Stress-induced changes of plasma antioxidants in aquacultured sea bass, Dicentrarchus labrax

Testis metal toxicity remediation by agro-food waste: evidence of a protective effect of melon seed husk extract Cucumeropsis mannii silica nanoparticles on gonadotropin and sex steroid hormones

Male fertility is strongly affected by the overexpression of free radicals induced by heavy metals. The aim of this study was to produce nanoparticles from the agro-food waste, Cucumeropsis mannii melon seed husk extract (MSHE), whose burned seeds in Nigeria become incorporated into the soil contributing to pollution; and to propose a potential remediation biomarker adoptable to a metal-exposed animal model. Sol-gel precipitated melon husk silica nanoparticles were characterized by spectrophotometric and X-ray diffraction analysis. Biochemical and histopathological tests were performed on male albino rats divided into 8 groups orally exposed to Ni, Al, and Ni/Al both alone as well as co-administrated with MSHE at several dosages. Metal exposure reduced levels of plasma gonadotropin hormones follicle-stimulating hormone (FSH), Luteinizing Hormone (LH), and the sex steroid hormone testosterone, but MSHE co-administration increased them. MSHE treatment alone also raised FSH and LH levels compared to the metal-exposed groups. Plasma gonadotropin prolactin (PRL) levels were higher in each group examined, whereas MSHE co-administration significantly lowered them. Additionally, MSHE treatment alone exhibited lower PRL levels than the mixture-exposed groups and increased testosterone levels. Plasma hormonal results were confirmed by regeneration of testis architecture, testis lipid peroxidation decreases, and testis antioxidant increases. Use of agro-food waste nanoparticles has significant implications as evaluated with male albino rat plasma hormone levels. MSHE may ameliorate Ni-Al mixture-induced testicular toxicity and may be a useful future therapeutic tool.

Role of Anonychium africanum (Plantae, Fabaceae) in Metal Oxido-Inflammatory Response: Protection Evidence in Gonad of Male Albino Rat

Male fertility is strongly affected by the overexpression of free radicals induced by heavy metals. The aim of this study was to evaluate the potential antioxidant, anti-inflammatory, and gonado-protective effects of natural compounds. Biochemical and morphological assays were performed on male albino rats divided into five groups: a control group (water only), a group orally exposed to a metal mixture of Pb-Cd-Hg-As alone and three groups co-administered the metal mixture and an aqueous extract of the Nigerian medicinal plant, Anonychium africanum (Prosopis africana, PA), at three different concentrations (500, 1000, and 1500 mg/kg) for 60 days. The metal mixture induced a significant rise in testicular weight, metal bioaccumulation, oxidative stress, and pro-inflammatory and apoptotic markers, while the semen analysis indicated a lower viability and a decrease in normal sperm count, and plasma reproductive hormones showed a significant variation. Parallel phytochemical investigations showed that PA has bioactive compounds like phlobatannins, flavonoids, polyphenols, tannins, saponins, steroids, and alkaloids, which are protective against oxidative injury in neural tissues. Indeed, the presence of PA co-administered with the metal mixture mitigated the toxic metals' impact, which was determined by observing the oxido-inflammatory response via nuclear factor erythroid 2-related factor 2, thus boosting male reproductive health.

Effect of sulfate on the osmoregulatory and physio-biochemical responses of GIFT (Oreochromis niloticus) juveniles reared in potassium-deficient medium saline waters

The inland saline waters were continuously observed to have low potassium concentrations compared to their seawater counterpart of the same salinity. We hypothesize that the toxic effect of sulfate may manifest in low potassium saline (LPSW) waters compared to brackish water of the same salinity. Thus, LC50 trials were performed in GIFT (genetically improved farmed tilapia) fry (0.5 ± 0.02 g) to determine the acute sulfate toxicity in freshwater (FW, 0.5 g L-1), artificial seawater (ASW, 10 g L-1), and LPSW (10 g L-1). The median lethal concentrations (96h LC50) of sulfate ion in FW, LPSW, and ASW for the GIFT were 5.30 g L-1, 2.56 g L-1, and 2.98 g L-1, respectively. A second experiment was conducted for 21 days, exposing fish to a sub-lethal level of sulfate ion (SO42-) concentration (1000 mg L-1, one-fifth of FW LC50) with different types of waters (FW, freshwater, 0.5 g L-1; ASW, artificial seawater, 10 g L-1; LPSW, low potassium saline water, 10 g L-1) with and without sulfate inclusion to constitute the treatments as follows, (FW, FW + SO4, ASW, ASW + SO4, LPSW, LPSW + SO4). The effect of sulfate on GIFT reared in sulfate-rich potassium-deficient medium saline water was evaluated by focusing on the hematological adjustments, stress-induced oxidative damage, and osmoregulatory imbalances. The survival was not altered due to the sulfate concentration and K+ deficiency; however, there were significant changes in branchial NKA (Na+/K+-ATPase) activity and osmolality. The increase in NKA was highest in LPSW treatment, suggesting that internal ionic imbalance was triggered due to an interactive effect of sulfate and K+ deficiency. The cortisol levels showed a pronounced increase due to sulfate inclusion irrespective of K+ deficiency. The antioxidant enzymes, i.e., SOD (superoxide dismutase), catalase, GST (glutathione-S-transferase), and GPX (glutathione peroxidase), reflected a similar pattern of increment in the gills and liver of the LPSW + SO4 groups, suggesting a poor antioxidant status of the exposed group. The hepatic peroxidation status, i.e. TBARS (thiobarbituric acid reactive substances), and the peroxide values were enhanced due to both K+ deficiency and sulfate inclusion, suggesting a possible lipid peroxidation in the liver due to handling the excess sulfate anion concentration. The hematological parameters, including haemoglobin, total erythrocyte count, and hematocrit level, reduced significantly in the LPSW + SO4 group, indicating a reduced blood oxygen capacity due to the sulfate exposure and water potassium deficiency. The hepatic acetylcholine esterase activity was suppressed in all the treatments with sulfate inclusion, while the highest suppression was observed in the LPSW + SO4 group. Thus, it is concluded that sulfate-induced physiological imbalances manifest more in potassium-deficient water, indicating that environmental sulfate is more detrimental to inland saline water than freshwater or brackish water of the same salinity.

