Comparative assessment of the antioxidative defense system in subadult and adult anurans: A lesson from the Bufotes viridis toad

Evaluating the Effects of Replacing Alfalfa with Broussonetia papyrifera Branch/Leaf Powder on Growth and Serum Indicators in Dezhou Donkeys

The purpose of this experiment was to study the apparent digestibility and the effects of Broussonetia papyrifera (BP) branch/leaf powder supplementation on growth performance and serum indicators in donkeys. The results showed that the apparent digestibility of dry matter (DM), crude protein (CP), crude fiber (CF), neutral detergent fiber (NDF), acidic detergent fiber (ADF), and digestible energy content (DE) of BP branch/leaf powder were 51.88%, 67.27%, 64.86%, 49.59%, 54.73%, 40.87%, and 6.37 MJ/kg, respectively. The average daily gain (ADG) in the 20% group was significantly higher than in the 0% and 30% groups. The serum albumin (ALB) levels in the 0% and 10% groups were significantly higher than those in the 20% and 30% groups, while the serum globulin (GLB) content in the 10% group was significantly lower than in the other groups. The 20% group showed decreased serum triglyceride (TG) levels compared to the other groups. Both the 20% and 30% groups exhibited lower total cholesterol (TC) levels and increased alanine aminotransferase (ALT) compared to the 0% and 10% groups and higher serum lactate dehydrogenase (LDH) levels than the 10% group. The 30% group had higher serum immunoglobulin A (IgA) levels than the other groups, while all three BP branch/leaf powder groups had lower serum tumor necrosis factor (TNF-α) levels than the 0% group. There was a gradual increase in serum total antioxidant capacity (T-AOC) with the increasing amount of BP branch/leaf powder added. In conclusion, the optimal supplemental proportion of BP branch/leaf powder in the diet is 20%. Furthermore, BP branch/leaf powder can improve growth performance, serum immune indices, and antioxidant capacity in Dezhou donkeys.

Changes of oxidative status in yellowfin seabream larvae (Acanthopagrus latus) during development

Dynamic changes of tissues, organs and growth that occur in fish larvae during the transition to the juvenile stage are accompanied by differences in metabolic, locomotor and feeding activities that can reflect on fish's oxidative status. In this study, we examine how body growth, antioxidant system (superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and total antioxidant capacity (TAC) and oxidative damage (malondialdehyde-MDA) parameters change in larvae of yellowfin seabream larvae (Acanthopagrus latus) during early development (0, 7, 15, 22 and 30 day after hatching-DAH). Body growth (length and weight) starts to intensify from 15 DAH. We observed general increase in the antioxidant system (AOS) with the age of larvae from newly hatched and 7 DAH up to 15 and 22 DAH individuals. 15 and 22 DAH larvae had the greatest levels of TAC, SOD and GR activity, while 30 DAH larvae had higher CAT activity from 0, 7 and 15 DAH and MDA concentration in comparison to 15 DAH individuals. Several developmental events can be linked with observed results: lower AOS in 0 and 7 DAH individuals with low locomotor activity, growth, endo-exogenous feeding phase and cell differentiation; 15 and 22 DAH larvae are under pressure of fast growth, enhanced swimming and foraging capacity; while higher MDA production in 30 DAH larvae can be a result of shifts in muscle metabolism, changes in both quality and quantity of food and a significant increase in weight. The present study provides insight into the changes in redox status during the ontogeny of A. latus, fish species about which physiology is still little known but with a potential for use in marine culture. Ability to lower oxidative stress during critical developmental periods can enhance that potential.

