Paralichthys Orbignyanus Research Articles

Seasonal seminal quality variations and vitrification prospects in black flounder Paralichthys orbignyanus

Long-term preservation of gametes has been identified as a tool to improve broodstock management and increase the number of juveniles produced by artificial fertilization. Paralichthys orbignyanus is an important commercial and recreational species distributed in marine and estuarine waters from Rio de Janeiro (Brazil) to the San Matías Gulf (Argentina). This work focused on studying the seminal quality of tank-reared P. orbignyanus, demonstrating that males are fluent year-round, with the highest yields at the early reproductive season. Fresh sperm exhibited good forward swimming, and samples could be refrigerated up to 48 h while retaining their motility after activation. The optimal conditions for P. orbignyanus sperm motility activation were established as 950 mOsmol/Kg and pH values between 7 and 7.9. Additionally, a well-defined protocol for semen vitrification was developed to assess the cryotolerance of this species’ sperm. We successfully produced high-quality sperm samples, using two vitrification formulations containing trehalose and both z-1000 and x-1000 polymers, that can be used in a near-future in vitro embryo production program.

Genome sequencing and analysis of black flounder (Paralichthys orbignyanus) reveals new insights into Pleuronectiformes genomic size and structure

Black flounder (Paralichthys orbignyanus, Pleuronectiformes) is a commercially significant marine fish with promising aquaculture potential in Argentina. Despite extensive studies on Black flounder aquaculture, its limited genetic information available hampers the crucial role genetics plays in the development of this activity. In this study, we first employed Illumina sequencing technology to sequence the entire genome of Black flounder. Utilizing two independent libraries—one from a female and another from a male—with 150 bp paired-end reads, a mean insert length of 350 bp, and over 35 X-fold coverage, we achieved assemblies resulting in a genome size of ~ 538 Mbp. Analysis of the assemblies revealed that more than 98% of the core genes were present, with more than 78% of them having more than 50% coverage. This indicates a somehow complete and accurate genome at the coding sequence level. This genome contains 25,231 protein-coding genes, 445 tRNAs, 3 rRNAs, and more than 1,500 non-coding RNAs of other types. Black flounder, along with pufferfishes, seahorses, pipefishes, and anabantid fish, displays a smaller genome compared to most other teleost groups. In vertebrates, the number of transposable elements (TEs) is often correlated with genome size. However, it remains unclear whether the sizes of introns and exons also play a role in determining genome size. Hence, to elucidate the potential factors contributing to this reduced genome size, we conducted a comparative genomic analysis between Black flounder and other teleost orders to determine if the small genomic size could be explained by repetitive elements or gene features, including the whole genome genes and introns sizes. We show that the smaller genome size of flounders can be attributed to several factors, including changes in the number of repetitive elements, and decreased gene size, particularly due to lower amount of very large and small introns. Thus, these components appear to be involved in the genome reduction in Black flounder. Despite these insights, the full implications and potential benefits of genome reduction in Black flounder for reproduction and aquaculture remain incompletely understood, necessitating further research.

Effect of salinity on fads2 and elovl gene expression and fatty acid profile of the euryhaline flatfish Paralichthys orbignyanus

Paralichthys orbignyanus, a commercially important flatfish, presents in its natural environment, significant variations in salinity and fatty acid composition of its diet. In this work, we aimed to study the impact of salinity on the genetic expression of fads2 and elovl and its reflection in the muscle fatty acid profile of the fish. Since genetic resources for this species are absent, we performed hepatic transcriptome sequencing (mRNA-Seq) and conducted de novo assembly to obtain the novel transcripts of fads2 and elovl. The sequences obtained were used to analyze possible changes in the genetic expression of these enzymes in juvenile P. orbignyanus when cultured at four salinities (2, 10, 18 and 26 ppt) fed on a diet rich in 18:3n-3 and 18:2n-6 but poor in LC-PUFA. Results showed that salinity has a significant modulatory effect on fads2 gene expression, with an increase at 2 ppt salinity. Total lipid content in fish muscle decreased when moving away from the isosmotic point (10.9 ppt) suggesting higher energetic demands at 2, 18 and 26 ppt. This effect was also evident for specific fatty acids, such as 16:1n-7, 16:2n-3, 18:4n-3, 20:1n-9, 20:4n-3 and 20:5n-3. Interestingly, some fatty acids, particularly total MUFA, 18:2n-6 and 22:6n-3 presented a dichotomous profile between lower and higher salinities, suggesting the adaptation of P. orbignyanus to different environmental salinities. This study highlights the remarkable ability of P. orbignyanus to adapt to a wide range of salinities demonstrating the strong euryhalinity of this species. The observed salinity effects hold potential significance for its application in aquaculture.