Nano Iron Versus Bulk Iron Forms as Functional Feed Additives: Growth, Body Indices, Hematological Assay, Plasma Metabolites, Immune, Anti-oxidative Ability, and Intestinal Morphometric Measurements of Nile tilapia, Oreochromis niloticus

The current study aimed to compare the utilization efficiency of iron (Fe) feed additives from either bulk or nano sources in Nile tilapia, Oreochromis niloticus diets on growth, haematological, immunity, anti-oxidative, and intestinal topography capacities. Five isonitrogenous and isoenergetic diets were performed; the basal diet served as a control with no Fe added, whereas the experimental diets were shaped by adding bulk-Fe2O3 and nano-Fe2O3 to the basal diet to preserve Fe levels at 0.2 and 0.4 mg kg-1, respectively. Results indicated that superior growth performance was recorded in fish-fed diets supplemented with 0.4 nano-Fe2O3 mg kg-1 diet. In addition, the highest (P ≤ 0.05) survival rate, absorption area of villous (AAV), mucosal to serosal amplification ratio (MSR), and villi parameters (height and width) were noticed in fish fed diet enrichment with either bulk or nano-Fe2O3 source. However, the superiority observed in nano-Fe2O3 fish groups. Also, the highest values of plasma albumin, total protein, high-density lipoprotein cholesterol (HDL-C), white blood cells (WBCs), and lymphocyte absolute count (LYM) (P ≤ 0.05) recorded in fish fed a diet supplemented with nano-Fe2O3 versus the basal diet. Moreover, the highest values of catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), and plasma lysozyme activity (P ≤ 0.05) were observed in fish fed 0.4 mg/kg-1 nano-Fe2O3, while the lowest value was recorded in fish fed the control diet. The best value of malondialdehyde activity (P ≤ 0.05) recorded in a fish-fed diet supplemented with 0.4 mg/kg-1 nano-Fe2O3. The current findings emphasize the importance of including Fe to improve fish growth, immunity, antioxidant capabilities, and intestinal structure, primarily with a nano-Fe source, which demonstrated a more effective function in satisfying Nile tilapia dietary Fe requirements and improving the aforementioned parameters.

Gut flora alterations among aquatic firefly Aquatica leii inhabiting various dissolved oxygen in fresh water

Knowledge about the impact of different dissolved oxygen (DO) on the composition and function of gut bacteria of aquatic insects is largely unknown. Herein, we constructed freshwater environments with different DOs (hypoxia: 2.50 ± 0.50, normoxia: 7.00 ± 0.50, and hyperoxia: 13.00 ± 0.50 mg/L) where aquatic firefly Aquatica leii larvae lived for three months. Their gut flora was analyzed using the combination of 16S rRNA amplicon sequencing and metagenomics. The results showed no difference in alpha diversity of the gut flora between A. leii inhabiting various DOs. However, the relative abundance of several bacterial lineages presented significant changes, such as Pseudomonas. In addition, bacterial genes with an altered relative abundance in response to various DOs were primarily related to metabolism. The alteration of these functions correlated with the DO change. This is the first to uncover structure of gut flora under various DOs in aquatic insect larvae.

Multiple exposure to thunderstorm-sound in Nile tilapia (Oreochromis niloticus): physiological response and stress recovery

The present study investigated the impacts of multiple thunderstorm-sound exposures on growth and respiratory parameters in Nile tilapia (Oreochromis niloticus) in order to evaluate the acoustic stress response. Thunderstorm-sound exposure for 3 hours triggered respiration speed with an alarm reflex and rapid elevation of opercula beat rate (OBR) and pectoral wing rate (PWR), which increased two-fold over the control with no sound treatment, and peaked (OBR, 71.33±5.86 beat/min; PWR, 75.00±3.61 beat/min) in 10 hours after initiation of sound. Thereafter, respiration rates declined over the following days and returned to near-initial levels (45.33±4.04 beat/min OBR and 43.00±1.00 beat/min PWR) by day-3, an indication that fish recovered from thunderstorm-sound stress after 3 days of exposure. However, the same reaction course was observed each time of multiple sound exposures, repeated 20 times in a row with 4 days intervals, underlining that fish could not attune to repeated thunderstorm-sound. Reduced voluntary feed intake as a result of anxiety and appetite loss was recorded in fish exposed to multiple thunderstorm-sound, resulting in 50 % less growth compared to those without sound treatment by the end of the 80 days experimentation. Therefore, it is advisable to monitor fish behavior during the 3 days stress-period after a thunderstorm event in order to prevent waste from excess feeding, that in turns may contribute environment-friendly aquaculture for the future and sustainability of the oceans.