Toxicological effects of Saponin on the free larval stages of Schistosoma mansoni, infection rate, some biochemical and molecular parameters of Biomphalaria alexandrina snails

Saponins have been used as biopesticides. The objective of the present study is to investigate the toxic effects of Saponin against Biomphalaria alexandrina snails. Results showed that Saponin exhibited a molluscicidal activity against adult B. alexandrina snails at LC₅₀ (70.05 mg/l) and had a larvicidal effect on the free larval stages of Schistosoma mansoni. To evaluate the lethal effects, snails were exposed to either LC₁₀ (51.8 mg/l) or LC₂₅ (60.4 mg/l) concentrations of Saponin. The survival, the infection rates, protein, albumin, and total fat levels were decreased, while glucose levels were increased in exposed snails compared to control snails. Also, these concentrations significantly raised Malondialdehyde (MDA) and Glutathione S Transferase (GST) levels, whereas reduced Superoxide dismutase (SOD) activity and the total antioxidant capacity (TAC) in exposed snails. Furthermore, these concentrations resulted in endocrine disruptions where it caused a significant increase in testosterone (T) level; while a significant decrease in Estradiol (E2) levels were noticed. As for Estrogen (E) level, it was increased after exposure to LC₁₀ Saponin concentration while after exposure to LC₂₅ concentration, it was decreased. Also, LC₁₀ and LC₂₅ concentrations of Saponin caused a genotoxic effect and down-regulation of metabolic cycles in the snails. In conclusion, Saponins caused deleterious effects on the intermediate host of schistosomiasis mansoni. Therefore, B. alexandrina snails could be used as models to screen the toxic effects of Saponins in the aquatic environment and if it was used as a molluscicide, it should be used cautiously and under controlled circumstances.

Effect of a Plateau Environment on the Oxidation State of the Heart and Liver through AMPK/p38 MAPK/Nrf2-ARE Signaling Pathways in Tibetan and DLY Pigs

This study evaluated the effect of a plateau environment on the heart and liver oxidation state of Tibetan pigs (TPs) and DLY pigs through analyzing AMPK, p38 MAPK, and Nrf2 signaling pathways. Twelve 120-day-old TPs and twelve 120-day-old DLY pigs were randomly divided into two groups in a plateau environment for three weeks. Exposed to a plateau environment, TPs exhibited a lower (p < 0.05) malondialdehyde level but higher (p < 0.05) glutathione, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and total antioxidant capacity (T-AOC) activities in the liver and heart than those observed in DLY pigs. TPs also showed higher (p < 0.05) mRNA levels of SOD and GSH-Px in the liver and heart compared with those of DLY pigs. The TPs showed higher (p < 0.05) mRNA and protein levels of AMPK and Nrf2 in the liver and heart compared with those of DLY pigs. Furthermore, TPs showed higher (p < 0.05) mRNA and protein levels of p38 MAPK in the heart and higher mRNA levels of p38 MAPK in the liver compared with those of DLY pigs under a plateau environment. In summary, TPs possess a stronger antioxidant capacity in the heart and liver than that of DLY pigs in a plateau environment through AMPK/p38 MAPK/Nrf2-ARE signaling pathways.

Effects of Separate and Combined Exposure of Cadmium and Lead on the Endochondral Ossification in Bufo gargarizans

Cadmium (Cd) and lead (Pb) are ubiquitous in aquatic environments and most studies have examined the potential effects of Cd or Pb alone on aquatic organisms. In the present study, chronic effects of Cd and Pb, alone and in combination, on Bufo gargarizans were investigated by exposing embryos to these contaminants throughout metamorphosis. Significant reductions in body mass and snout-to-vent length were observed in B. gargarizans at Gosner stage 42 (Gs 42) and Gs 46 exposed to a Cd/Pb mixture. Single and combined exposure with Cd and Pb induced histological alterations of the thyroid gland characterized by reduced colloid area and thickness of epithelial cells. There was a significant decrease in the maximum jump distance of froglets exposed to Cd alone and the Cd/Pb mixture, and the jumping capacity showed a positive correlation with hind limb length and tibia/fibula. Moreover, single metals and their mixture induced reduction of endochondral bone formation in B. gargarizans. Transcriptomic and real-time quantitative polymerase chain reaction results showed that genes involved in skeletal ossification (TRα, TRβ, Dio2, Dio3, MMP9, MMP13, Runx1, Runx2, and Runx3) were transcriptionally dysregulated by Cd and Pb exposure alone or in combination. Our results suggested that despite the low concentration tested, the Cd/Pb mixture induced more severe impacts on B. gargarizans. In addition, the Cd/Pb mixture might reduce chances of survival for B. gargarizans froglets by decreasing size at metamorphosis, impaired skeletal ossification, and reduction in jumping ability, which might result from dysregulation of genes involved in thyroid hormone action and endochondral ossification. The findings obtained could add a new dimension to understanding of the mechanisms underpinning skeletal ossification response to heavy metals in amphibians. Environ Toxicol Chem 2022;41:1228-1245. © 2022 SETAC.

