Seasonal modulation of oxidative stress biomarkers in mangrove oyster (Crassostrea gasar) from an Amazon estuary.

Estuaries are the final destination of many pollutants derived from anthropogenic activity. Therefore, it is difficult to find this kind of ecosystem in a pristine condition. In this context, biomonitoring studies that characterize the organism's conditions against the environment' s natural variation are essential for future impact analysis due to anthropic activity. The present study aims to characterize the natural modulation of biochemical biomarkers in oysters Crassostrea gasar. The research was conducted in Japerica Bay, an estuary region located in the Eastern Amazon (Pará, Brazil), which has remained in pristine condition for many years. The samplings were carried out throughout one year during the rainy-dry transition period (June/2013), dry period (September/2013), dry-rainy transition period (November / 2013), and rainy period (February / 2014) in the lower and upper estuary. The activity of glutathione-S-transferase (GST) and total antioxidant capacity (ACAP) were evaluated as biomarkers of exposure and lipid peroxidation (LPO) as an effect biomarker. In gills, GST decreased during the rainy season in both sites and increased during the salinity peak (dry-rainy transition period) for the upper estuary's organisms. In this organ, the lowest levels of LPO occurred during the dry season for both points. There was an induction of ACAP in muscle during the rainy-dry transition period compared to the dry and dry-rainy transition periods for the lower estuary's organisms, and there were no differences for GST suggesting low tissue sensitivity. There was an increase in LPO during the rainy season compared to the rainy-dry transition period for the lower estuaries animals. Biomarkers in gills suggest a metabolic challenge to the rainy season and stability during the dry season. The species shows high viability of use in biomonitoring programs. However, these seasonality-induced alterations in biomarkers responses must be taken into account to interpret the results.

Salt transport by the gill Na+-K+-2Cl- symporter in palaemonid shrimps: exploring physiological, molecular and evolutionary landscapes.

Palaemonid shrimps inhabit osmotic niches from marine to continental waters. They hyper-regulate hemolymph osmolality and ionic concentrations in dilute media, hypo-regulating in concentrated media. Their gill epithelia express ion transporters like the Na+-K+-2Cl- symporter (NKCC) thought to play a role in salt secretion. To examine Cl- hypo-regulatory capability and phylogenetic correlations between gill NKCC mRNA levels and protein expression, we used palaemonids ranging from marine tide pools through estuaries (Palaemon) to coastal and continental fresh waters (Macrobrachium). We established the species' upper critical salinity limits (UL50) and short- (24 h) and long-term (120h) hypo-regulatory abilities at salinities of 80% of their UL50's (80%UL50). The Palaemon species exhibited the highest UL50's and greatest hypo-regulatory capabilities; among the Macrobrachium species, UL50's were higher in the diadromous than in the hololimnetic species. While basal transcript levels of gill NKCC mRNA were highest in P. pandaliformis, levels were unaffected by salinity or exposure time in all species. However, gill NKCC protein abundance increased after 120-h exposure at the 80%UL50 in all Macrobrachium species, except M. potiuna. Unexpectedly, hemolymph hyper-osmoregulatory capability in acclimatization media correlated with gill NKCC protein synthesis, while gill NKCC mRNA expression correlated with hemolymph hyper-Cl- regulation in Macrobrachium. These findings, together with the evolutionary history of osmoregulation in this shrimp clade, suggest a role for the gill NKCC symporter in both salt uptake and secretion. The evolution of NKCC protein expression responsiveness, unlike hemolymph hypo-regulation and NKCC mRNA expression, may have been driven by environmental salinity during niche radiation. SUMMARY STATEMENT: While mRNA expression of the gill Na+-K+-2Cl- symporter is unchanged during acclimation of palaemonid shrimps to saline media, protein expression is up regulated, revealing a role in chloride secretion.

Combined hypoxia and high temperature affect differentially the response of antioxidant enzymes, glutathione and hydrogen peroxide in the white shrimp Litopenaeus vannamei.

