Silver Catfish Research Articles

Digestibility of vegetal energetic ingredients supplemented with phytase for silver catfish (Rhamdia voulezi)

The aim of this study was to evaluate the digestibility of nutrients in oats, rice grits and wheat middlings by the silver catfish (Rhamdia voulezi), with and without phytase. Two hundred eighty-eight fish were distributed in 24 tanks of 500L with tapered conical bottoms. The experimental design was completely randomized, represented by eight treatments and three replications. The treatments consisted of the development of eight diets (reference with and without phytase, oats with or without phytase, rice grits with or without phytase and wheat middlings with or without phytase) in a factorial scheme. The diets using the ingredients were composed of 70% of the reference diet and 30% of the ingredient. In the supplemented diets, we used 1500FTUKg−1 of phytase. We performed physico-chemical and mineral analyses of the ingredients, diets and feces and performed the reading of chromium oxide in the diets and feces. The supplement of 1500FTUKg−1 in the diet improves the coefficients of nutrient digestibility, mainly for oats and rice grits. Considering the feeds supplemented or not with 1500FTUKg−1 in the diet, the rice grits and wheat middlings have higher values of use of their nutrients and can be used more efficiently in feeding catfish (R. voulezi).

Effect of diphenyl diselenide diet supplementation on oxidative stress biomarkers in two species of freshwater fish exposed to the insecticide fipronil

The ability of diphenyl diselenide [(PhSe)2] to attenuate oxidative damage was evaluated in the liver, gills, brain, and muscle of carp (Cyprinus carpio) and silver catfish (Rhamdia quelen) experimentally exposed to fipronil (FPN). Initially, the fish were fed a diet without (PhSe)2 or a diet containing 3.0mg/kg of (PhSe)2 for 60days. After the 60-day period, the fish were exposed to 0.65µg/L of FPN for 192h. The results showed that carp exposed to FPN and not fed with (PhSe)2 exhibited acetylcholinesterase (AChE) inhibition in brain and muscle, and increased thiobarbituric acid-reactive substance (TBARS) in liver, gills, and brain. Furthermore, FPN decreased nonprotein thiols (NPSH) and δ-aminolevulinate dehydratase (δ-ALA-D) in carp liver and gills, and increased plasma glucose and protein levels. In silver catfish, FPN inhibited AChE and increased TBARS levels in muscle. In addition, glutathione S-transferase (GST) decreased in liver and muscle, and plasma glucose was increased. (PhSe)2 reversed some of these effects. It prevented the increase in TBARS levels in liver, gills, and brain in carp and in silver catfish muscle, and reversed the increase in plasma glucose levels in both species. Additionally, (PhSe)2 increased the NPSH levels in carp and silver catfish that had decreased in response to FPN exposure. However, (PhSe)2 was not effective in reversing the AChE inhibition in brain and muscle or the δ-ALA-D decrease in carp liver. Thus, (PhSe)2 protects tissues of both species of fish, mainly by preventing or counteracting the effects of FPN, on TBARS levels, antioxidants, and present anti-hyperglycemic property.

Growth of silver catfish ( Rhamdia quelen ) exposed to acidic pH at different humic acid levels

ABSTRACT: Humic substances are organic compounds that possess high molecular weight and are formed by the decomposition of plant materials. Humic substances comprise humic acids, fulvic acids and humin. Humic acids (HA) have shown to be able to provide some protection to biological membranes of fish in water with low pH, replacing the protective action of Ca2+. Thus, this studyaimed to observe growth of silver catfish ( Rhamdia quelen ) juveniles exposed to pHs 5.5 and 6.5 and to different levels of HA: 0, 10, 25 and 50mg L-1. Results showed that, irrespective of pH, HA was highly detrimental to silver catfish growth, since the higher the concentration of HA, the lower the weight gain and feed intake, resulting in lower biomass and lower specific growth rate of juveniles. Hence, HA is extremely damaging to the performance of silver catfish juveniles in the tested concentrations.

