Gosner stage (Gs) 26 to Gs 38. After de novo assembly, 105,107 unigenes were generated. Compared to the control group, 7387, 6937, and 11139 differentially expressed genes (DEGs) were identified in the treatment of Pb + Cu0, Pb + Cu16, and Pb + Cu64, respectively. In addition, functional annotation and enrichment analysis of DEGs revealed substantial transcriptional reprogramming of diverse molecular and biological pathways were induced in all heavy metal treatments. The relative expression levels of genes associated with intestinal epithelial barrier and bile acids (BAs) metabolism, such as mucin2, claudin5, ZO-1, Asbt, and Ost-β, were validated by qPCR. This study demonstrated that Pb exposure induced transcriptional responses in tadpoles, and the responses could be modulated by Cu.

Integrative time series of cellular, humoral and molecular response revealed immunotoxicity of bifenthrin to Chinese rare minnow (Gobiocypris rarus) following Pseudomonas fluorescens challenge

Bifenthrin is a common pesticide that is widespread in aquatic environments. Although it has been shown to be toxic to aquatic organisms, its immunotoxicity and mechanism are unclear. Herein, we reported the immunotoxicity of bifenthrin on adult Chinese rare minnow (Gobiocypris rarus) after 28 days of exposure to different concentrations of bifenthrin (0.1, 0.3, and 1.0 μg/L) and 36-h Pseudomonas fluorescens challenge. Bifenthrin inhibited the fish humoral immune response to bacteria by altering the lymphocyte and neutrophil ratios and decreasing the production of lysozyme, complement component 3, immunoglobulin M, and C-reactive protein, particularly were 1.0 μg/L. Bifenthrin caused intestinal damage and significantly reduced the volume of intestinal mucus at 12 and 36 hours postinjection (hpi) (p < 0.05). Moreover, 1.0 μg/L bifenthrin significantly increased the fish mortality and bacterial loads at 12 and 36 hpi (p < 0.05). RNA-seq analysis revealed several enriched genes involved in pathogen attachment and recognition, inflammatory responses, and complement system at the early-to-mid stage of infection (4-12 hpi). Overall, our results corroborated that bifenthrin induced immunotoxicity in Gobiocypris rarus, resulting in immune dysfunction of fish and increasing their sensitivity to bacterial infection and accelerating mortality. Moreover, 4-12 hpi was better than 36 hpi for analyzing immune responses against pathogen infection in fish exposed to bifenthrin.

Toxicity of chronic waterborne zinc exposure in the hepatopancreas of white shrimp Litopenaeus vannamei

Zinc (Zn) is necessary for the survival of aquatic organisms; nevertheless, the accumulation of Zn in excessive amounts may have toxic consequences. Few studies focusing on the biochemical, morphological, and transcriptional effects of aqueous Zn in Litopenaeus vannamei have been reported, and the underlying toxic mechanism remains largely unknown. The present study was performed to investigate the growth performance, morphological alterations, physiological changes, and transcriptional responses after Zn exposure at 0 (control), 0.01, 0.1, and 1 mg/L concentrations for 30 days in white shrimp L. vannamei hepatopancreas. The results found that survival rate (SR) and growth performance were significantly reduced in 1 mg/L Zn group. Significant structural damage and significant Zn accumulation in hepatopancreas were observed. The activities of trypsin and amylase (AMS), and the total antioxidant capacity (T-AOC) were attenuated, while the production of reactive oxygen species (ROS) and malondialdehyde (MDA) content were significantly increased after Zn exposure. Many differentially expressed genes (DEGs) were obtained after Zn exposure, and the majority of these DEGs were downregulated. Ten DEGs involved in oxidative stress, immunological response, apoptosis, and other processes were selected for qRT-PCR validation and the expression profiles of these DEGs kept well consistent with the transcriptome data, which confirmed the accuracy and reliability of the transcriptome results. Subsequently, we screened 12 genes to examine the changes of expression in different concentrations in more detail. All the results implying that Zn exposure caused severe histopathological changes and increased Zn accumulation in hepatopancreas, altered immune, antioxidant and detoxifying response by regulating the gene expressions of related genes, and eventually might trigger apoptosis. These findings provide valuable information and a new perspective on the molecular toxicity of crustaceans in response to environmental heavy metal exposure.