Low oxygen concentration in water (hypoxia) and high temperature are becoming more frequent due to climate change, forcing animals to endure stress or decease. Hypoxia and high temperature stress can lead to reactive oxygen species (ROS) accumulation and oxidative damage to the organisms. The shrimp Litopenaeus vannamei is the most cultivated crustacean worldwide. The aim of this study was to evaluate the expression and enzymatic activity of glutathione peroxidase (GPx), catalase (CAT) and cytosolic manganese superoxide dismutase (cMnSOD) in gills and hepatopancreas from L. vannamei in response to two combined stressors: hypoxia and reoxygenation at control and high temperature (28 vs 35 °C, respectively). In addition, glutathione and hydrogen peroxide content were analyzed. The changes were mainly tissue-specific. In gills, cMnSOD expression and enzymatic activity increased in response to the interactions between oxygen variation and thermal stress, while GPx and CAT were maintained. More changes occurred in GPx, CAT and MnSOD in hepatopancreas than in gills, mainly due to the effect of the individual stress factors of thermal stress or oxygen variations. On the other hand, the redox state of glutathione indicated that during high temperature, changes in the GSH/GSSG ratio occurred due to the fluctuations of GSSG. Hydrogen peroxide concentration was not affected by thermal stress or oxygen variations in hepatopancreas, whereas in gills, it was not detected. Altogether, these results indicate a complex pattern of antioxidant response to hypoxia, reoxygenation, high temperature and their combinations.

Involvement of the phosphoryl transfer network in gill bioenergetic imbalance of pacamã (Lophiosilurus alexandri) subjected to hypoxia: notable participation of creatine kinase.

Hypoxia is among the most critical environmental stressors for fish in aquatic environments, and several energetic alterations have been associated with it. The aim of the present study was to evaluate the involvement of the phosphoryl transfer network and its effects on adenosine triphosphate (ATP)-dependent enzymes during hypoxia, as well as the role of oxidative stress in the activity of the phosphoryl transfer network in pacamã (Lophiosilurus alexandri) subjected to severe hypoxia. Branchial creatine kinase (CK; cytosolic and mitochondrial fractions), adenylate kinase (AK), and pyruvate kinase (PK) activities were inhibited after 72 h of exposure to hypoxia compared to their respective normoxia groups, and remained low (except for AK) after 24 and 72 h of re-oxygenation. Activities of the branchial sodium-potassium pump (Na+, K+-ATPase) and proton pump (H+-ATPase) were inhibited in fish exposed to 72 h of hypoxia compared to the normoxia group, remained inhibited after 24 h of re-oxygenation, and were restored to physiological levels after 72 h of re-oxygenation. Levels of branchial reactive oxygen species (ROS) were higher in fish exposed to hypoxia for 72 h compared to the normoxia group, and increased during re-oxygenation. Lipid peroxidation (LOOH) levels were higher in fish subjected to 72 h of hypoxia compared to the normoxia group, and remained higher during re-oxygenation. On the other hand, protein sulfhydryl (PSH) levels were lower in fish exposed to hypoxia for 72 h compared to the normoxia group, and remained low during re-oxygenation. Based on this evidence, inhibition of the activities of enzymes belonging to phosphoryl transfer network contributed to impairing energetic homeostasis linked to ATP production and ATP utilization in gills of pacamã subjected to hypoxia, and remained inhibited during re-oxygenation (except AK activity). Moreover, inhibition of the phosphoryl transfer network impaired activity of ATP-dependent enzymes, which can be mediated by ROS overproduction, lipid peroxidation, and oxidation of SH groups.

Respiratory control of acid-base status in lungfish.