Differential modulation of digestive enzymes and energy reserves at different times after feeding in juveniles of the marine estuarine-dependent flatfish Paralichthys orbignyanus (Valenciennes, 1839).

Integrative studies are lacking on the responses of digestive enzymes and energy reserves in conjunction with morphological traits at distinct postprandial times in marine estuarine-dependent flatfishes of ecological and economic importance, such as Paralichthys orbignyanus. We determined total weight (TW), hepato-somatic index (IH), activities of digestive enzymes in the intestine, and the concentration of energy reserves in the liver and the muscle at 0, 24, 72, and 360 h after feeding in juveniles of P. orbignyanus. Amylase activity decreased at 72 h (about 30%). Maltase, sucrose, and lipase activities reached peak at 24 h (67%, 600%, and 35%, respectively). Trypsin and aminopeptidase-N activities at 24 and 72 h, respectively, were lower than those at t = 0 (53% and 30%). A peak increase in the concentration of glycogen and triglycerides in the liver (24 h) (86% and 89%, respectively) occurred. In muscle, glycogen and triglyceride concentrations were unchanged at 24 h and higher at 72 and 360 h (100% and 60%). No changes were found in TW, IH, free glucose in the liver and muscle, and protein in the liver. The protein concentration in the muscle sharply increased at 24 and 360 h after feeding (60%). The results indicate a distinct and specific response of central components of carbohydrate, lipid, and protein metabolism that could be adjustments at the biochemical level upon periods of irregular feeding and even of long-term food deprivation inside coastal lagoons or estuaries. The distinct responses of digestive enzymes in the intestine and energy reserves in the liver and muscle suggest the differential modulation of tissue-specific anabolic and catabolic pathways that would allow the maintenance of physical conditions.

Integrating the local knowledge of fishers into an ecological model for the sustainable management of a protected coastal lagoon area in Uruguay

Abstract This study uses the local knowledge of artisanal fishers to assess ecosystem structure, functioning, and fishing impacts within a coastal lagoon in Uruguay. To this end, we used an Ecopath with Ecosim modelling approach based on fishers’ knowledge and scientific data. The model considered 23 functional groups, while three fleets represented fishing activities targeting different species. The model output shows a foodweb which spans four trophic levels, including fish species as top predators, such as the flatfish Paralichthys orbignyanus and the tararira Hoplias malabaricus. Furthermore, according to fishers’ knowledge, gastropods, polychaetes, and bivalves constitute primary consumers, while detritus and phytoplankton represent the primary food sources. The trophic impact analysis shows that the fish Mugil spp. and Odontesthes spp. generate important positive and negative impacts on most other ecosystem components, while fishing impacts occur at moderate exploitation levels on the targeted fish species. The indicators of the ecosystem effects of fishing including The Trophic Level of the Catch ranging from 2.4 to 2.6, the Primary Production Required showing relative low values of 2.3% and low probability of an ecosystem being sustainably fished alert us to the risk of ecosystem-level overfishing. The vast potential of fishers’ knowledge in research can allow the co-creation of new insights into ecosystem structure and function. By including fishers in research, local communities can be empowered and benefit from management decisions through their trust in science.

Population structure of mud flounder Paralichthys orbignyanus from the south-western Atlantic Ocean.