Effect of different dietary fiber concentrates on the metabolism and indirect immune response in silver catfish

This work aims at assessing the metabolic and immunologic indirect responses of the addition of dietary fiber as a prebiotic agent to the diets of silver catfish (Rhamdia quelen). Dietary fiber was concentrated from citrus pulp, brewery yeast biomass and linseed grains. These were prepared and included in diets, as well as a treatment control and a commercial diet containing prebiotic (Actigen®). During 50 days, 600 juveniles silver catfish were maintained in a water recirculation system and fed with experimental diets, three times a day. At the end of the test, the animals’ blood, liver, mucus and intestine were collected for determination of the metabolic and immunologic parameters. The experimental design was completely randomized, with five treatments and four replications; data were subjected to the analysis of variance, and the means were compared by the Tukey’s test (P<0.05). Fiber concentrates the differences in composition and physical-chemical properties, which resulted in differences in blood parameters, intestinal goblet cell counts, hepatic metabolic intermediates and mucoprotein production by fish. Yeast autolysate and linseed fiber provide prebiotic effects when added to silver catfish diets, bringing benefits to the metabolism and animal’s immune system.

The inclusion of soybean oil in the diets of silver catfish (Rhamdia quelen) in relation to growth quality and fillet aceptability

Normal 0 21 false false false MicrosoftInternetExplorer4 The aim of this study was to evaluate the inclusion of soybean oil in the diet of female silver catfish ( Rhamdia quelen ) and its effect on the growth, composition, lipid profile and fillet acceptability thereof. In this experiment, 144 fish (237.75 ± 22.35 g) were distributed among 18 tanks (280 L) for 80 days. The use of 10% soybean oil in the fishes’ diet promoted higher weights (373.82 g) and better feed conversion ratios (1.5) for female silver catfish. The soybean oil levels tested did not interfere with fillet acceptability. Increasing soybean oil in the diet increased the quantity of unsaturated fatty acids in the fillets, which enhanced their nutritional quality. The use of 10% soybean oil is recommended for the female silver catfish diet. /* Style Definitions */ table.MsoNormalTable {mso-style-name:Tabela normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:Times New Roman; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;}

Effect of smoking methods on microbial safety, polycyclic aromatic hydrocarbon, and heavy metal concentrations of traditional smoked fish from Lagos State, Nigeria

ABSTRACTA study was carried out to investigate the effect of smoking methods on microbial safety, polycyclic aromatic hydrocarbon, and heavy metal concentrations of traditional smoked fish from Lagos State, Nigeria. One hundred samples of fresh fish were obtained from 20 different fishing communities/processing centers. The fresh fish samples were divided into two batches: The first batch was smoked with drum kiln and the second batch was immediately taken to the Fish Hatchery Unit, Federal University of Agriculture, Abeokuta for smoking with convective kiln. Laboratory analyses were carried out on the two batches for: microbiological (Coliform, Fuugi, Listeria monocytogenes, Salmonella paratyphi and Staphylococcus aureus), polycyclic aromatic hydrocarbon and heavy metals (mercury, lead, cadmium and chromium). The results of the microbiological, polycyclic aromatic hydrocarbon and heavy metal analyses revealed that there were significant variations (p < 0.05) between them. LC count of fresh silver catfish, spotted tilapia, bonga shad, Nigerian tongue sole, and Guinea barracuda samples were 1.9 × 102, 1.7 × 102, 2.0 × 102, 2.1 × 102 and 2.6 × 102 cfu/g and their drum kiln smoked samples were 4.0 × 10, 5.3 × 101, 6.0 × 101, 12.2 × 101 and 7.4 × 101 cfu/g, respectively, while samples from convective smoking kiln contain no strain of Listeria monocytogenes. The concentrations of the six major PAHs (fluorene, anthracene, benzo [b] fluoranthene, benzo [a] anthracene, benzo [a] pyrene and benzo [ghi] perylene) in the drum-smoked fish exceeded the EU maximum level of 5.0 μg/kg for BaP permissible in smoked fish, while samples smoked by convective smoking kiln showed levels below 3.5 μg BaP/kg. The study also showed that the levels of the four heavy metals investigated in the smoked fish samples are generally below the maximum permissible levels set by World Health Organization for Hg (0.2 ppm), Pb (0.3 ppm), Cd (0.2 ppm), and Cr (0.5 ppm) and hence pose no risk to smoked fish consumers.