The acid-base status is a tightly regulated physiological process, resulting from a balance of ions in the organism relevant to acid-base. The efficiency of the regulatory systems importantly determines the compensatory pH changes for a given disturb. Vertebrates minimize (or compensate) an acid-base disturb by general processes, which include ion transfer and/or PCO2 changes. Acid-base adjustment in fish is predominantly achieved by branchial exchange of acid-base relevant ions with correlated change in plasma HCO3- levels. Conversely, land vertebrates change blood PCO2 through ventilatory process and hence respiratory control of acid-base regulation plays an important role as a compensatory mechanism. Lungfishes (Dipnoi) have central position on vertebrate's evolution being considered as the sister group to the tetrapods. With an aquatic life mode, lungfish share similarities of respiratory function with tetrapods. This article reviews evidence showing that lungfish's respiratory system regulates acid-base status, like terrestrial ectothermic vertebrates. In the South American lungfish, Lepidosiren paradoxa, the presence of central CO2/pH chemoreceptors was unequivocally described. Also, the blood PCO2 and acid-base status are typical of a terrestrial vertebrate. These aspects are discussed under different environmental conditions that require respiratory acid-base adjustments, such as, exposure to hypercarbia, hypoxia, high temperature and aestivation. Interesting questions regarding the location and cell phenotype of CO2/pH central and peripheral chemoreceptors remain an open field to be explored in lungfish.

Fgf- and Bmp-signaling regulate gill regeneration in Ambystoma mexicanum.

Gill regeneration has not been well studied compared to regeneration of other appendages, such as limb and tail regeneration. Here, we focused on axolotl gill regeneration and found that Fgf- and Bmp-signaling are involved in their gill regeneration mechanism. Axolotls have three pairs of gill rami, and each gill ramus has multiple gill filaments. The gills consist of mesenchyme rich in extracellular matrix and epidermis. The gill nerves are supplied from the trigeminal ganglia located in the head. Denervation resulted in no gill regeneration responses. Nerves and gills express Bmp and Fgf genes, and treating animals with Fgf- and Bmp-signaling inhibitors results in phenotypes similar to those seen in denervated gills. Inducing an accessory appendage is a standard assay in amphibian regeneration research. In our study, an accessory gill could be induced by lateral wounding, suggesting that thin axon fibers and mesenchymal Fgfs and Bmps contributed to the induction of the accessory structure. Such accessory gill induction was inhibited by the denervation. Exogenous Fgf2+Fgf8+Bmp7, which have been determined to function as a regeneration inducer in urodele amphibians, could compensate for the effects denervation has on accessory blastema formation. Our findings suggest that regeneration of appendages in axolotls is regulated by common Fgf- and Bmp-signaling cascades.

Osmo-ionic regulation and carbonic anhydrase, Na+/K+-ATPase and V-H+-ATPase activities in gills of the ancient freshwater crustacean Aegla schmitti (Anomura) exposed to high salinities.

Aeglidae anomuran crabs originated in the sea, but invaded and diversified in southern South American freshwater (FW) streams. We here aimed at examining their tolerance of increased salinity, after a long time of evolution in FW (~33 million years). Aegla schmitti were exposed to FW and dilute seawater of salinities 15, 20, and 25‰ for 1, 5 and 10 days. Mortality in 35‰ was also assessed. Hemolymph osmolality, Na+, K+, Cl-, and Mg2+ ions, and hydration levels of the abdominal muscle were assayed. The activities of the Carbonic Anhydrase (CA), Na+/K+-ATPase (NKA) and V-H+-ATPase (VHA) were also assayed in the gills. A. schmitti preserves osmoregulatory mechanisms of its marine ancestors. It is able to survive in high salinities (25‰) for at least 10 days. Mortality in 35‰ was of 56% after 1 day, and of 100% after 7 days. In 25‰, NaCl is apparently hyporegulated at all times, while hemolymph osmolality rises after 5 days. CA and NKA activities remained unchanged in all experimental conditions, while VHA activity decreased after 10 days in 25‰. Hemolymph NaCl data was compatible with either hyporegulation and/or putative influx of NaCl into cells for regulatory volume increase (RVI). Further studies should deepen the understanding of the roles of low permeabilities and saturation of high affinity uptake systems in truly FW decapods, in their responses to high salinities. Moreover, the fate of extracellular NaCl as secretion in true hypo-regulation and/or influx into cells for RVI should also be investigated.