The mud flounder Paralichthys orbignyanus (Pleuronectiformes, Paralichthyidae) inhabits shallow waters of low salinities and mud bottoms in the temperate marine coastal regions of the Bonaerensean Ecoregion of the Argentinean Biogeographic Province in the south-western Atlantic Ocean. Specimens of P. orbignyanus were collected from Lagoa dos Patos (LDP) (southern Brazil), Mar Chiquita (MCH) and Marisol (MAR) both located in Buenos Aires (Argentina), and San Antonio Oeste (SAO) in the San Matías Gulf, Rio Negro (Argentina). A fragment of the mitochondrial DNA of the Control Region and seven microsatellite loci were characterized. In the Control Region, P. orbignyanus showed high variability, low nucleotide diversity, mild population expansion and a coalescence time of 35,000 years before the present. Flounders provided evidence of a genetic structure between the sampling sites LDP, MCH, MAR vs. SAO. On the other hand, P. orbignyanus displayed a lower to moderate contemporary genetic structure among all samples except between LDP and MCH. With no evidence of isolation by distance, this analysis supports a model of limited gene flow that is likely to be associated with a consistent larvae retention in all sampling sites. In addition, the present connectivity is ascribed to a lower migration process from SAO in the San Matías Gulf congruent with the prevailing littoral drift.

Age and growth of the red flounder Paralichthys orbignyanus (Teleostei: Pleuronectiformes) in southern Brazil

The red flounder Paralichthys orbignyanus is a large pleuronectiform fish endemic in coastal waters, coastal lagoons and estuaries in the southwestern Atlantic. Although less abundant than other Paralichthys spp, its high price makes it a valuable resource for small-scale fishers that have been intensely fished in the last decades. To study its growth and lifespan in southern Brazil, we examined thin otolith sections collected for age determinations of both young-of-the-year (YOY) and older fishes. Opaque bands form mainly in spring and summer, coincident with the reproductive season. Larger and older males reached 601 mm and eight years, while females reached 985 mm and 11 years. The assumed daily microincrements counts ranged from 127 to 196 for YOY of 135 to 184 mm TL. The common weight-length equation for grouped sexes was TW♀♂=0.000015TL2.93 (mm, g). The von Bertalanffy growth equations were: TL♀=1076(1–e–0.15 (t+0.78)); TL♂=652(1–e–0.28 (t+0.48)); and TL♀♂=839(1–e–0.20 (t+0.67)). Therefore, P. orbignyanus is a fast-growing and relatively short-living species for which females attain larger length and older ages than males, characteristics that have to be taken into account for its stock assessment and management.

Acute toxicity and sublethal effects of nitrite on oxidative stress in early juvenile Brazilian flounder, Paralichthys orbignyanus

This study evaluated the acute toxicity and sublethal effects of nitrite on oxidative stress parameters in early juvenile Brazilian flounder, Paralichthys orbignyanus. Fish were exposed to six concentrations of nitrite: 20, 40, 80, 170, 330 and 550 mg NO2−N-L−1, plus a control with no added nitrite, all in triplicate for 96 h. Every 24 h, the tanks were monitored to check possible mortality to estimate the LC50. At the end of the experiment, fish were sampled for stress oxidative analysis. All fish exposed to 550 mg NO2−N-L−1 died within the first 24 h. The LC50 ranged from 427.8 to 393.1 mg NO2−N-L−1 for 24 and 96 h respectively. The total antioxidant capacity against peroxyl radicals (ACAP) showed a gradual reduction in fish exposed to nitrite levels from 170 mg NO2−N-L−1. The glutathione S-transferase (GST) activity was higher in 80, 170 and 330 mg NO2−N-L−1. The non-proteic (NPSH) and proteic (PSH) thiols levels were higher in 170 and 330 mg NO2−N-L−1 compared with the control, 20 and 40 mg NO2−N-L−1. Lipid peroxidation (LPO), as indicated by the thiobarbituric acid reactive substances (TBARS) level, was significantly higher in fish exposed to 330 mg NO2−N-L−1 than the control and 20 mg NO2−N-L−1. Moreover, a pro-oxidant condition was induced when P. orbignyanus were exposed to concentrations from 80 mg NO2−N-L−1, which was evidenced by alterations in the antioxidant system and increased levels of LPO. Therefore, it is recommended that the nitrite concentration do not exceed 40 mg NO2−N-L−1 in order to avoid oxidative stress for early juvenile Brazilian flounder.