Stress Response, Immunity, and Organ Mass in Toads (Rhinella diptycha) Living in Metal-Contaminated Areas

Mining is one of the main activities that drive the economy of Brazil. Mining activity is associated with risk of contamination of environment and local fauna by metals. Amphibians have a life cycle that requires a transition between aquatic and terrestrial environments, increasing their vulnerability to metal contamination in the water and substrate. Metals are ubiquitous, with high bioaccumulative and biomagnifying potential, and may lead to immune and endocrine disruption. In this study, we analyzed two different components of the innate immune response, bacterial killing ability (BKA) and phytohemagglutinin edema (PHA), and two stress biomarkers, corticosterone plasma levels (CORT) and the neutrophil to lymphocyte ratio (N:L), of toads (Rhinella diptycha) living in places contaminated by metals. Blood samples were collected pre- and post-restraint (1h), followed by an immune challenge with PHA and tissue collection (liver, spleen, and kidneys). Toads liver metal bioaccumulation did not correlate with the immune response or stress biomarkers. Post-restraint, animals had increased CORT and reduced BKA, independently of the collection site, and these variables were not correlated with liver metal bioaccumulation. Interestingly, toads with the larger spleen (immune organ) showed increased N:L post-restraint and greater edema after the PHA challenge. Our results indicate that toads living in metal-contaminated environments responded to acute stressor, activating the hypothalamic-pituitary-interrenal axis and the immune response. Keep tracking the physiological variables of these animals and the presence of metals in the environment and tissues should provide valuable health status indicators for the population, which is vital for proposing amphibian conservation strategies in these areas.

Oxidative Stress Parameters in Goitrogen-Exposed Crested Newt Larvae (Triturus spp.): Arrested Metamorphosis

Thiourea is an established disruptor of thyroid hormone synthesis and is frequently used as an inhibitor of metamorphosis. The changes caused by thiourea can affect processes associated with the oxidative status of individuals (metabolic rate, the HPI axis, antioxidant system). We investigated the parameters of oxidative stress in crested newt (Triturus spp.) larvae during normal development in late larval stage 62 and newly metamorphosed individuals, and during thiourea-stimulated metamorphosis arrest in individuals exposed to low (0.05%) and high (0.1%) concentrations of thiourea. Both groups of crested newts exposed to thiourea retained their larval characteristics until the end of the experiment. The low activities of antioxidant enzymes and the high lipid peroxidation level pointed to increased oxidative stress in larvae at the beginning of stage 62 as compared to fully metamorphosed individuals. The activities of catalase (CAT) and glutathione-S-transferase (GST) and the concentration of sulfhydryl (SH) groups were significantly lower in larvae reared in aqueous solutions containing thiourea than in newly metamorphosed individuals. The high thiourea concentration (0.1%) affected the antioxidative parameters to the extent that oxidative damage could not be avoided, contrary to a lower concentration. Our results provide a first insight into the physiological adaptations of crested newts during normal development and simulated metamorphosis arrest.

Studying microplastics: Lessons from evaluated literature on animal model organisms and experimental approaches

Although we are witnesses of an increase in the number of studies examining the exposure/effects of microplastics (MPs) on different organisms, there are many unknowns. This review aims to: (i) analyze current studies devoted to investigating the exposure/effects of MPs on animals; (ii) provide some basic knowledge about different model organisms and experimental approaches used in studying MPs; and to (iii) convey directions for future studies. We have summarized data from 500 studies published from January 2011 to May 2020, about different aspects of model organisms (taxonomic group of organisms, type of ecosystem they inhabit, life-stage, sex, tissue and/or organ) and experimental design (laboratory/field, ingestion/bioaccumulation/effect). We also discuss and try to encourage investigation of some less studied organisms (terrestrial and freshwater species, among groups including Annelida, Nematoda, Echinodermata, Cnidaria, Rotifera, birds, amphibians, reptiles), and aspects of MP pollution (long-term field studies, comparative studies examining life stages, sexes, laboratory and field work). We hope that the information presented in this review will serve as a good starting point and will provide useful guidelines for researchers during the process of deciding on the model organism and study designs for investigating MPs.