Exploring the interactions between the gut microbiome and the shifting surrounding aquatic environment in fisheries and aquaculture: A review

The rise of "new" sequencing technologies and the development of sophisticated bioinformatics tools have dramatically increased the study of the aquaculture microbiome. Microbial communities exist in complex and dynamic communities that play a vital role in the stability of healthy ecosystems. The gut microbiome contributes to multiple aspects of the host's physiological health status, ranging from nutritional regulation to immune modulation. Although studies of the gut microbiome in aquaculture are growing rapidly, the interrelationships between the aquaculture microbiome and its aquatic environment have not been discussed and summarized. In particular, few reviews have focused on the potential mechanisms driving the alteration of the gut microbiome by surrounding aquatic environmental factors. Here, we review current knowledge on the host gut microbiome and its interrelationship with the microbiome of the surrounding environment, mainly including the main methods for characterizing the gut microbiome, the composition and function of microbial communities, the dynamics of microbial interactions, and the relationship between the gut microbiome and the surrounding water/sediment microbiome. Our review highlights two potential mechanisms for how surrounding aquatic environmental factors drive the gut microbiome. This may deepen the understanding of the interactions between the microbiome and environmental factors. Lastly, we also briefly describe the research gaps in current knowledge and prospects for the future orientation of research. This review provides a framework for studying the complex relationship between the host gut microbiome and environmental stresses to better facilitate the widespread application of microbiome technologies in fisheries and aquaculture.

The Optimum Lipid Level for the Juvenile Redclaw Crayfish Cherax quadricarinatus: Practical Diets with Soybean Oil as the Lipid Source

As a new species in aquaculture, the lipid nutrition requirement for the juvenile redclaw crayfish Cherax quadricarinatus on a dietary basis on a practical formula needs to be evaluated accurately. In this study, the optimum dietary lipid level was explained by analyzing the growth performance, antioxidant state, lipid metabolism, and gut microbiota of C. quadricarinatus after an eight-week cultivation trial. Six diets with different soybean oil levels (named L0, L2, L4, L6, L8, and L10) were fed to C. quadricarinatus (11.39 ± 0.28 g). The results indicated that the specific growth rate and weight gain of crayfish fed the L4 and L6 diets were significantly higher than those of the other groups (P < 0.05). By the analysis of a second-order polynomial regression model according to growth performance (weight gain rate), the optimum lipid level in a practical diet for juvenile C. quadricarinatus was 9.67%. The survival, condition factor, and hepatosomatic index of crayfish were not significantly affected by dietary oil levels (P > 0.05). As the level of dietary lipids increased, the total antioxidant capacity and glutathione peroxidase activity in serum showed a tendency to rise and then fall and the enzyme activity was highest in crayfish fed the L6 diet. Gut lipase and pepsin activities showed the highest value in crayfish fed the L6 diet. There was no significant difference in acetyl-CoA carboxylase and carnitine palmitoyltransferase-1 contents in crayfish among all the groups (P > 0.05). The relative abundance of Proteobacteria in the phylum and Citrobacter in the genus showed a significant decrease in crayfish of the L10 diet, while the relative abundance of Firmicutes in the phylum markedly increased compared to that of the other groups (P < 0.05). In summary, the results indicated that the 10.39% (L6 diet) dietary lipid level could induce better growth performance, antioxidant ability, and digestive enzyme activity. Most of the fatty acid composition of muscle is not closely related to the fatty acid composition of the diet. Moreover, the composition and diversity of the gut microbiota of C. quadricarinatus were changed by high dietary lipid levels.

Transcriptomic and proteomic analysis of Chinese rare minnow (Gobiocypris rarus) larvae in response to acute waterborne cadmium or mercury stress

In this study, Chinese rare minnow (Gobiocypris rarus) larvae were exposed to the control group, Cd concentrations (0.5 and 2.5 mg/L), and Hg concentrations (0.1 and 0.3 mg/L) for 96 h. Transcriptome analysis showed that 816 and 1599 significantly differentially expressed genes (DEGs) were identified in response to 2.5 mg/L Cd²⁺ and 0.3 mg/L Hg²⁺, respectively. Functional enrichment analysis revealed that DEGs were mostly associated with immune responses after Cd exposure, such as antigen processing and presentation, phagosome, apoptosis, and lysosome. Similarly, functional enrichment analysis showed that many pathways were mostly involved in metabolism after Hg exposure, such as glutathione metabolism and starch and sucrose metabolism. Results of two-dimensional electrophoresis (2-DE) showed that the abundance of 10 protein spots was significantly altered in the Cd²⁺ treatments. The proteomic analysis demonstrated that Cd toxicity might impair cytoskeletal and cell motility-related protein activity in the liver of G. rarus. Similarly, the abundance of 24 protein spots was significantly altered in the Hg²⁺ treatments. Hg toxicity regulates the expression of proteins belonging to several functional categories, including cytoskeleton, oxidative stress, digestive system, and energy metabolism. This study provides valuable relevant insight into the molecular mechanisms in response to Cd or Hg toxicity in aquatic organisms and will help screen for potential biomarkers to respond to Cd and Hg pollutants.