Lymphocystic Disease in Wild Croaker (Micropogonias furnieri) and Flounder (Paralichthys orbignyanus)

Lymphocystis disease has been reported worldwide in several species of freshwater fish and marine fish, naturally infected in the wild environment, or in intensive crops in farms. Nodular warty lesions of irregular surface were observed in the tegument and fins and mouth in a species of croaker (Micropogonias furnieri) caught in Cassino beach Rio Grande RS, Brazil and flounder (Paralichthys orbignyanus) caught in the city of San Clemente, Argentina. The skin lesions fragments were fixed in 20% buffered formalin, and the histological sections were stained with hematoxylin and eosin and Periodic Acid-Schiff (PAS), where microscopic alterations were visualized in the form of hyaline capsule with small basophilic structures in nodules and fibroblastic cells proliferation. The reported cases were based on the disease macroscopic findings characteristic of a lymphocystis disease, along with the histopathology, which confirmed the presence of the disease in the analyzed tissues.

Ability of Vibrio vulnificus isolated from fish of the Lagoa dos Patos estuary in south Brazil to form biofilms after sublethal stress and bacterial resistance to antibiotics and sanitizers

The present study aimed to investigate the presence of Vibrio vulnificus in fish captured at the Lagoa dos Patos estuary (RS, Brazil), to establish a correlation between bacterial biofilm formation and sublethal stress, and to assess the resistance of the isolates to antimicrobials and sanitizers. A total of 217 isolates characteristic of Vibrio sp. were analyzed. Isolates were identified and subsequently their ability to form biofilm, the impact of exposure to sublethal stress on their biofilm formation ability, and their resistance to antimicrobial and to sodium hypochlorite and chlorine dioxide sanitizers were evaluated. V. vulnificus was isolated from the fish Paralichthys orbignyanus and Micropogonias furnieri. The bacterial isolates examined were able to form biofilms. Biofilm formation ability of these strains was decreased or inhibited after being exposed to sublethal stress. The isolates were resistant to most antimicrobials. The sanitizer concentrations necessary to eliminate V. vulnificus were higher than those usually used in the fishing industry.

Use of a species-rich and highly eutrophic tropical estuary in the South Atlantic by Pleuronectiformes (Teleostei: Acanthopterygii)

Abstract: A total of 1,471 specimens of 16 species of flatfishes (Pleuronectiformes) were caught during 48 sampling campaigns between July 2005 and June 2007 at ten stations in Guanabara Bay, Rio de Janeiro, Brazil. Paralichthyidae was the dominant family, with Etropus crossotus as the dominant species. The outer stations, especially those on the western side of the lower estuary, were distinguished as a result of their higher abundance of flatfishes and number of species. The spatial distribution of E. crossotus and its population structure indicate that this species is an estuarine resident despite the apparent reduction in its area of occupation within the estuarine complex. Among the other species, nine were classified as marine stragglers (Achirus declivis, Bothus ocellatus, Cyclopsetta chittendeni, Etropus longimanus, Paralichthys orbignyanus, P. patagonicus, Syacium micrurum, Symphurus diomedeanus and Trinectes paulistanus) and three as estuarine opportunists (Bothus robinsi, Citharichthys macrops and Syacium papillosum); another three could not be classified due to the small number of captures or lack of previous data (S. tessellatus, A. lineatus and C. spilopterus).

Improvement of natural spawning of black flounder, Paralichthys orbignyanus (Valenciennes, 1839) by photothermal and salinity conditioning in recirculating aquaculture system