Effects of environmentally relevant levels of polyethylene microplastic on Mytilus galloprovincialis (Mollusca: Bivalvia): filtration rate and oxidative stress

The objective of the present study was to evaluate the potential toxic effects of polyethylene microplastics (PE-MPs) (40-48 μm) on the Mediterranean mussel Mytilus galloprovincialis in controlled laboratory conditions. The exposure was carried out for 14 days with three environmentally relevant PE-MPs concentrations of 1, 10, and 100 and a high concentration of 1000 μg/L. Effects of PE-MPs were assessed by evaluating the filtration rate (FR) after 7 and 14 days of exposure and by analyzing biochemical biomarkers of oxidative stress (catalase - CAT, glutathione S-transferase - GST, and the levels of lipid peroxidation - LPO) in the M. galloprovincialis digestive gland after 14 days of exposure. Results showed that M. galloprovincialis does not accumulate PE-MPs of 40-48 μm size in its whole tissues. The filtration rate was significantly reduced with the increase of PE-MPs concentrations. The biochemical biomarkers indicated that PE-MPs induced oxidative damage (LPO) at low concentrations (1 and 10 μg/L) with a significant reduction in females of 1000 μg/L treated group and inactivate antioxidative system (CAT and GST) in the digestive gland of both sexes at high concentrations (100 and 1000 μg/L). This study demonstrates that PE-MPs have biological effects on M. galloprovincialis at environmentally relevant concentrations thus brings new insights on the potential impacts of PE-MPs in marine bivalves.

Moringa oleifera polysaccharides regulates caecal microbiota and small intestinal metabolic profile in C57BL/6 mice

This study investigated the effects of Moringa oleifera polysaccharides (MOP) on the serum indexes, small intestinal morphology, small intestinal metabolic profile, and caecal microbiota of mice. A new type of polysaccharides with 104,031 Da molecular weight and triple helix structure was isolated from M. oleifera leaves for in vivo experiment. Forty male SPF C57BL/6 mice aged 4 weeks were average divided into four groups randomly according to the MOP gavaged daily (0, 20, 40 and 60 mg/kg body weight MOP). After a 7-day preliminary trial period and a 28-day official trial period, the mice were slaughtered. Results showed that MOP reduced glucose, total cholesterol, and malondialdehyde. It also improved superoxide dismutase and catalase in serum (P < 0.05). For small intestinal morphology, MOP improved the villi length and crypt depth in both ileum and jejunum (P < 0.05); the ratio of villi length to crypt depth in jejunum increased (P < 0.05). MOP could cause the increase of beneficial bacteria and the decrease of harmful bacteria in caecum, further affecting the function of microbiota. In addition, MOP regulated 114 metabolites enriched in the pathway related to the synthesis and metabolism of micromolecules. In sum, MOP exerted positive effects on the serum indexes and intestinal health of mice.

Copper-induced sublethal effects in Bufo gargarizans tadpoles: growth, intestinal histology and microbial alternations

Copper (Cu) is one of the environmental contaminations which can pose significant risks for organisms. The current study explores the effects of Cu exposure on the growth, intestinal histology and microbial ecology in Bufo gargarizans. The results revealed that 0.5-1 μM Cu exposure induced growth retardation (including reduction of total body length and wet weight) and intestinal histological injury (including disordered enterocyte, changes in the villi and vacuoles) of tadpoles. Also, high-throughput sequencing analysis showed that Cu exposure caused changes in richness, diversity and structure of intestinal microbiota. Moreover, the composition of intestinal microbiota was altered in tadpoles exposed to different concentrations of Cu. At the phylum level, we observed the abundance of proteobacteria was increased, while the abundance of fusobacteria was decreased in the intestinal microbiota of tadpoles exposed to 1 μM Cu. At the genus level, a reduced abundance of kluyvera and aeromonas was observed in the intestinal microbiota of tadpoles under the exposure of 0-0.5 μM Cu. Finally, functional predictions revealed that tadpoles exposed to copper may be at a higher risk of developing metabolic disorders or diseases. Above all, our results will develop a comprehensive view of the Cu exposure in amphibians and will yield a new consideration for sublethal effects of Cu on aquatic organisms.