Effects of Low Temperature on Antioxidant and Heat Shock Protein Expression Profiles and Transcriptomic Responses in Crayfish (Cherax destructor)

Low temperature is a critical factor restricting the growth and survival of aquatic animals, but research on the mechanism of response to low temperature in Cherax destructor is limited. C. destructor is one of the most important freshwater crustaceans with strong adaptability in Australia, and it has been commercialized gradually in recent years. Here, growth indicators, antioxidant parameters, anti-stress gene expression, and transcriptome sequencing were used on crayfish following 8 weeks of low-temperature acclimation. The results showed that weight gain, length gain, and molting rates decreased as the temperature decreased. The activity of antioxidant enzymes decreased, while the content of antioxidant substances and the expression of anti-stress genes increased. Transcriptome sequencing identified 589 differentially expressed genes, 279 of which were upregulated and 310 downregulated. The gene functions and pathways for endocrine disorders, glucose metabolism, antioxidant defense, and immune responses were identified. In conclusion, although low-temperature acclimation inhibited the basal metabolism and immune ability of crayfish, it also increased the antioxidant substance content and anti-stress-gene expression to protect the organism from low-temperature damage. This study provided molecular insights into the study of low-temperature responses of low-temperature-tolerant crustacean species.

Biological Effects Assessment of Antibiofouling EDCs: Gaeta Harbor (South Italy) Benthic Communities' Analysis by Biodiversity Indices and Quantitative gpx4 Expression

The most representative organisms of the Harbor of Gaeta Gulf in South Italy were analyzed for biofouling by visual census and confirmed later by molecular approach on an artificial Conatex panel dipped 3 m into a eutrophic area during the Covid-19 pandemic. Mitochondrial Cytochrome C oxidase subunit 1(COI) gene was sequenced from 20 different marine species (flora: 2 families, 2 orders; fauna: 16 families, 11 orders) to test whether the morphology-based assignment of the most common biofouling member was supported by DNA-based species identification. Twelve months of submersion resulted in generation of sufficient data to obtain a facies climax represented mainly by the bivalve mollusk, Mytilus galloprovincialis. Specific diversity and variations of the biofouling biomasses were analyzed using two different anti-biofouling paints: an endocrine disrupting chemical (EDC)-containing metal biocide, and a biocide-free paint. Also, their effects on detoxification and reproductive health of M. galloprovincialis were evaluated using glutathione S-transferase enzymatic activity and RTqPCR expression of the fertility antioxidant gene glutathione peroxidase 4 (gpx4). The obtained data provide useful indications on which future investigations may be focused and may become a potential management tool for a harbor biofouling database to assist local administrations in EDCs protection of autochthonous benthic communities and their fertility using innovative antifouling paints.

Antioxidative Defense and Fertility Rate in the Assessment of Reprotoxicity Risk Posed by Global Warming

The objective of this review is to briefly summarize the recent progress in studies done on the assessment of reprotoxicity risk posed by global warming for the foundation of strategic tool in ecosystem-based adaptation. The selected animal data analysis that was used in this paper focuses on antioxidative markers and fertility rate estimated over the period 2000-2019. We followed a phylogenetic methodology in order to report data on a panel of selected organisms that show dangerous effects. The oxidative damage studies related to temperature fluctuation occurring in biosentinels of different invertebrate and vertebrate classes show a consistently maintained physiological defense. Furthermore, the results from homeothermic and poikilothermic species in our study highlight the influence of temperature rise on reprotoxicity.

Salinity mediates the toxic effect of nano-TiO2 on the juvenile olive flounder Paralichthys olivaceus

Increased production of engineered nanoparticles has raised extensive concern about the potential toxic effects on marine organisms living in estuarine and coastal environments. Meanwhile, salinity is one of the key environmental factors that may influence the physiological activities in flatfish species inhabiting in those waters due to fluctuations caused by freshwater input or rainfall. In this study, we investigated the oxidative stress and histopathological alteration of the juvenile Paralichthys olivaceus exposed to nano-TiO₂ (1 and 10 mg L^-1) under salinities of 10 and 30 psu for 4 days. In the gills, Na⁺-K⁺-ATPase activity significantly deceased after 4 days 10 psu exposure without nano-TiO₂ compared with 1 day of acclimating the salinity from the normal salinity (30 psu) to 10 psu. Under this coastal salinity, low concentration (1 mg L^-1) of nano-TiO₂ exerted significant impacts. In the liver, the activities of superoxide dismutase, catalase, the levels of lipid peroxide and malondialdehyde increased with nano-TiO₂ exposed under 30 psu. Such increase indicated an oxidative stress response. The result of the integrated biomarker responses showed that P. olivaceus can be adversely affected by high salinity and high concentration of nano-TiO₂ for a short-term (4 days) exposure. The histological analysis revealed the accompanying severe damages for the gill filaments. Principal component analysis further showed that the oxidative stress was associated with the nano-TiO₂ effect at normal salinity. These findings indicated that nano-TiO₂ and normal salinity exert synergistic effects on juvenile P. olivaceus, and low salinity plays a protective role in its physiological state upon short-term exposure to nano-TiO₂. The mechanism of salinity mediating the toxic effects of NPs on estuarine fish should be further considered.