Impact of imidacloprid exposure on the biochemical responses, transcriptome, gut microbiota and growth performance of the Pacific white shrimp Litopenaeus vannamei

The widespread use of neonicotinoid insecticides, such as imidacloprid, in agriculture is one of the key factors for the drop in the survival of invertebrates, including decapod crustaceans. However, there is currently a lack of comprehensive studies on the chronic toxicity mechanisms in decapod crustaceans. Here, the concentration-dependent effects of imidacloprid on the physiology and biochemistry, gut microbiota and transcriptome of L. vannamei , and the interaction between imidacloprid, gut microbiota and genes were studied. Imidacloprid caused oxidative stress, leading to reduced growth and to immunity and tissue damage in L. vannamei . Imidacloprid increased the gut pathogenic microbiota abundance and broke the steady state of the gut microbiota interaction network, resulting in microbiota function disorders. Chronic imidacloprid exposure induced overall transcriptome changes in L. vannamei . Specifically, imidacloprid caused a large number of differentially expressed genes (DEGs) to be significantly downregulated. The inhibition of autophagy-related pathways revealed the toxic process of imidacloprid to L. vannamei . The changes in phase I and II detoxification gene expression clarified the formation of a detoxification mechanism in L. vannamei . The disturbance of circadian rhythm (CLOCK) caused by imidacloprid is one of the reasons for the increase in gut pathogenic microbiota abundance.

Effect of polyethylene microplastics on oxidative stress and histopathology damages in Litopenaeus vannamei

There has been a significant increase in the microplastic (MP) polluting the ocean in recent time which is regarded as toxic for living organisms. In this study, Fluorescent red polyethylene microspheres (FRPE) were administered intramuscularly to Litopenaeus vannamei juveniles at the concentration of 0.1, 0.2, 0.5 and 1.0 μg (g shrimp)^-1, and the survival rate was recorded. Analysis of the hepatopancreas for antioxidant enzyme activity and gene expression were done after seven days. Further tissue morphology and accumulation of FRPE was analysed. The results showed that FRPE at 0.5 and 1.0 μg (g shrimp)^-1 reduce the survival rate of L. vannamei. FRPE at 0.5 and 1.0 μg (g shrimp)^-1 reduced superoxide dismutase (SOD) activity; FRPE at different concentrations reduced catalase (CAT) activity; FRPE at 0.2, 0.5 and 1.0 μg (g shrimp)^-1 increased the lipid peroxide thiobarbituric acid (TBARS) content. FRPE at 0.1, 0.2, and 0.5 μg (g shrimp)^-1 significantly affect the performance of SOD and CAT genes; FRPE at 0.2 and 0.5 μg (g shrimp)^-1 significantly improves GPx gene performance; FRPE at 1.0 μg (g shrimp)^-1 significantly reduced the expression of GPx genes. Analysis of tissue morphology shows that FRPE cause muscle, midgut gland, and hepatopancreas, and gill damage at different concentrations. In the results of accumulation of microplastic, FRPE accumulated in gill tissue at 0.2 and 0.5 μg (g shrimp)^-1; FRPE accumulated in gill, muscle and hepatopancreas tissue at 1.0 μg (g shrimp)^-1. Based on the above results, FRPE at 0.5 and 1.0 μg (g shrimp)^-1 can regulate the antioxidant enzymes of L. vannamei, increase lipid peroxide content, cause tissue damage by accumulating in the tissues. The rate of survival decreased in L. vannamei, and the impact of FRPE at 1.0 μg (g shrimp)^-1 was significant.