Effects of Desiccation on Metamorphic Climax in Bombina variegata: Changes in Levels and Patterns of Oxidative Stress Parameters

Simple Summary

Global warming alters patterns of precipitation and drought, which are important factors in the survival of amphibian populations. Metamorphosis is affected by environmental changes; this is especially true of metamorphic climax, the crucial stage of amphibian development that is accompanied by significant morphological, physiological and behavioral adaptations necessary for the transition to a terrestrial habitat. This study investigated naturally occurring changes in the cellular oxidative status (antioxidant system and oxidative damage) of yellow-bellied toad larvae during this phase, and how exposure to exogenous factors such as desiccation affected them. Our results revealed clear changes in the antioxidant system’s (AOS) response and the levels of oxidative damage during metamorphic climax, with the highest response and damage observed at the end stage. Decreasing water levels during larval development altered the components of the AOS and increased oxidative damage, resulting in increased oxidative stress. The knowledge gained from this study could contribute to a better understanding of the oxidative stress that larvae experience during this critical stage of development, and the consequences of global warming—such as water loss—on amphibians.

Abstract

In this paper, we examined how the oxidative status (antioxidant system and oxidative damage) of Bombina variegata larvae changed during the metamorphic climax (Gosner stages: 42—beginning, 44—middle and 46—end) and compared the patterns and levels of oxidative stress parameters between individuals developing under constant water availability (control) and those developing under decreasing water availability (desiccation group). Our results revealed that larvae developing under decreasing water availability exhibited increased oxidative damage in the middle and end stages. This was followed by lower levels of glutathione in stages 44 and 46, as well as lower values of catalase, glutathione peroxidase, glutathione S-transferase and sulfhydryl groups in stage 46 (all in relation to control animals). Comparison between stages 42, 44 and 46 within treatments showed that individuals in the last stage demonstrated the highest intensities of lipid oxidative damage in both the control and desiccation groups. As for the parameters of the antioxidant system, control individuals displayed greater variety in response to changes induced by metamorphic climax than individuals exposed to desiccation treatment. The overall decrease in water availability during development led to increased oxidative stress and modifications in the pattern of AOS response to changes induced by metamorphic climax in larvae of B. variegata.

Effects of sodium perchlorate and exogenous L-thyroxine on growth, development and leptin signaling pathway of Bufo gargarizans tadpoles during metamorphosis

Sodium perchlorate (NaClO₄) and exogenous L-thyroxine (T4), two kinds of endocrine-disrupting chemicals (EDCs), mainly affect the circulating thyroid hormones, which regulate the initiation and rate of metamorphosis in amphibian. The aim of this study is to evaluate the potential role of EDCs in regulating the development of tadpoles and leptin signaling pathway of liver during the metamorphosis of Bufo gargarizans. There was completely opposite result of average development stage of tadpoles and morphological parameters between the NaClO₄ and T4 exposure groups. Histological analysis revealed that NaClO₄ and T4 exposure both caused liver injury, such as the decreased size of hepatocytes, atrophy of nucleus, increased melanomacrophage centres and disappearance of hepatocyte membranes. In addition, the results of RT-qPCR revealed that NaClO₄ treatment significantly inhibited the transcript levels of genes related to thyroid hormone (D2, TRα and TRβ) and leptin signaling pathway (LepR, JAK1, JAK2, and TYK2), while there was an increase of mRNA expression of these genes in the liver of tadpoles administrated with T4 compared with control. This work lays an important foundation for assessing the risk of EDCs in relation to amphibian development during metamorphosis.