Oxidative stability during frozen storage of fillets from silver catfish (Rhamdia quelen ) sedated with the essential oil of Aloysia triphylla during transport

ABSTRACT: This research aimed to evaluate whether the essential oil of Aloysia triphylla (EOAT) used in vivo as a sedative in the water for transporting fish could increase the oxidative stability of silver catfish (Rhamdia quelen) fillets during frozen storage. The chemical composition of EOAT and of fillets from fish exposed to EOAT (0, 30 or 40µL L-1) were assessed. The pH and lipid oxidation parameters (conjugated dienes, CD; thiobarbituric acid-reactive-substances, TBARS) were evaluated in the fillets throughout the storage period (-18±2oC/17 months). The main compounds found in EOAT were α- and β-citral. Treatment with EOAT did not modify the proximate composition of the fillets, but 40µL L-1 EOAT reduced pH levels when compared to the control fillets (P&lt;0.05). Compared to the control fillets, the fillets from fish treated with 30 and 40µL L-1 EOAT had higher initial CD values (P&lt;0.05), whereas fillets from fish treated with 40µL L-1 EOAT had lower TBARS levels after 6, 9 and 17 months of storage (P&lt;0.05). Results indicated that use of EOAT as a sedative in silver catfish transport water delays the degradation of primary oxidation products (CD) into secondary products (TBARS) in the frozen fillets. This delay in the lipid oxidation rate may increase the shelf life of frozen fillets.

Quercetin in the diet of silver catfish: Effects on antioxidant status, blood parameters and pituitary hormone expression

We analysed the effects of quercetin-containing diet on blood parameters, antioxidant status and pituitary hormone expression in silver catfish. Diets containing three concentrations of quercetin (0, 0.15 and 0.30%) were provided to fish once a day. The results indicated that quercetin did not promote any significant change on the haematological and biochemical parameters measured. Fish that received the diet with quercetin presented decreased lipid peroxidation (LPO) (measured by lipid hydroperoxides and thiobarbituric acid reactive substances) in all tissues evaluated. On the other hand, the activity of antioxidant enzymes such as superoxide dismutase, catalase, glutathione peroxidase and glutathione S-transferase were higher in tissues of fish fed with diets containing quercetin. Additionally, the content of non-protein thiols, total reactive antioxidant potential and ascorbic acid were also higher in tissues of quercetin fed fish. Finally, there was no changes regarding cortisol levels and the expression of growth hormone, prolactin and somatolactin in fish fed with quercetin when compared with the control. Our results suggests that supplementation of silver catfish diet with quercetin is beneficial since it reduced the LPO and increased antioxidant capacity in vital tissues of fish without having any impact on haematological and biochemical parameters, and on pituitary hormone gene expression. Statement of relevanceWe propose quercetin as supplement in fish diets.

Effects of phosphorylated protein concentrate of pumpkin seed meal on growth and digestive enzymes activity of silver catfish (Rhamdia quelen)

The present study aimed to determine the growth and activity of proteolytic digestive enzymes of silver catfish (Rhamdia quelen) fed by replacing increased fish meal in the diet by either phosphorylated protein concentrate or pumpkin seed meal (PPCPS). Five experimental diets were formulated with levels: 0 (control), 25 (25% pumpkin seed meal (PSM) and 25% PPCPS) and 50% (50% PSM and 50% PPCPS). Crude protein from fish meal was replaced either by PSM or PPCPS crude protein. Each diet was fed to four replicate groups of silver catfish (initial weight 24 ± 0.46 g) to apparent satiation three times a day. Four orthogonal contrasts were applied to the biological assay data. When compared to other diets, the replacement of fish meal by either 25% or 50% of PPCPS in the diet of juvenile catfish does not change growth rates and promotes improvement in feed conversion. The use of PSM as a protein ingredient is not recommended due to its negative influence on fish growth. Thus, it can be concluded that the nutritional value of PSM can be improved by the simple chemical process of phosphorylation, yielding a protein concentrate (PPCPS) that may be used as a promising alternative ingredient.

Early biochemical biomarkers for zinc in silver catfish (Rhamdia quelen) after acute exposure.

Contamination of aquatic ecosystems by metals causes various biochemical changes in aquatic organisms, and fish are recognized as indicators of environmental quality. Silver catfish were exposed to six concentrations of zinc (Zn): 1.0, 2.5, 5.0, 7.5, 10.0 and 12.5mg/L for 96h to determine the mean lethal concentration (LC50). The value obtained was 8.07mg/L. In a second experiment, fish were exposed to concentrations of 1.0 or 5.0mg/L Zn and a control for 96h. Afterward, the tissues were collected for biochemical analysis. Lipid peroxidation, as indicated by thiobarbituric acid-reactive substance (TBARS), decreased in the liver and brain for all Zn concentrations tested, while in the gills TBARS levels increased at 1.0mg/L and declined at 5.0mg/L. Zn increased protein carbonyls in the muscle of silver catfish and decreased it in the other tissues. The enzyme superoxide dismutase increased in both exposed groups. However, catalase did not change. Glutathione S-transferase decreased in the liver and increased in the gills (1.0mg/L), muscle (5.0mg/L) and brain (1.0 and 5.0mg/L). Nonprotein thiols changed only in brain and muscle tissue. Zn exposure inhibited acetylcholinesterase (AChE) activity in the brain at both concentrations tested, but did not change it in muscle. Exposure to Zn inhibited the activity of Na(+)/K(+)-ATPase in the gills and intestine at both concentrations tested. Our results demonstrate that Zn alters biochemical parameters in silver catfish and that some parameters such as AChE and Na(+)/K(+)-ATPase could be considered as early biomarkers of waterborne Zn toxicity.