First record of bioaccumulation and bioconcentration of metals in Scleractinian corals and their algal symbionts from Kharg and Lark coral reefs (Persian Gulf, Iran)

Metal pollution is nowadays a serious threat worldwide for ecosystem and human health. Despite that, there is still a paucity of data on metal impact on coral reef ecosystems. Herein, the levels of eleven metals (Mn, Zn, Cu, Cr, Co, Ni, V, As, Cd, Hg, Pb) were assessed in surface sediments, seawater samples, Scleractinian corals (tissue and skeleton) and their algal symbionts collected from Kharg and Lark coral reefs in the Persian Gulf, Iran. At Kharg, surface sediments and seawater showed higher concentrations of metals than Lark, attributable to the higher metal loads and petrochemical activities in the area. Sediment quality guidelines indicated Hg as a serious threat to biota both at Kharg and Lark. Accordingly, metals bioaccumulation and bioconcentration was higher in corals from Kharg relatively to Lark Island. Interestingly, as supported by values of BCFs and BSAFs, metal accumulation was higher in coral tissues in respect to skeletons, and in zooxanthellae relatively to coral tissues at both coral reefs. Differential metal bioaccumulation was found among Scleractinian species, indicating that corals have distinct selectivity for assimilating metals from ambient sediments and seawater. Overall, metal accumulation in corals and zooxanthellae is an appropriate tool for environmental monitoring studies in coral reefs. Noteworthy, the use of Porites lutea, among Scleractinian corals, seems to be as a good bioindicator in monitoring studies of metal pollution.

Frog (Pelophylax bergeri, Günther 1986) endocrine disruption assessment: characterization and role of skin poly(ADP-ribose) polymerases

Model of the our research was the adult male amphibian anura, Pelophylax bergeri, poikilotherm species not considered threatened by the IUCN, sampled in representative sites at different degree. In the first phase, a biochemical characterization of the ADP-ribosylation on the skin of barcoded amphibian anura collected from Matese Lake (clean reference site in CE, Italy) was carried out. Two PARP isoforms were evidence: the first of 66 kDa is localized into nucleus and activated by DNA damage; the second of 150 kDa is in cytoplasm, as demonstrated by biochemical and immunohistochemical analysis. Subsequently, the PARP activity, the quantitative expression of androgen receptor gene, and the levels of arsenic and chromium in skin and testis of frog and soil, water, and sediment collected from sites at different degrees of pollution were measured. A significant variation of PARP activity and androgen receptor expression levels was detected in both tissues of barcoded frogs from Sarno and Scafati, along Sarno River (SA, Italy), suggesting that a PARP activation is correlated to pollution and to steroid-regulated physiology disruption.

Chloride and sulphate toxicity to Hydropsyche exocellata (Trichoptera, Hydropsychidae): Exploring intraspecific variation and sub-lethal endpoints

The rivers and streams of the world are becoming saltier due to human activities. In spite of the potential damage that salt pollution can cause on freshwater ecosystems, this is an issue that is currently poorly managed. Here we explored intraspecific differences in the sensitivity of freshwater fauna to two major ions (Cl(-) and SO4(2-)) using the net-spinning caddisfly Hydropsyche exocellata Dufour 1841 (Trichoptera, Hydropsychidae) as a model organism. We exposed H. exocellata to saline solutions (reaching a conductivity of 2.5mScm(-1)) with Cl(-):SO4(2-) ratios similar to those occurring in effluents coming from the meat, mining and paper industries, which release dissolved salts to rivers and streams in Spain. We used two different populations, coming from low and high conductivity streams. To assess toxicity, we measured sub-lethal endpoints: locomotion, symmetry of the food-capturing nets and oxidative stress biomarkers. According to biomarkers and net building, the population historically exposed to lower conductivities (B10) showed higher levels of stress than the population historically exposed to higher conductivities (L102). However, the differences between populations were not strong. For example, net symmetry was lower in the B10 than in the L102 only 48h after treatment was applied, and biomarkers showed a variety of responses, with no discernable pattern. Also, treatment effects were rather weak, i.e. only some endpoints, and in most cases only in the B10 population, showed a significant response to treatment. The lack of consistent differences between populations and treatments could be related to the high salt tolerance of H. exocellata, since both populations were collected from streams with relatively high conductivities. The sub-lethal effects tested in this study can offer an interesting and promising tool to monitor freshwater salinization by combining physiological and behavioural bioindicators.

Effects of hypoxia and reoxygenation on the antioxidant defense system of the locomotor muscle of the crab Neohelice granulata (Decapoda, Varunidae)

Crustaceans often occur in areas with variations in oxygen and experience situations known as hypoxia and reoxygenation. Consequences of such situations are increased levels of reactive oxygen species. To avoid oxidative damage intertidal crabs appear to possess an efficient antioxidant defense system (ADS). However, to date, studies have not addressed the strategies that are adopted by the crabs when exposed to hypoxia/reoxygenation cycles. Towards this end we evaluated the ADS and the role of melatonin as an antioxidant in the locomotor muscle of the crab Neohelice granulata under conditions of severe hypoxia and reoxygenation. Total antioxidant capacity against peroxyl radicals and the enzymes superoxide dismutase, catalase, glutathione peroxidase (GPx), and glutathione-S-transferase as well as the key enzyme of glutathione synthesis, glutamate cysteine ligase (GCL), were evaluated. Furthermore, GSH, GSH/GSSG index as well as hemolymph and cellular melatonin levels were evaluated. During hypoxia, increased GPx and GCL activity and decreased GSH and mitochondrial melatonin levels were observed, but during reoxygenation catalase activity increased and cytosolic melatonin levels decreased. It appears that the ADS in the locomotor muscle of N. granulata exert a modulating effect when being confronted with hypoxia and reoxygenation to avoid oxidative stress. During hypoxia, the ADS appear to target GPX activity as well as GSH and mitochondrial melatonin. During reoxygenation, however, evidence suggests that catalase and cytosolic melatonin are involved in the recovery of the locomotor muscle from oxidative damage and the suppression of further damage.