Effect of Broussonetia papyrifera silage on the serum indicators, hindgut parameters and fecal bacterial community of Holstein heifers

This study investigated the effects of substitution of whole corn silage (WCS) with Broussonetia papyrifera silage (BPS) in different ratios on the serum indicators, hindgut fermentation parameters (pH, ammoniacal nitrogen, and volatile fatty acids), and fecal bacterial community of Holstein heifers. Sixteen heifers (8-month-old, 220 ± 30 kg) were randomly divided into four treatments according to different BPS substitution ratios of feed basis (0%, 25%, 50%, and 75%). The experiment consisted of a 7-day preliminary feeding period and a 30-day experimental period. On the last day of the trial, the blood samples were collected from caudal vein, and the feces samples were collected from rectum. With the increasing of BPS content, the concentration of malondialdehyde (MDA) and interleukin-1β (IL-1β) in serum decreased (P < 0.05), and the immunoglobulin A (IgA) and IL-4 content of serum increased (P < 0.05); and the hindgut pH value increased (P < 0.05). 16S rRNA sequencing found that the dominant phyla were Firmicutes, Bacteroidetes, and Verrucomicrobia; and the dominant genera were Ruminococcaceae_UCG-005, Ruminococcaceae_UCG-010, and Rikenellaceae_RC9_gut_group. Linear Discriminant Analysis Effect Size (LEfSe) analysis found 12 differential operational taxonomic units (OTUs) which have strong correlation with some serum and hindgut indicators, and have the potential to be used as biomarkers. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) found that BPS have impacts on the pathways, such as carbohydrate transport and metabolism, and promotes amino acid transport and metabolism. To sum up, inclusion of BPS in heifer diets can affect serum anti-oxidant and immune indicators, fecal parameters, composition and function of fecal microorganisms in Holstein heifers.

The effect of short-term fasting on the oxidative status of larvae of crested newt species and their hybrids

In nature, animals often face periods without food caused by seasonal fluctuations and/or prey scarcity. An organism's physiological response to imposed energetic limitations is followed by changes in mitochondrial functioning (adjustment of energy metabolism) and a reduction of non-essential processes. However, this energy-saving strategy can have its costs. In this study, we examined oxidative stress as one of the possible physiological costs of short-term, two-week-long food deprivation on developing amphibian larvae of the crested newts Triturus macedonicus and Triturus ivanbureschi and their hybrids. We investigated whether this exogenous factor additionally affected the oxidative status (fitness-related trait) of hybrid individuals. The fasting treatment led to lower growth and a lower body mass and body condition index of individuals. The results revealed that the antioxidant system (AOS) of food-deprived larvae could not cope in a proper manner with reactive oxygen species production under limited energy availability, leading to higher lipid oxidative damage. The lowest AOS response was observed for H₂O₂ scavenging parameters (catalase, glutathione peroxidase, and total glutathione), which together with the elevated activity of superoxide dismutase suggested increased H₂O₂ concentrations. Comparison between parental species and their hybrids showed that hybrid individuals suffered greater oxidative damage (as demonstrated by higher concentrations of lipid peroxides), indicating that they were more susceptible to fasting-induced oxidative stress. Overall, this study illustrates that: (i) an oxidative event is one of the costs amphibian larvae face during short-term periods of fasting, (ii) hybrids are less capable of dealing with this stressful condition, which can lower their chances of survival in a changing environment.

Biomarker and hematological fieldwork with amphibians: is it necessary to sample all night?