Antibody response in silver catfish (Rhamdia quelen) immunized with a model antigen associated with different adjuvants.

Adjuvants are essential to boost the immune response to inoculated antigen and play a central role in vaccine development. In this study, we investigated the efficacy of several adjuvants in the production of anti-bovine serum albumin (BSA) antibodies in silver catfish. Two hundred and seventy juvenile silver catfish (60–80 g) of both sexes were intraperitoneally vaccinated with BSA (200 µg/fish) alone or mixed to the following adjuvants: Freund’s complete adjuvant (FCA), Freund’s incomplete adjuvant (FIA), aluminum hydroxide (AlOH), Montanide, four types of cytosine-phosphate-guanine (CpG) oligodeoxynucleotides (ODNs) and three concentrations of β-glucan, and the immune enhancing property was evaluated by measuring anti-BSA antibodies in blood samples at biweekly intervals. Our results demonstrated that CpGs ODNs and β-glucan were as effective as classical adjuvants (FCA, FIA, AlOH and Montanide) in promoting anti-BSA antibodies and that the kinetics of antibody production induced by all adjuvants used in our study had a similar trend to that observed in other fish species, with a peak at 28 days post-vaccination. These results may be useful for the selection of adjuvants for vaccine formulation intended for silver catfish and for the development of vaccine and vaccination strategies to other fish species.

Effect of (+)-dehydrofukinone on GABAA receptors and stress response in fish model.

(+)-Dehydrofukinone (DHF) is a major component of the essential oil of Nectandra grandiflora (Lauraceae), and exerts a depressant effect on the central nervous system of fish. However, the neuronal mechanism underlying DHF action remains unknown. This study aimed to investigate the action of DHF on GABAA receptors using a silver catfish (Rhamdia quelen) model. Additionally, we investigated the effect of DHF exposure on stress-induced cortisol modulation. Chemical identification was performed using gas chromatography-mass spectrometry and purity was evaluated using gas chromatography with a flame ionization detector. To an aquarium, we applied between 2.5 and 50 mg/L DHF diluted in ethanol, in combination with 42.7 mg/L diazepam. DHF within the range of 10-20 mg/L acted collaboratively in combination with diazepam, but the sedative action of DHF was reversed by 3 mg/L flumazenil. Additionally, fish exposed for 24 h to 2.5-20 mg/L DHF showed no side effects and there was sustained sedation during the first 12 h of drug exposure with 10-20 mg/L DHF. DHF pretreatment did not increase plasma cortisol levels in fish subjected to a stress protocol. Moreover, the stress-induced cortisol peak was absent following pretreatment with 20 mg/L DHF. DHF proved to be a relatively safe sedative or anesthetic, which interacts with GABAergic and cortisol pathways in fish.

Ecology and Fish Biodiversity of Man-Made Lakes of Southern Benin (West Africa): Implications for Species Conservation and Fisheries Management