High environmental ammonia elicits differential oxidative stress and antioxidant responses in five different organs of a model estuarine teleost (Dicentrarchus labrax)

We investigated oxidative status and antioxidant profile in five tissues (brain, liver, gills, muscle and kidney) of European sea bass (Dicentrarchus labrax) when exposed to high environmental ammonia (HEA, 20 mg/L~1.18 mM as NH4HCO3) for 12 h, 2 days, 3.5 days, 7.5 days and 10 days. Results show that HEA triggered ammonia accumulation and induced oxidative stress in all tissues. Unlike other organs, hydrogen peroxide (H2O2) and malondialdehyde (MDA) accumulation in liver were restored to control levels. This recovery was associated with a concomitant augmentation in superoxide dismutase (SOD), catalase (CAT), components of glutathione redox cycle (glutathione peroxidase GPX, glutathione reductase, reduced glutathione), ascorbate peroxidase activity and reduced ascorbate content. On the contrary, in brain during prolonged exposure many of these anti-oxidant enzymes were either unaffected or inhibited, which resulted in persistent over-accumulation of H2O2 and MDA. Branchial and renal tissue both involved in osmo-regulation, revealed an entirely dissimilar compensatory response; the former rely mainly on the ascorbate dependent defensive system while the glutathione catalytic pathway was activated in the latter. In muscle, GPX activity first rose (3.5 days) followed by a subsequent drop, counterbalanced by simultaneous increment of CAT. HEA resulted in a relatively mild oxidative stress in the muscle and kidney, probably explaining the modest anti-oxidative responses. Our findings exemplify that oxidative stress as well as antioxidant potential are qualitatively diverse amongst different tissues, thereby demonstrating that for biomonitoring studies the screening of adaptive responses at organ level should be preferred over whole body response.

Identification and analysis of genome-wide SNPs provide insight into signatures of selection and domestication in channel catfish (Ictalurus punctatus)

Domestication and selection for important performance traits can impact the genome, which is most often reflected by reduced heterozygosity in and surrounding genes related to traits affected by selection. In this study, analysis of the genomic impact caused by domestication and artificial selection was conducted by investigating the signatures of selection using single nucleotide polymorphisms (SNPs) in channel catfish (Ictalurus punctatus). A total of 8.4 million candidate SNPs were identified by using next generation sequencing. On average, the channel catfish genome harbors one SNP per 116 bp. Approximately 6.6 million, 5.3 million, 4.9 million, 7.1 million and 6.7 million SNPs were detected in the Marion, Thompson, USDA103, Hatchery strain, and wild population, respectively. The allele frequencies of 407,861 SNPs differed significantly between the domestic and wild populations. With these SNPs, 23 genomic regions with putative selective sweeps were identified that included 11 genes. Although the function for the majority of the genes remain unknown in catfish, several genes with known function related to aquaculture performance traits were included in the regions with selective sweeps. These included hypoxia-inducible factor 1β· HIFιβ ¨ and the transporter gene ATP-binding cassette sub-family B member 5 (ABCB5). HIF1β· is important for response to hypoxia and tolerance to low oxygen levels is a critical aquaculture trait. The large numbers of SNPs identified from this study are valuable for the development of high-density SNP arrays for genetic and genomic studies of performance traits in catfish.

Anti-oxidative defences are modulated differentially in three freshwater teleosts in response to ammonia-induced oxidative stress

Oxidative stress and the antioxidant response induced by high environmental ammonia (HEA) were investigated in the liver and gills of three freshwater teleosts differing in their sensitivities to ammonia. The highly ammonia-sensitive salmonid Oncorhynchus mykiss (rainbow trout), the less ammonia sensitive cyprinid Cyprinus carpio (common carp) and the highly ammonia-resistant cyprinid Carassius auratus (goldfish) were exposed to 1 mM ammonia (as NH₄HCO₃) for 0 h (control), 3 h, 12 h, 24 h, 48 h, 84 h and 180 h. Results show that HEA exposure increased ammonia accumulation significantly in the liver of all the three fish species from 24 h–48 h onwards which was associated with an increment in oxidative stress, evidenced by elevation of xanthine oxidase activity and levels of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA). Unlike in trout, H₂O₂ and MDA accumulation in carp and goldfish liver was restored to control levels (84 h–180 h); which was accompanied by a concomitant increase in superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase activity and reduced ascorbate content. Many of these defence parameters remained unaffected in trout liver, while components of the glutathione redox cycle (reduced glutathione, glutathione peroxidase and glutathione reductase) enhanced to a greater extent. The present findings suggest that trout rely mainly on glutathione dependent defensive mechanism while carp utilize SOD, CAT and ascorbate as anti-oxidative sentinels. Hepatic cells of goldfish appear to utilize each of these protective systems, and showed more effective anti-oxidative compensatory responses towards HEA than carp, while trout were least effective. The present work also indicates that HEA exposure resulted in a relatively mild oxidative stress in the gills of all three species. This probably explains the almost complete lack of anti-oxidative responses in branchial tissue. This research suggests that oxidative stress, as well as the antioxidant potential clearly differ between salmonid and cyprinid species.