Does dissolved organic carbon from Amazon black water (Brazil) help a native species, the tambaqui Colossoma macropomum to maintain ionic homeostasis in acidic water?

To assess how the quality and properties of the natural dissolved organic carbon (DOC) could drive different effects on gill physiology, we analysed the ionoregulatory responses of a native Amazonian fish species, the tambaqui Colossoma macropomum, to the presence of dissolved organic carbon (DOC; 10 mg l-1 ) at both pH 7.0 and pH 4.0 in ion-poor water. The DOC was isolated from black water from São Gabriel da Cachoeira (SGC) in the upper Rio Negro of the Amazon (Brazil) that earlier been shown to protect a non-native species, zebrafish Danio rerio against low pH under similar conditions. Transepithelial potential (TEP), net flux rates of Na+ , Cl- and ammonia and their concentrations in plasma and Na+ , K+ ATPase; v-type H+ ATPase and carbonic anhydrase activities in gills were measured. The presence of DOC had negligible effects at pH 7.0 apart from lowering the TEP, but it prevented the depolarization of TEP that occurred at pH 4.0 in the absence of DOC. However, contrary to our initial hypothesis, SGC DOC was not protective against the effects of low pH. Colossoma macropomum exposed to SGC DOC at pH 4.0 experienced greater net Na+ and Cl- losses, decreases of Na+ and Cl- concentrations in plasma and elevated plasma ammonia levels and excretion rates, relative to those exposed in the absence of DOC. Species-specific differences and changes in DOC properties during storage are discussed as possible factors influencing the effectiveness of SGC DOC in ameliorating the effects of the acid exposure.

Kinetic characterization of the gill (Na+, K+)-ATPase in a hololimnetic population of the diadromous Amazon River shrimp Macrobrachium amazonicum (Decapoda, Palaemonidae).

We provide a kinetic characterization of (Na+, K+)-ATPase activity in a posterior gill microsomal fraction from a hololimnetic population of the diadromous Amazon River shrimp Macrobrachium amazonicum. Sucrose density gradient centrifugation reveals two distinct membrane fractions showing considerable (Na+, K+)ATP-ase activity, but also containing other microsomal ATPases. Only a single immune-reactive (Na+, K+)-ATPase with Mr of ≈110 kDa is present that hydrolyzes ATP with VM = 130.3 ±â€¯4.8 nmol Pi min-1 mg protein-1 and K0.5 = 0.065 ±â€¯0.00162 mmol L-1, exhibiting site-site interactions. Stimulation by Na+ (VM = 127.5 ±â€¯5.3 nmol Pi min-1 mg protein-1, K0.5 = 5.3 ±â€¯0.42 mmol L-1), Mg2+ (VM = 130.6 ±â€¯6.8 nmol Pi min-1 mg protein-1, K0.5 = 0.33 ±â€¯0.042 mmol L-1), K+ (VM = 126.7 ±â€¯7.7 nmol Pi min-1 mg protein-1, K0.5 = 0.65 ±â€¯0.0079 mmol L-1) and NH4+ (VM = 134.5 ±â€¯8.6 nmol Pi min-1 mg protein-1, K0.5 = 1.28 ±â€¯0.44 mmol L-1) also obeys cooperative kinetics. Ouabain (KI = 0.18 ±â€¯0.058 mmol L-1) inhibits total ATPase activity by ≈70%. This study reveals considerable differences in the kinetic characteristics of the gill (Na+, K+)-ATPase in a hololimnetic population that appear to result from the adaptation of diadromous Macrobrachium amazonicum populations to different limnic habitats.

Variations in the immune and metabolic response of proactive and reactive Sparus aurata under stimulation with Vibrio anguillarum vaccine.