In the context of the global amphibian crisis, biomonitoring constitutes a valuable assessment tool to provide critical up to date information on the status and health of amphibians worldwide. The aim of the current study was to evaluate the possible confounding effects of sex, size, and time since capture on enzymatic biomarkers and hematologic parameters of the South American frog Leptodactylus latrans. Frogs were collected by hand between 9 pm and 12 am on two consecutive nights. On the first night, captured frogs were transported for 2 h by car to laboratory installations, maintained overnight in plastic containers, and blood and tissue sampled on the next morning. In contrast, frogs collected on the second night were blood and tissue sampled in the field, immediately after the capture period. Hematological parameters were analyzed, and enzymatic activities of catalase, cholinesterase (ChE), and glutathione S-transferase (GST) were determined in the plasma, liver, kidney, and muscle. A sex difference was observed only for total white blood cell counts (WBC), females exhibiting significantly greater values than males. The packed cell volume (PCV), mean corpuscular hemoglobin concentration (MCHC), WBC, and muscle ChE activity were significantly correlated with snout-vent length (SVL). The correlation was inversed in the case of MCHC, WBC, and muscle ChE, while the correlation was positive between PCV and SVL. Most examined parameters presented similar values when frogs were sampled at night following capture or the next morning. Total red blood cells (RBCs) count, and plasma enzymatic activities of ChE and GST were the only parameters that presented significantly increased values in morning samplings compared with night samplings. Overall, the current study indicates that it is best to sample the frogs as soon as possible after capture if hematologic or plasmatic biomarkers are examined. Nevertheless, it is possible to sample on the next morning if tissular biomarkers are employed.

A review of microplastics in the aquatic environmental: distribution, transport, ecotoxicology, and toxicological mechanisms

The interactions between microplastics (MPs) and aquatic organisms are becoming increasingly frequent due to the extensive distribution of MPs in aquatic environments. MPs from the aquatic environment tend to accumulate and move through living organisms. Therefore, MPs can affect human health though the food chain and human consumption. In this brief review, the environmental distribution, sources, and transport of MPs are reviewed, and the potential consequences of the presence of MPs in the aquatic environment to human food are discussed. This review also summarized the toxicity effects and toxicity mechanisms of MPs based on various environmentally relevant test species and discussed the combined toxicity effects of MPs and various pollutants in aquatic ecosystems. The knowledge of the adverse effects on combined toxicity and the mechanism of MPs toxicity are very limited. Thus, a systematic assessment of the aquatic environmental risk in various species from MPs is challenging. In the end, we identify the knowledge gaps that need to be filled and provide suggestions for future research.

Evaluation of softwood and hardwood sawmill wastes impact on the common carp "Cyprinus carpio" and its aquatic environment: An oxidative stress study

The aquatic pollution due to sawmill wood wastes constitutes a major threat to hydro-chemical and fauna characteristics of the aquatic ecosystems. When this kind of organics wastes enter aquatic environment it can be taken up by aquatic organisms through respiration and/or through their diet. This could concurrently result in oxidative stress and later having adverse effect on physiological and biochemical function. The importance of fish in the society cannot be over emphasized, hence there is the need to know the influence of sawmill wood wastes on the water quality and fish. Therefore, this work aims to study the impact of five species of wood wastes on a type of fish named common carp (Cyprinus carpio) known as the most widely cultured fish species in the world and on its aquatic environment. The monitoring of water parameters showed deterioration in water quality. The activities of superoxide dismutase (SOD), Catalase (CAT), glutathione peroxidase (GPx) and lipid peroxidation (MDA) were investigated to evaluate the degree of oxidative stress. According to t-student, there was a significant difference compared to control (P < 0.05) in the level of SOD, CAT, GPx and MDA activities in fish exposed to 5 g·l^-1 of each sawdust except for GPx, a non-significant difference (p > 0.05) was noted in the case of Beech and Dibetou. When the dispersed amount was about 0.375 g·l^-1 we noted a significant difference in the level of SOD and GPx, except for GPx a non-significant difference was detected in the case of Cedar. The level of CAT was significantly difference just in the case of Cedar and Dibetou and that of MDA was significantly difference just in the case of Beech and Mahogany. We conclude therefore that sawmill wood waste not only impact the water quality adversely but also alters the levels of different enzymes activities in Cyprinus Carpio fish by the inhibition of SOD, CAT and GPx activities and by the production of MDA, which reflects response to oxidative stress. This study provides a rational use of these enzymes as suitable biomarkers with different degrees of specificity and as important tool for environmental monitoring.

The Effect of Shelter on Oxidative Stress and Aggressive Behavior in Crested Newt Larvae (Triturus spp.)