Hematologic, plasma biochemistry, and select nutrient values in captive smooth dogfish (Mustelus canis)

The Indianapolis Zoo maintains a large collection of smooth dogfish (Mustelus canis). During the first several years of captivity, there was a period of high mortality in adult, wild-caught sharks in the collection. Smooth dogfish with superficial abrasions would rapidly succumb to infection and death, regardless of the treatment approach. Although the sharks did successfully produce viable offspring, there was an elevated pup mortality rate, with 0% of the pups reaching 1 yr of age during the same period of high mortality in adult sharks. This poor response to captivity prompted interest in the physiologic response of these animals to illness. The objective of this investigation was to establish a preliminary data set of hematologic and plasma chemistry reference intervals, along with select nutrient parameters specific to wild-caught adults maintained in prolonged captivity (i.e., greater than 22 mo). Blood samples were collected from 20 clinically healthy, male (n = 10) and female (n = 10) dogfish sharks at the Oceans facility at the Indianapolis Zoo. Although gender differences in mortality rate were not apparent, complete blood cell counts, plasma biochemical profiles, and select nutrient analyses were performed and analyzed accordingly. Statistically significant differences (P < or = 0.05) specific to sex were determined for parameters including packed cell volume (PCV), absolute and relative fine eosinophilic granulocytes, relative percentage of coarse eosinophilic granulocytes, globulins, the albumin/globulin ratio, total protein, phosphorus, iron, selenium and copper. White blood cell counts appear to be lower in this species compared to other captive elasmobranchs. Further research into appropriate hematology standards including nutritional parameters appears warranted.

Spatio-temporal variation in territory quality and oxidative status: a natural experiment in the Seychelles warbler (Acrocephalus sechellensis)

1. Fluctuations in the quality of the habitat in which an animal lives can have major consequences for its behaviour and physiological state. In poor-quality habitat with low food availability, metabolically intensive foraging activity is likely to result in increased generation of reactive oxygen species, while scarcity of food can lead to a weakening of exogenously derived antioxidant defences. The consequent oxidant/antioxidant imbalance may lead to elevated oxidative stress. 2. Although the link between food availability and oxidative stress has been studied in the laboratory, very little is known about this relationship in the wild. Here, we investigate the association between territory quality (measured through food availability) and oxidative stress in the Seychelles warbler (Acrocephalus sechellensis). 3. Seychelles warblers are insectivorous birds that inhabit a fixed feeding territory year round. Individuals experience profound and rapid local fluctuations in territory quality within these territories, owing to changing patterns of vegetation defoliation resulting from seasonal changes in prevailing wind direction and wind-borne salt spray. 4. As expected, oxidant generation (measured as reactive oxygen metabolites; ROMs) was higher when territory quality was low, but there was no correlation between territory quality and antioxidant capacity (OXY). The negative correlation between territory quality and ROMs was significant between individuals and approached significance within individuals, indicating that the pattern resulted from individual responses to environmental variation. 5. ROMs and OXY levels within individuals were positively correlated, but the relationship between territory quality and ROMs persisted after including OXY as a covariate, implying that oxidative stress occurs in low territory quality conditions. 6. Our results indicate that the oxidative stress balance of an individual is sensitive to relatively short-term changes in territory quality, which may have consequences for the birds' fitness.

Dietary lipid level induced antioxidant response in Manchurian trout, Brachymystax lenok (Pallas) larvae

This study was designed to determine the nutritional lipid requirement of Manchurian trout and to investigate the effects of lipid concentrations on the antioxidant status in larvae with experimental diets with different lipid levels. Oxidative stress differences between different organs and tissues were also assessed. Manchurian trout larvae were fed for 35 days and, during that period, growth and survival, the activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) and content of malondialdehyde (MDA) in viscera, muscle, gill and brain of four diets, lipid levels from 15 to 30%, and control treatment were measured. Growth rates were similar, but survival was low, between high and low dietary lipid levels. SOD activity was stimulated in viscera, muscle and brain in high lipid diets, but reduced in gills with increased lipid content. SOD was kept lower in the control group. GPX activity was inhibited in viscera and stimulated in gill, muscle and brain. CAT activities were enhanced by all treatments and showed the lowest values in the control. Lipid peroxidation of the diet was promoted in all organs, excluding the gill which showed no regular pattern. MDA content increased with increased dietary lipid levels in viscera, muscle and brain. Our results indicate that the most appropriate lipid requirement is probably 20-25% and a higher dietary level of lipids might induce oxidative stress in Manchurian trout larvae. The brain and gill were probably the most sensitive organs to oxidative damage.