Environmental insults, such as exposure to pathogens, modulate the behavioural coping style of animals to stressors, and repeated exposure to stressful environments may lead to species-specific infection phenotypes. To analyse the influence of stress behavioural phenotypes on immune and metabolic performance, gilthead sea bream (Sparus aurata L.) were first screened for proactive and reactive coping styles. Once characterized, both behavioural phenotypes fish groups were bath vaccinated with bacterin from Vibrio anguillarum, an opportunistic widespread pathogen of fish. Gills and liver were sampled at 0 (control group), 1, 3 and 7 days post-vaccination. Immune-, oxidative stress- and metabolic-related transcripts (il1ß, tnfα, igm, gpx1, sod, cat, lpl, ghr1 and ghr2), metabolic endpoints (glucose, cholesterol and triglycerides), hepatic health indicators (aspartate aminotransferase, alanine transaminase and alkaline phosphatase), oxidative stress status (esterase activity, total antioxidant capacity and total oxidative status) and stress biomarkers (cortisol) were determined. Present results indicate that screening for coping styles in the gilthead sea bream segregated the two distinct phenotypes as expected: proactive and reactive. Results also indicate that under bath vaccination proactive fish show high immune response and lower metabolism, whereas reactive fish show low immune and higher metabolic responses.

The integument of the nonamphibious goby Gobionellus oceanicus: Its functional morphology and respiratory capacity.

Facultative air-breathing fish can exchange respiratory gases using an air-breathing organ (ABO), such as the oral cavity of the integument, during environmental hypoxia. The goby Gobionellus oceanicus inhabits areas subject to environmental hypoxia; however, its ABO is unknown. To investigate the respiratory potential of G. oceanicus, the gill and integument surface area, diffusion capacity, and their diffusion barrier thickness were measured. Our results show that although gill surface area is smaller than observed in other facultative air-breathing fish, but it has all features necessary to perform aquatic gas exchange. Additionally the integument of the palate has a short diffusion barrier thickness and a large calculated O2 -diffusion capacity suggesting that it functions as the ABO.

Larval development of Brycon amazonicus (Teleostei, Bryconidae) with a focus on locomotory, respiratory and feeding structures.

In the present work we describe the larval development of Brycon amazonicus, with emphasis on structures linked to swimming, respiration and feeding. We monitored from larval hatching (13 h post-fertilization) to juvenile stage. Formation of the oral cavity and differentiation of gill arches began within 4 h post-hatching (hph) and within 11 hph the primordium of the pectoral fin appeared. At 25 hph, the head was in a rectilinear position with a terminal mouth, when the onset of tooth formation appeared. At 35 hph, gill arches were covered by the operculum and branchiostegal membrane and cusps of teeth pierced the epithelium of the premaxilla and anterior dentary region. Sharp teeth were observed in the maxilla at 171 hph and the pelvic fin primordium appeared at 243 hph, with taste buds on the tongue and the roof of the buccopharyngeal cavity. At 579 hph, all structures related to swimming and food capture were formed. Exogenous feeding of the larvae started at 29 hph, before the endogenous reserves were used up and the development of efficient swimming ability, reflecting the species' need to increasingly specialize on prey capture.

Biochemical and molecular responses in oysters Crassostrea brasiliana collected from estuarine aquaculture areas in Southern Brazil.

Biochemical and molecular responses were evaluated in oysters Crassostrea brasiliana collected from three oyster farms, at Guaratuba Bay, southern Brazil, forming a pollutant gradient: Farm 1 (reference site - farther from the urban area), Farm 2 (intermediate site) and Farm 3 (nearest to the urban area). Oxidative stress markers, DNA damage and transcript levels of CYP2AU1, CYP2-like1, CYP2-like2, SULT-like, GPx-like, SOD-like, CAT-like, GSTmicrosomal-like, GSTomega-like, FABP-like and ALAd-like genes were analyzed in the gills. The levels of polycyclic aromatic hydrocarbons, linear alkylbenzenes and polychlorinated biphenyls were also evaluated in the soft tissues of the oysters and in the sediment of the Farms. Higher GSTomega-like, CYP2AU1 and FABP-like transcript levels, GR and G6PDH activities and lipid peroxidation levels were observed in oysters from Farms 2 and 3, suggesting pollutant effects on oysters. Alterations in oxidative stress markers also suggest a response against a prooxidant condition in C. brasiliana due to pollutant effects.