Black flounder (Paralichthys orbignyanus) is an important commercial and recreational species inhabiting marine and estuarine waters from Rio de Janeiro (Brazil) to San Matías Gulf (Argentina) from 1 to 30 m depth, with a great potential for aquaculture in coastal or internal brackish waters. It is an estuarine-dependent species whose adults reproduce in marine water during the spring and summer. Since 2003, the reproduction of flounder broodstock in a recirculating aquaculture system (RAS) subject to a photothermal period and constant salinity of 34 psu has been carried out at the National Institute for Fisheries Research and Development (INIDEP). Final maturation of broodfish was regularly achieved through the use of a photoperiod and water temperature regimen simulating natural seasonal changes over a 10-month period, reaching 19–20 °C and 16 h L:8 h D by February. These spawning events were unstable and unpredictable, with wide variations in quality and quantity of eggs. Control of the reproductive cycle and development of cultured broodstocks are basic requirements for a successful aquaculture industry. In order to acquire a more precise control of egg production, the effect of salinity variation upon the quantity and quality of spawning eggs of the flounder broodstock in a RAS during three reproductive seasons was evaluated. For that purpose, salinity was changed according to photoperiod and temperature variations along the year as: a) fall-winter, 16–12 °C, salinity 25–15 psu, natural photoperiod at low light intensity (10 lx), and b) spring-summer, 16–19 °C, salinity 15–34 psu, artificial photoperiod and mean light intensity (200 lx). The result of the present study indicated that the combination of photothermal and salinity regimes effectively extended reproductive activity in the broodstock tank and increased both the number of spawning events and the amount of eggs in relation to previous years. 2015–2016 and 2016–2017 reproductive seasons lasted for >150 days, reporting a total of 52 and 53 spawning events and reaching 14,289,661 and 17,593,888 eggs released, of which 37.8% and 32.5% were viable eggs, respectively. The 2017–2018 reproductive season lasted 106 days with 55 spawning events and 27,548,896 eggs released (61.0% viable eggs), reaching the greatest number of total eggs obtained in any season at INIDEP since 2003.

Oxidative stress and antioxidant responses in juvenile Brazilian flounder Paralichthys orbignyanus exposed to sublethal levels of nitrite

This study evaluated the effects of short-term exposure to sublethal levels of nitrite on oxidative stress parameters and histology of juvenile Brazilian flounder Paralichthys orbignyanus. An assessment of fish recovery was also performed. Fish were exposed to 0.08 (control), 5.72, 10.43, and 15.27 NO2-N mgL-1 for 10days followed by the same recovery time. Gill, liver, and muscle samples were collected after 1, 5, and 10days of exposure and after recovery for the measurement of antioxidant capacity against peroxyl radicals (ACAP), glutathione-S-transferase (GST) activity, content of non-protein (NPSH) and protein thiols (PSH), and lipid peroxidation levels by thiobarbituric acid-reactive substances (TBARS) content. Nitrite exposure induced alterations which compromised the overall antioxidant system (reduced ACAP and GST activity) and enhanced oxidative damage in lipids and proteins. Increases in GST activity and NPSH and PSH contents were also demonstrated. The recovery period allowed for resumption of basal levels for all (treatment 5.72 NO2-N mgL-1) or some of the evaluated parameters (other treatments). In conclusion, exposure to nitrite concentrations from 5.72 to 15.27 NO2-N mgL-1 induced oxidative stress and antioxidant responses in juvenile Brazilian flounder. The 10-day recovery period was sufficient for a complete resumption of basal physiological condition of fish exposed to concentrations of up to 5.72 NO2-N mgL-1.

Pterobothrium crassicolle parasitizing Paralichthys orbignyanus (Osteichthyes, Paralichthyidae) in Brazil.

From September 2014 to November 2015, 30 Paralichthys orbignyanus specimens were obtained from Sepetiba Bay in the municipality of Rio de Janeiro, State of Rio de Janeiro, Brazil. The fishes were necropsied and cestode larvae were recovered from the abdominal cavity, mesentery, and serosas of the stomach, intestine, spleen, liver, kidney and gonads. Nineteen fish were parasitized by a total of 90 trypanorhynch plerocerci. Based on morphological characters, these were identified as Pterobothrium crassicolle. The parasitism indices for P. crassicolle on P. orbignyanus, were 63.3% for prevalence, 4.7 for mean intensity, 3 for mean abundance and 1 to 18 for range of infection. These parasites were studied due to their importance during fish sanitary inspection, if one considers the harm that the repulsive aspect of infected fish may cause to consumers. This is the first record of P. crassicolle plerocerci parasitizing P. orbignyanus.