Shelters are important for animal survival. Provision of adequate hiding places allow animals to express their natural sheltering behavior and it can have different positive effects on cortisol levels, physiological processes and mental performance. Although the absence of a refuge activates some stress response, its effect on oxidative stress has not been adequately examined. This study investigated whether the presence/absence of a shelter modifies the oxidative status (the antioxidant system and oxidative damage) and aggressive behavior of crested newt larvae (Triturus macedonicus and its hybrid with T. ivanbureschi). Our results show that individuals reared with shelters had lower values of the tested antioxidant parameters (catalase, glutathione peroxidase, glutathione S-transferase and glutathione), indicating a lower production of reactive species than individuals reared without shelter. The same pattern was observed in both T. macedonicus and its hybrid. Contrary to the activation of some physiological pathways, shelter availability did not significantly affect the rate of intraspecific aggressive behavior. The physiological benefits of shelter use can be manifested as a lower requirement for investment in the energy necessary for the maintenance of the upregulated antioxidant defenses, activation of repair systems and synthesis of endogenous antioxidants. This study highlights the importance of shelter provision, which may be valuable in habitat restoration and animal conservation studies.

Oxidative stress induction by the invasive sponge Paraleucilla magna growing on Peyssonnelia squamaria algae

The introduction of invasive species can lead to significant adverse effects on the colonized areas. The aim of the present research was to determine if the invasive behavior of Paraleucilla magna could induce the activation of the antioxidant defences in the native red algae, Peyssonnelia squamaria. Individuals of isolated P. squamaria and individuals epiphytized by P. magna, both growing on rocky bottoms, were collected. The activity of the antioxidant enzymes - catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase - and the levels of the malondialdehyde were significantly higher in the algae of the epiphytic group compared to the control group, while the detoxifying enzyme glutathione S-transferase did not show significant differences. The levels of reduced glutathione and total polyphenols were higher in the algae affected by the sponge. In conclusion, the arrival of the species P. magna induces an adaptative antioxidant response in P. squamaria determined by the use of biomarkers.

Fish response to hypoxia stress: growth, physiological, and immunological biomarkers

Water quality encompasses the water physical, biological, and chemical parameters. It generally affects the fish growth and welfare. Thus, the success of a commercial aquaculture project depends on supplying the optimum water quality for prompt fish growth at the minimum cost of resources. Although the aquaculture environment is a complicated system, depending on various water quality variables, only less of them have a critical role. One of these vital parameters is dissolved oxygen (DO) level, which requires continuous oversight in aquaculture systems. In addition, the processes of natural stream refinement require suitable DO levels in order to extend for aerobic life forms. The depletion of DO concentration (called hypoxia) in pond water causes great stress on fish where DO levels that remain below 1-2 mg/L for a few hours can adversely affect fish growth resulting in fish death. Furthermore, hypoxia has substantial effects on fish physiological and immune responses, making them more susceptible to diseases. Therefore, to avoid disease outbreak in modern aquaculture production systems where fish are intensified and more crowded, increasing attention should be taken into account on DO levels.

mRNA expression of antioxidant and biotransformation enzymes in zebrafish (Danio rerio) embryos after exposure to the tricyclic antidepressant amitriptyline

Now-a-days, the occurrence of antidepressant residues in surface waters has become a major concern. Amitriptyline (AMI) has been described to treat depression and other disorders for decades. However, little is known about its effect on non-target organisms. The aim of this study was to assess the potential impact of AMI on the mRNA expression of antioxidant and detoxification enzymes during the early embryonic development of zebrafish (Danio rerio). Fertilized D. rerio embryos were exposed to AMI at concentrations of 300 ng/L and 30 μg/L and sampled 24, 48, 96, and 144 h post fertilization (hpf) to assess the mRNA expressions of cytochrome P450 1A1, glutathione-S-transferase, glutathione peroxidase, superoxide dismutase, and catalase. The time courses of the mRNA expressions of antioxidant and detoxification enzymes revealed characteristic changes during embryonic development causing generally transient changes post hatching; however, AMI did not cause any significant impact except in the case of CAT after 144 h, which was significantly upregulated by the AMI concentration of 30 μg/L. The results suggest that the antidepressant AMI causes only moderate to minor impacts on antioxidant and detoxification enzymes during early embryonic development of the non-target organism D. rerio and that CAT is the only biomarker affected by AMI.