Anesthesia by sprinkling method in the gills of tambaqui Colossoma macropomum does not influence intensity and morphology of monogeneans / Anestesia por meio de aspersão nas brânquias de tambaqui Colossoma maropomum não influencia a intensidade e a morfologia de monogeneas

Abstract The present study evaluates the influence of anesthesia on the parasitic fauna of monogenea fish parasites, as its intensity and viability. Two experiments were conducted: Evaluation of an anesthetic method by sprinkling eugenol directly on gills and evaluation of monogenea motility and viability; Comparison of immersion and directly sprinkling on the gills with benzocaine and eugenol followed by evaluation on parasite intensity. The results suggest that the anesthetic sprinkling didn't interfere in the parasite motility, morphology and body surface integrity analyzed by fluorescence method. The monogenean intensity in the gills was lower in fish anesthetized by immersion method compared to the sprinkling method and the control group. This method of anesthesia can be used in parasitological studies.

Resumo O presente estudo avalia a influência da anestesia sobre a fauna parasitária de monogeneas em peixes, sua intensidade e sua viabilidade. Dois experimentos foram realizados: Avaliação de um método anestésico por aspersão eugenol diretamente nas brânquias e avaliação da motilidade das monogeneas e sua viabilidade; e Comparação entre imersão e aspersão diretamente nas brânquias com benzocaína e eugenol, seguido de avaliação sobre a intensidade parasitária. Os resultados sugerem que a aspersão do anestésico não interferiu na motilidade, morfologia, superfície corporal e integridade do parasita, analisadas pelo método de fluorescência. A intensidade de monogenéticos nas brânquias foi menor nos peixes anestesiados pelo método de imersão em comparação com o método de aspersão e o grupo controle. O método de anestesia por aspersão nas brânquias pode ser utilizado em estudos parasitológicos.

Low salinity-induced alterations in epithelial ultrastructure, Na+/K+-ATPase immunolocalization and enzyme kinetic characteristics in the gills of the thinstripe hermit crab, Clibanarius vittatus (Anomura, Diogenidae).

Fresh caught Clibanarius vittatus [SW, 31‰ salinity (S)] were acclimated to a dilute medium (15‰ S) for 10 days, employing silver staining to locate gill ion transporting tissue, immunofluorescence to localize the Na+/K+-ATPase α-subunit in the lamellae, and electron microscopy to portray ultrastructural changes in the gill epithelia. Na+/K+-ATPase activity was characterized kinetically in a gill microsomal fraction, including synergistic stimulation by NH4+ plus K+. Silver staining revealed that all 26 phyllobranchiate arthro- and pleurobranchiae participate in ion transport. Na+/K+-ATPase α-subunit staining was weak in SW crabs and distributed exclusively and irregularly within the intralamellar septal cells, particularly at the septal-pillar cell body junctions, and septal cell cytoplasm facing the hemolymph space. In 15‰ S crabs, α-subunit localization was intense, occupying the entire thickened septum. Pillar cells and flanges did not stain. Mitochondria and membrane foldings increased in the pillar cell flanges and intralamellar septal cells, greatly amplifying surface area. Only a single ATP binding site (VM  =  130.8 ± 10.5 nmol min-1 mg protein-1; K0.5  =  55.3 ± 1.7 µmol l-1) obeying Michaelis-Menten kinetics was disclosed. Na+/K+-ATPase activity was modulated by Mg2+, Na+, and NH4+, exhibiting site-site interactions; K+ modulation showed Michaelis-Menten kinetics. K+ plus NH4+ synergistically stimulated activity ≈ 1.7-fold. Ouabain inhibited total ATPase activity by ≈ 70% (KI  =  220-300 µmol l-1), revealing phosphohydrolytic activities other than the Na+/K+-ATPase. Despite ample phylogenetic separation, the phyllobranchiate lamellae of the Anomura and Caridea share many ultrastructural features, that is, an intralamellar septum and opposed abutting pillar cells, similar Na+/K+-ATPase distribution, and comparable kinetic characteristics. These findings suggest either convergent evolution at the structural and biochemical levels, or preservation of traits present in a remote common ancestor.