Effects of agar films incorporated with fish protein hydrolysate or clove essential oil on flounder (Paralichthys orbignyanus) fillets shelf-life

This study evaluated the effect of protein hydrolysate (PH) and clove essential oil (CEO) on agar film properties and the shelf-life improvement of flounder fillets. Firstly, Argentine croaker muscle protein was alkali-solubilised and recovered to obtain a stable substrate. This substrate was hydrolysed to 20% degree of hydrolysis, by Alcalase (A20) and Protamex (P20). The molecular weight (MW) distribution, amino acid and in vitro antimicrobial activity of these hydrolysates were tested. Agar films were prepared with and without (control) incorporation of PH (A20 hydrolysate) or CEO and characterised by mechanical properties, water vapour permeability, solubility and optical properties. The microbiological, physical and chemical properties of flounder fillets coated with these films were monitored during storage at 5 °C for 15 days. Compared to P20, A20 hydrolysate possessed lower MW, higher hydrophobic amino acid content and the most effective antimicrobial activity against selected pathogens, such as Staphylococcus aureus, Yersinia enterocolitica, Aeromonas hydrophila, Debaryomyces hansenii and Listeria innocua. The presence of PH increased the water solubility, water vapour permeability, elongation at break and yellowness of the films. The CEO films possessed less transparency than PH films and control films, due to the presence of oil in the formulations. Fillets covered with PH and CEO films, especially the latter, presented lower total volatile bases and pH values, and delayed considerably the growth of H2S-producing microorganisms compared to the control films. The CEO might be used as a natural biopreservative to extend the flounder shelf-life. However, further studies are necessary, to assess the antimicrobial effect of PH when used as food packaging.

Abnormalities in flatfishes of the south-west Atlantic Ocean.

Five adult paralichthyid specimens with various kinds of abnormalities are reported from the south-west Atlantic Ocean. These abnormal flatfish specimens represent the first records of wholly ambicoloured Paralichthys orbignyanus specimens having a deep notch between the eye and dorsal fin and a partially albinistic specimen having skeletal deformities and only the second record of an almost totally ambicoloured specimen. We also report the first observation of reversal in Paralichthys patagonicus and an almost totally ambicoloured, reversed Xystreurys rasile.

Secondary Stress Responses in Juvenile Brazilian Flounder, Paralichthys orbignyanus, throughout and after Exposure to Sublethal Levels of Ammonia and Nitrite

AbstractThis study investigated the secondary stress responses of Paralichthys orbignyanus exposed to ammonia and nitrite and after recovery. Fish were exposed to 0.12, 0.28, and 0.57 mg NH3‐N/L, or 5.72, 10.43, and 15.27 mg NO2‐N/L for 10 d followed by the same time length for recovery. Ammonia‐ and nitrite‐free water was used as a control treatment. Blood samples were collected after 1, 5, and 10 d of exposure and after recovery. Fish exposed to ammonia presented lower and higher glucose levels after 10 d of exposure and recovery, respectively. Ammonia induced initial and transient ionic disturbances and metabolic alkalosis. Nitrite exposure caused hyperglycemia, increased plasma K+ levels, and respiratory alkalosis, whereas metabolic acidosis was observed after recovery. Increased proportion of monocytes and/or granulocytes and reduced number of lymphocytes were demonstrated in fish exposed to 0.28 mg NH3‐N/L (Day 1) and 10.43 mg NO2‐N/L (Day 5) and after recovery in the 0.28 and 0.57 mg NH3‐N/L treatments. Exposure to ammonia decreased the proportion of granulocytes on Day 5. In conclusion, exposure to concentrations at 0.12 mg NH3‐N/L and 5.72 mg NO2‐N/L provoked physiological disorders in Brazilian flounder. Nonetheless, fish exposed to 5.72 mg NO2‐N/L following a 10‐d recovery period showed complete resumption of homeostasis.

Characterization of digestive enzymes from captive Brazilian flounder Paralichthys orbignyanus.