Effects of Quercetin on Acrylamide-Induced Variation of Serum Elements in Rats

Acrylamide (AA) is an organic chemical widely existing in the public diet, especially in foods with high-temperature fried and baked starchy and may have various adverse health effects on organisms. The purpose of this study was to investigate whether quercetin plays a protective role in AA-induced element variation in rats. Rats were randomly divided into the control group, AA-treated group [5 mg/kg body weight (bw)], two dosages of quercetin-treated groups (10 and 50 mg/kg·bw, respectively), and two dosages of quercetin plus AA-treated groups. After a 16-week treatment, the serum samples of rats were collected. Serum elements were analyzed by using inductively coupled plasma mass spectrometry (ICP-MS) combined with multivariate statistical analysis, and antioxidant indices, lipid peroxidation indicator, as well as inflammatory biomarkers, were also detected. The accuracy and precision of the method were verified, and all the validated data are within the satisfactory range. The results showed that the levels of vanadium (V), copper (Cu), zinc (Zn), selenium (Se), cobalt (Co), and magnesium (Mg) in serum were significantly lower (p < 0.01), while serum calcium (Ca) level was significantly higher (p < 0.01) in AA-treated group compared with the control group. When high-dose quercetin was administered to rats combined with AA, a significant recovered effect for the above elements levels was observed compared with the AA-treated group. This study suggests that quercetin (50 mg/kg·bw) exerts a regulatory and protective role in AA-induced variation of serum elements via reducing oxidative stress and inhibiting inflammation.

Effects of metal ions on activity and structure of phenoloxidase in Penaeus vannamei

Phenoloxidase (PO) is a typical metal enzyme, which requires metal ions as prosthetic groups to enable the full exertion of its activity. To study how metal ions affected the activity and structure of PO enzymes, while providing reference materials for in-depth investigations, we examined the effects of different metal ions (Cu²⁺, Zn²⁺, Mg²⁺, Ca²⁺, and Ba²⁺) on their activities. Furthermore, Cu²⁺ and Mg²⁺ were selected for further investigation through UV spectra, intrinsic fluorescence spectroscopy, AFM, and FTIR. It was revealed that Cu²⁺ had a more obvious effect on PO compared to Mg²⁺. The PO could be activated when the concentrations of Cu²⁺ and Mg²⁺ were lower than 10^-3 and 10^-2 mol/L, respectively, and maximum PO activities (182.14% and 141.02%) were observed at 10^-4 mol/L concentrations of Cu²⁺ and Mg²⁺. When the concentrations of Cu²⁺ and Mg²⁺ were higher than 10^-2 and 10^-1 mol/L, the activities PO were inhibited. The results of the UV-vis and fluorescence spectra revealed that Cu²⁺ shaped the tertiary structure of PO, whereas the effect of Mg²⁺ was slight. The AFM results demonstrated that high concentrations of Cu²⁺ and Mg²⁺ resulted in PO aggregation. FTIR analysis indicated that the total content of PO α-helices and β-sheets decreased with higher concentrations of Cu²⁺ and Mg²⁺.

Effects of ZnO nanoparticles on the Giant freshwater prawn (Macrobrachium rosenbergii, de Man, 1879): Reproductive performance, larvae development, CHH concentrations and anti-oxidative enzymes activity

The Giant freshwater prawn (Macrobrachium rosenbergii) breeds when in captive conditions. The eggs of a clutch are attached to the abdomen of berried females. Zinc oxide (ZnO) is one of the most important metal oxide-nanoparticles (NPs) that is widely used in various industries and is released into aquatic environments from wastewater management facilities. The present study was conducted to evaluate effects of ZnO on values for the reproductive variables: larvae development, crustacean hyperglycemic hormone (CHH) release from the X-organ into the hemolymph and anti-oxidative enzymes activity of M. rosenbergii. There were five groups including a group not treated (control), and groups treated with10, 20, 50, 100 mg/L ZnO in triplicate during a 90-day period. Results indicated that ZnO-NPs have marked effects on reproductive performance, offspring development, CHH release from the X-organ into the hemolymph and anti-oxidant enzymes activities with there being no spawning of brood-stock in the 100 mg/L ZnO group and in the prawns treated with 50 mg/L there was spawning but there was larvae mortality immediately subsequent to hatching. Also, values for viability rate of eggs, dry weight of eggs, brood-stock inter-spawn period and egg clutch somatic index (ESI) reproductive variables were affected by the NP. This NP was found to have a dose-dependent effect on CHH release from the X-organ into the hemolymph and also superoxide dismutase (SOD) and catalase activities in M. rosenbergii. The results indicate that M. rosenbergii, a freshwater decapod crustacean, is an appropriate species to study nano-material effects on reproduction in freshwater ecosystems.