Anesthesia by sprinkling method in the gills of tambaqui Colossoma macropomum does not influence intensity and morphology of monogeneans.

The present study evaluates the influence of anesthesia on the parasitic fauna of monogenea fish parasites, as its intensity and viability. Two experiments were conducted: Evaluation of an anesthetic method by sprinkling eugenol directly on gills and evaluation of monogenea motility and viability; Comparison of immersion and directly sprinkling on the gills with benzocaine and eugenol followed by evaluation on parasite intensity. The results suggest that the anesthetic sprinkling didn't interfere in the parasite motility, morphology and body surface integrity analyzed by fluorescence method. The monogenean intensity in the gills was lower in fish anesthetized by immersion method compared to the sprinkling method and the control group. This method of anesthesia can be used in parasitological studies.

Oxidative Status Profile in Different Tissues of Parastacus brasiliensis promatensis (Crustacea, Decapoda, Parastacidae) over a Seasonal Cycle.

The objective of this study was to assess annual redox balance by quantifying activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST), as well as measuring lipid peroxidation levels by determination of thiobarbituric acid-reactive substances, in different tissues of male and female crayfish collected from an area little affected by anthropogenic impacts. A total of 37 male and 32 female of Parastacus brasiliensis promatensis were collected over an annual cycle, and gill, muscle, hepatopancreas, and gonad samples were harvested and subjected to the aforementioned analyses via spectrophotometry. Comparison of the annual oxidative status response profile in gill and in hepatopancreas between males and females revealed differences only in SOD activity. In abdominal muscle, this comparison revealed a distinct profile of SOD and GST activity, as well as of lipid peroxidation. SOD activity in gonads of females increased in the summer when compared to autumn; conversely, CAT and GST levels did not differ over the year. During reproduction, a possible increase of the energy requirements led to an increase in lipid peroxidation in all tested tissues, in males and females alike. It was least evident in female gonad tissue, which suggests this tissue type is relatively protected; within this context, one may establish a tissue-specific grading of Lipid Peroxidation intensity in females of the species during the spring: gonads < muscle < gills < hepatopancreas. Our results show that the responses of the defenses analyzed antioxidants, as well as lipid peroxidation levels, were sex and tissue dependent and a clear pattern of seasonal variation.

Gill denervation eliminates the barostatic reflex in a neotropical teleost, the tambaqui (Colossoma macropomum).

The baroreflex is one of the most important regulators of cardiovascular homeostasis in vertebrates. It begins with the monitoring of arterial pressure by baroreceptors, which constantly provide the central nervous system with afferent information about the status of this variable. Any change in arterial pressure relative to its normal state triggers autonomic responses, which are characterized by an inversely proportional change in heart rate and systemic vascular resistance and which tend to restore pressure normality. Although the baroreceptors have been located in mammals and other terrestrial vertebrates, their location in fish is still not completely clear and remains quite controversial. Thus, the objective of this study was to locate the baroreceptors in a teleost, the Colossoma macropomum. To do so, the occurrence and efficiency of the baroreflex were both analyzed when this mechanism was induced by pressure imbalancements in intact fish (IN), first-gill-denervated fish (G1), and total-gill-denervated fish (G4). The pressure imbalances were initiated through the administration of the α1-adrenergic agonist phenylephrine (100 µg kg(-1)) and the α1-adrenergic antagonist prazosin (1 mg kg(-1)). The baroreflex responses were then analyzed using an electrocardiogram that allowed for the measurement of the heart rate, the relationship between pre- and post-pharmacological manipulation heart rates, the time required for maximum chronotropic baroreflex response, and total heart rate variability. The results revealed that the barostatic reflex was attenuated in the G1 group and nonexistent in G4 group, findings which indicate that baroreceptors are exclusively located in the gill arches of C. macropomum.