Knowledge of specific enzyme activity, along with animal habits and digestive capacity is essential in formulating an appropriate diet for any species. In this study, we evaluated and characterized the activity of digestive enzymes present in the liver, intestine, and stomach of Paralichthys orbignyanus. The effects of pH and temperature on enzyme activity were also evaluated via the use of specific substrates. The use of specific substrates and inhibitors showed strong evidence of the presence of trypsin (BApNA= 0.51 ± 0.2 mU mg-1), chimotrypsin (SApNA= 2.62 ± 1.8 mU mg-1), and aminopeptidases (Leu-p-Nan =0.9709 ± 0.83 mU mg-1) in the intestine. Optimum pH for the activity of trypsin, chemotrypsin, leucino aminopeptidase, amilase, and pepsin were 9.5, 9.0, 8.0, 7.5, and 3.5, respectively, while optimum temperatures were 50, 50, 50, 40, and 45 °C, respectively. These results provide additional information regarding the biology of Brazilian flounder and can be used as a basis for further studies regarding fish feeding physiology.

Ammonia exposure and subsequent recovery trigger oxidative stress responses in juveniles of Brazilian flounder Paralichthys orbignyanus.

The effects of ammonia exposure and recovery on oxidative stress parameters and histology of juvenile Brazilian flounder Paralichthys orbignyanus were evaluated. The fish were exposed to 0.12, 0.28 and 0.57mgNH3-NL-1, plus a control, for 10days followed by the same recovery time in ammonia-free water. Gill, liver and muscle samples (n=9) were collected after 1, 5 and 10days of exposure and after recovery for oxidative stress analysis (antioxidant capacity against peroxyl radicals (ACAP); glutathione S-transferase (GST) activity; lipoperoxidation levels measured through thiobarbituric acid reactive substances (TBARS) content). For histological assessment, gill, liver and brain samples were collected. Exposure to all NH3-N concentrations induced different time- and dose-dependent changes in oxidative stress parameters. Reduced antioxidant capacity of the liver and muscle and enhanced TBARS levels in the gills and liver were demonstrated. Differently, a high ammonia concentration elicited lower hepatic TBARS levels. Enhanced GST activity in all organs and increased antioxidant capacity of the gills were also observed. No ammonia-induced histopathological effects were demonstrated. After recovery, most parameters (liver ACAP, GST activity in the muscle and liver and TBARS in the gills) returned to baseline levels. However, liver TBARS and gill GST activity remained altered 0.57mgNH3-NL-1 treatment. The recovery period also led to a decrease in gill antioxidant capacity and an increase in muscle antioxidant capacity. In conclusion, a concentration of 0.12mgNH3-NL-1 induces oxidative stress and antioxidant responses in juvenile Brazilian flounder. Moreover, a 10-day recovery period is not sufficient to restore fish homeostasis.

Tracing Cr, Pb, Fe and Mn occurrence in the Bahía Blanca estuary through commercial fish species

Over the last decades the anthropogenic contamination impact has substantially increased in the Bahía Blanca estuarine area, and scarce information exists regarding metals in the biotic compartment of this estuary. Thus, fish tissues were used to evaluate metal accumulation within this aquatic environment. The study focused on the determination of Cr, Pb, Fe and Mn in the gills, liver and muscle tissues of six commercial fish species (Brevoortia aurea, Odontesthes argentinensis, Micropogonias furnieri, Cynoscion guatucupa, Mustelus schmitti and Paralichthys orbignyanus).From the results it can be summarized that C. guatucupa tends to accumulate higher metal levels in the liver tissues, mostly Cr and Fe, than the other studied species. O. argentinensis and P. orbignyanus, both permanent inhabitants of the BBE, achieved the highest metal values in the gill tissues, mostly in comparison to M. schmitti. The gill tissues were found to be the main organ of Mn and Ni accumulation for most species, whereas in general, minimum concentrations were found for all the analyzed metals in the muscle tissues. Nevertheless, and according to the guidelines, all fish species showed at least one sample with concentrations of Mn and/or Cr above the permissible levels for human consumption.Finally, it was highlighted the usefulness of selecting these fish species as bioindicators of metal pollution, since they are either permanent inhabitants of the estuary or, according to the sizes under analyses, spend much of their time in this coastal waters.