Ex vivo inhibitory effect on tilapia LDL oxidation and hypolipidemia properties of Glycine tomentella root extract

The ethanolic extract of I-Tiao Gung (GT-E) (Glycine tomentella root extract) was found to reduce the oxidative rate and prolonged lag phase of LDL in human (Homo sapiens) and tilapia (Oreochromis mossambicus). The in vivo effect of GT-E was determined using tilapia as a model. Hyperlipidemia and hypercholesterolemia were induced in fish by feeding commercial feed daily at 2% body mass for 8 weeks, or at 1% body mass for 12 weeks. Thirty two adult male tilapia were randomly divided into two groups and fed with feed containing 1% (w/w) GT-E or control diet for 12 weeks. Specific growth rate was similar between the GT-E group and the control group. Total triacylglycerol, total cholesterol and low-density lipoprotein cholesterol (LDL-C) in plasma of the GT-E group were significantly lower, while plasma total antioxidant status was significantly higher than those of the control group. GT-E fed fish had longer lag phase of Cu2+-induced LDL oxidation and retained more alpha-tocopherol in LDL particles than the control fish. LDL from the GT-E group had more monounsaturated fatty acids and less polyunsaturated fatty acids than the control group indicative of its effect on fatty acids metabolism. GT-E demonstrated hypolipidemic and hypocholesterolemic effects and inhibiting LDL oxidation in tilapia similar to the effects in mammals, thus tilapia can serve as a surrogate animal model for prescreening anti-atherosclerosis effect of natural products.

Effects of melatonin administration on oxidative stress and daily locomotor activity patterns in goldfish

Melatonin has a number of physiological functions in addition to light-dark transduction. In recent years, many in vivo and in vitro studies in rodents have revealed an important antioxidant activity of melatonin, both directly and indirectly. Nevertheless, the potential effects of melatonin as an antioxidant in fish remain unknown. The aim of this research was to evaluate the capacity of melatonin injections (3 mg/kg) to attenuate oxidative damage after submitting goldfish to oxidative stress caused directly by hydrogen peroxide (H2O2) baths and indirectly by hypoxia and subsequent reoxygenation, as well as the locomotor activity. The results revealed that melatonin decreased lipid damage in muscle after hypoxia/reoxygenation (1.22 vs. 2.27 nmoles lipid peroxides/g tissue), but not in liver. Mortality caused by oxidative stress was not attenuated by melatonin. Surprisingly, melatonin caused an increase of mortality (50 vs. 95%) when administered before hypoxia. Locomotor activity was also affected by melatonin but not by the administration of the vehicle, suggesting a sedative effect of melatonin in goldfish. In conclusion, melatonin administration provoked slight effects on lipid peroxidation and mortality resulting from oxidative stress, with reduction of locomotor activity in relation to the vehicle.

Effect of alpha-tocopherol on antioxidant enzyme activities and lipid peroxidation in rainbow trout (Oncorhynchus mykiss)

In this study, the effect of alpha-tocopherol on the antioxidant capacity of rainbow trout (Oncorhynchus mykiss) was determined. For this purpose, activities of antioxidant enzymes such as catalase (CAT), peroxidase (POD) and glutathione reductase (GSSG-Rx) were investigated. Enzyme activities were measured at 0 (control), 1, 3 and 5 h after alpha-tocopherol injection. In addition, the levels of malondialdehyde (MDA) as a lipid peroxidation marker were determined in the erythrocytes. The results showed that alpha-tocopherol significantly activated the CAT, POD and GSSG-Rx enzymes as compared with the enzyme activities found in the controls (p < 0.05). However, MDA levels were significantly decreased by alpha-tocopherol treatment (p < 0.05). The results suggest that alpha-tocopherol may have a pro-oxidant tendency at a high dose and cause mild oxidative stress which could modulate signal transduction cascades, redirect gene expression, and influence many cellular responses such as proliferation, differentiation, and reproduction. For this reason, alpha-tocopherol should be used carefully in all applications in relation to fish.

Waterborne and dietary hexavalent chromium exposure causes DNA-protein crosslink (DPX) formation in erythrocytes of largemouth bass (Micropterus salmoides)

Formation of DNA-protein crosslinks (DPXs) was demonstrated in erythrocytes from fathead minnows (Pimephales promelas) and largemouth bass (Micropterus salmoides) exposed to hexavalent chromium [Cr(VI)], a known carcinogenic and mutagenic metal contaminant of many industrial waterways. Tank water exposure of 2-3 in. fathead minnows to 2 ppm Cr(VI) led to significant DPX formation in erythrocytes, with over 140-200% elevations above background levels at 3-4 days, respectively. Largemouth bass exposed similarly were found to have 62% elevation of DPX levels after 4 days. When largemouth bass were fed a diet of minnows injected with 20 microg Cr(VI) for 5 days, a significant (p<0.01) increase of DPXs in erythrocytes was observed, with 80% elevation above erythrocytes from bass fed minnows injected only with saline. However, when largemouth bass were fed a diet exclusively of minnows exposed to 2 ppm Cr(VI) for 21 days, there was no significant difference in DPX levels compared to bass fed control (unexposed) minnows. This study provides evidence that DPX formation occurs in erythrocytes of fathead minnows exposed under controlled conditions to low ppm Cr(VI) concentrations, which is at or below concentrations previously assigned no observable effect levels. Furthermore, it appears that both waterborne and high dose dietary exposure to Cr(VI) can lead to DPX formation in erythrocytes of predatory fish species such as bass. However, it is unlikely that a bioconcentration of chromium in the food chain would be a major concern at these low ppm levels of exposure. Further, it may be difficult to achieve dietary Cr(VI) levels high enough to elicit DPXs in predatory fish under most environmental exposure scenarios.