Effects on the metabolism, growth, digestive capacity and osmoregulation of juvenile of Sub-Antarctic Notothenioid fish Eleginops maclovinus acclimated at different salinities.

In this study we assessed the influence of three different environmental salinities (5, 15 and 31 psu during 90 days) on growth, osmoregulation, energy metabolism and digestive capacity in juveniles of the Notothenioid fish Eleginops maclovinus. At the end of experimental time samples of plasma, liver, gill, intestine, kidney, skeletal muscle, stomach and pyloric caeca were obtained. Growth, weight gain, hepatosomatic index and specific growth rate increased at 15 and 31 psu and were lower at 5 psu salinity. Gill Na(+), K(+)-ATPase (NKA) activity presented a "U-shaped" relationship respect to salinity, with its minimum rates at 15 psu, while this activity correlated negatively with salinity at both anterior and posterior intestinal portions. No significant changes in NKA activity were observed in kidney or mid intestine. Large changes in plasma, metabolite levels and enzymatic activities related to energy metabolism in liver, gill, intestine, kidney and muscle were generally found in the groups exposed to 5 and 31 psu compared to the 15 psu group. Only the pepsin activity (digestive enzymes) assessed enhanced with environmental salinity, while pyloric caeca trypsin/chymotrypsin ratio decreased. This study suggests that juvenile of E. maclovinus presents greater growth near its iso-osmotic point (15 psu) and hyperosmotic environment (31 psu). Acclimation to low salinity increased the osmoregulatory expenditure as seen by the gill and anterior intestine results, while at high salinity, branchial osmoregulatory activity was also enhanced. This requires the mobilization of lipid stores and amino acids, thereby holding the growth of fish back. The subsequent reallocation of energy sources was not sufficient to maintain the growth rate of fish exposed to 5 psu. Thus, E. maclovinus juveniles present better growth efficiencies in salinities above the iso-osmotic point and hyperosmotic environment of this species, showing their best performance at 15 psu as seen by the main osmoregulatory and energy metabolism enzymatic activities.

Autonomic control of post-air-breathing tachycardia in Clarias gariepinus (Teleostei: Clariidae).

The African catfish (Clarias gariepinus) is a teleost with bimodal respiration that utilizes a paired suprabranchial chamber located in the gill cavity as an air-breathing organ. Like all air-breathing fishes studied to date, the African catfish exhibits pronounced changes in heart rate (f H) that are associated with air-breathing events. We acquired f H, gill-breathing frequency (f G) and air-breathing frequency (f AB) in situations that require or do not require air breathing (during normoxia and hypoxia), and we assessed the autonomic control of post-air-breathing tachycardia using an infusion of the ß-adrenergic antagonist propranolol and the muscarinic cholinergic antagonist atropine. During normoxia, C. gariepinus presented low f AB (1.85 ± 0.73 AB h(-1)) and a constant f G (43.16 ± 1.74 breaths min(-1)). During non-critical hypoxia (PO2 = 60 mmHg), f AB in the African catfish increased to 5.42 ± 1.19 AB h(-1) and f G decreased to 39.12 ± 1.58 breaths min(-1). During critical hypoxia (PO2 = 20 mmHg), f AB increased to 7.4 ± 1.39 AB h(-1) and f G decreased to 34.97 ± 1.78 breaths min(-1). These results were expected for a facultative air breather. Each air breath (AB) was followed by a brief but significant tachycardia, which in the critical hypoxia trials, reached a maximum of 143 % of the pre-AB f H values of untreated animals. Pharmacological blockade allowed the calculation of cardiac autonomic tones, which showed that post-AB tachycardia is predominantly regulated by the parasympathetic subdivision of the autonomic nervous system.