Trace metal concentration, antioxidant enzyme activities and susceptibility to oxidative stress in the tricoptera larvae Hydropsyche exocellata from the Llobregat river basin (NE Spain)

Caddisfly larvae of Hydropsyche exocellata were sampled from seven locations receiving increasing levels of urban and industrial waste water discharges along the Llobregat river system (NE Spain) during spring and summer 2003. Locations were selected to include aquatic communities in poor and good ecological state according to measured physicochemical water parameters and the analysis of benthic macroinvertebtrate communities. Whole body residues of selected metals (Fe, Al, Zn, Cu, Co, Ni, Pb, Cd) were determined in conjunction with antioxidant enzyme activities (superoxide dismutase, SOD; catalase, CAT; glutathione peroxidase activity of GST, GSTPX), a phase II enzyme (glutathione-S-transferase, GST) and lipid peroxide levels measured as thiobarbituric reactive species (TBARs) with the aim of investigating whether resident macroinvertebrate benthic species were responsive to changes in water quality. Caddisfly larvae inhabiting those rivers were exposed to increasing levels of metal pollution. Enhanced activities of two (CAT and GST) out of the four tested enzymes, coupled with increased levels of TBARs, indicated increasing levels of stress in the studied species towards downstream reaches or locations near industrial and urban areas. These results indicate that combination of chemical and biochemical responses can be used to assess and diagnose pollution in high stressed river ecosystems.

Vitamin E in early stages of sea bass (Dicentrarchus labrax) development

This study reports titration of vitamin E levels in the sea bass (Dicentrarchus labrax) using high-pressure liquid chromatography. The first part of the work is devoted to vitamin E detection in: (1) plasma of maturing females and males characterized by different body sizes; (2) seminal fluid and eggs; and (3) developing embryos of sea bass fed with vitamin E. In the second part of the study, variations of vitamin E levels during larval development are analyzed. The results show a direct correlation between plasma vitamin E content and body size for both adult male and female sea bass. High vitamin E levels were found in seminal fluid, in eggs before and after fertilization, and in embryos during development and at hatching, whereas vitamin E level was low in dead embryos and in embryos with limited survival. During larval development, the vitamin E content decreased slowly but steadily during the first four days of larval growth; subsequently, it progressively increased from day 9 to day 40. In teratogenic larvae, vitamin E content was significantly higher than in normal larvae. This study provides evidence on how vitamin E exerts an antioxidant defense in sea bass reproduction.

Sublethal ammonia and urea concentrations inhibit rainbow trout (Oncorhynchus mykiss) erythrocyte glucose-6-phosphate dehydrogenase

In vitro and in vivo effects of sublethal ammonia and urea concentrations were assayed on glucose-6-phosphate dehydrogenase (G6PD) of rainbow trout (Oncorhynchus mykiss) erythrocyte. G6PD was purified from erythrocytes with a specific activity of 16.7 EU (mmol NADP+/min)/mg protein and approximately 1600-fold in a yield of approximately 60% by ammonium sulphate precipitation and 2',5'-ADP Sepharose 4B affinity chromatography. The purity of the enzyme was confirmed using SDS polyacrylamide gel electrophoresis. Experiments with ammonia (2.2-5.5 microM) and urea (20-50 microM) showed the inhibitory effects on the enzyme, in vitro. Inhibition effects were determined in vitro by Lineweaver-Burk and regression graphs. The dissociation constant of the enzyme inhibitor complex (Ki) and 50% inhibitory values were 2.26+/-1.21 and 2.86+/-3.51 microM for ammonia and 18.69+/-6.75 and 23.77+/-4.58 microM for urea, respectively. In vivo studies in rainbow trout erythrocytes showed significant (p < 0.01) inhibition of G6PD by ammonia and urea. However, ammonia inhibited more than urea since there were significant differences between the final values of erythrocyte G6PD activities.

Antioxidant defense of rainbow trout (Oncorhynchus mykiss) in relation to dietary n-3 highly unsaturated fatty acids and vitamin E contents

This study examined the modulation of the antioxidant status and related physiological changes in rainbow trout Oncorhynchus mykiss under different levels of dietary n-3 highly unsaturated fatty acids (n-3 HUFA) and vitamin E. Six diets containing 0, 100 or 1000 mg alpha-tocopheryl acetate kg(-1) diet and 20% or 48% n-3 HUFA provided by normal fish oil or DHA concentrated fish oil, respectively, were fed to 100 g size fish for 15 weeks. Growth of fish fed vitamin E deficient diets under both levels of n-3 HUFA were slightly retarded, accompanied by a reduction of hematocrit values, an enlargement of liver and spleen, an elevation of lipid hydroperoxide in red blood cell and the antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase). Supplementation of vitamin E could protect the fish from these adverse effects; however the higher dose was no better compared to the moderate dose. The modulations were clearly seen in fish fed high n-3 HUFA (48%) since they were under greater oxidative stress as indicated by the markers, lipid hydroperoxide and 8-isoprostane. The increased activity of enzymes corresponds to physiological mechanisms combating the elevation of free radicals under oxidative stress and a dietary fatty acid profile-dependent moderate dose of vitamin E is all that is required to function as an effective antioxidant.