Man-made lakes are alternative and potential habitats for biodiversity conservation, fisheries and extensive aquaculture. We investigated the ecology and the fish community structure of two (2) sand-dragged man-made lakes, Lake Ahozon and Lake Bewacodji of Southern Benin, with implications for species conservation, fisheries management and aquaculture valorization. From August 2014 to July 2015, habitats conditions were evaluated and fishes were sampled monthly with seine, cast net, experimental gill net and hooks in the open water and aquatic vegetation habitats of both lakes. Overall, the water quality of Lake Ahozon was globally favorable for the growth and the survival of the fish resources whereas Lake Bewacodji exhibited a poor water quality indicated mainly by an acid pH (mean: 6.32 ± 0.58) and low dissolved oxygen concentrations (mean: 3.52 ± 1.25 mg/l) caused by dense floating plants, Nymphea sp mainly and huge daily dumping of domestic wastes. The study revealed low species richness, d = 5.89 and d = 3.87, and low species diversity, H’ = 0.76 and H’ = 0.48 for Lakes Ahozon and Bewacodji, respectively, with Lake Ahozon more diverse than Lake Bewacodji. The fish community of Lake Ahozon comprised six (6) species, 3 cichlids Sarotherodon galilaeus, Oreochromis niloticus and Tilapia guineensis, the silver catfish, Chrysichthys nigrodigitatus (Claroteidae), the African bonytongue, Heterotis niloticus (Osteoglossidae), and the African catfish, Clarias gariepinus (Clariidae). Numerically, S. galilaeus dominated Lake Ahozon and made 85.21% of the sample. In Lake Bewacodji, the fish composition comprised four (4) species, Sarotherodon galilaeus multifasciatus, the dominant species making numerically 91.58% of the total sample, T. guineensis, C. gariepinus and C. nigrodigitatus. With regard to trophic structure, the fish assemblages of both lakes were numerically dominated by planktinovores/ detritivores, mainly S. galilaeus, O. niloticus, T. guineensis and C. nigrodigitatus making together 99.46% of Lake Ahozon fish community, and S. galilaeus multifasciatus, T. guineensis and C. nigrodigitatus accounting together for about 98.59% of Lake Bewacodji. In Lake Ahozon, standard length (SL) frequencies histograms showed an unimodal size distribution for H. niloticus, the nile tilapia O. niloticus and C. gariepinus whereas the two cichlids, S. galilaeus and T. guineensis exhibited a bimodal size distribution. In Lake Bewacodji, S. galilaeus multifasciatus, C. nigrodigitatus and C. gariepinus exhibited an unimodal size distribution. A sustainable exploitation of both man-made lakes requires the implementation of an integrated management scheme which should include habitat restoration and protection plan, fisheries/aquacultural valorization, ecological sound agriculture/ecotourism and environmental monitoring.

Catalysis of Silver catfish Major Hepatic Glutathione Transferase proceeds via rapid equilibrium sequential random Mechanism

Fish hepatic glutathione transferases are connected with the elimination of intracellular pollutants and detoxification of organic micro-pollutants in their aquatic ecosystem. The two-substrate steady state kinetic mechanism of Silver catfish (Synodontis eupterus) major hepatic glutathione transferases purified to apparent homogeneity was explored. The enzyme was dimeric enzyme with a monomeric size of 25.6 kDa. Initial-velocity studies and Product inhibition patterns by methyl glutathione and chloride with respect to GSH-CDNB; GSH-ρ-nitrophenylacetate; and GSH-Ethacrynic acid all conforms to a rapid equilibrium sequential random Bi Bi kinetic mechanism rather than steady state sequential random Bi Bi kinetic. α was 2.96 ± 0.35 for the model. The pH profile of Vmax/KM (with saturating 1-chloro-2,4-dinitrobenzene and variable GSH concentrations) showed apparent pKa value of 6.88 and 9.86. Inhibition studies as a function of inhibitor concentration show that the enzyme is a homodimer and near neutral GST. The enzyme poorly conjugates 4-hydroxylnonenal and cumene hydroperoxide and may not be involved in oxidative stress protection. The seGST is unique and overwhelmingly shows characteristics similar to those of homodimeric class Pi GSTs, as was indicated by its kinetic mechanism, substrate specificity and inhibition studies. The rate- limiting step, probably the product release, of the reaction is viscosity-dependent and is consequential if macro-viscosogen or micro-viscosogen.

Length-Weight Relationship and Condition Factor of Silver Catfish ( Chrysichthys nigrodigitatus) from the Lower Reaches of the New Calabar River Niger Delta

Length-Weight Relationship and Condition Factor of Silver Catfish ( Chrysichthys nigrodigitatus) from the Lower Reaches of the New Calabar River Niger Delta

A new species of Trichodina Ehrenberg, 1830 (Ciliophora: Trichodinidae) from Rhamdia quelen (Siluriformes: Heptapteridae) and Gymnotus sp. (Teleostei: Gymnotidae) in Brazil.

The present study describes a new species of Trichodina found in the mucus of the body surface of 137 farmed and wild silver catfish (Rhamdia quelen) located in southern Brazil and in the gills of 99 banded knife fish (Gymnotus sp.) captured in the basin of Pantanal. Smears of the body surface mucus and gills were air dried at room temperature and impregnated with silver nitrate and stained with Giemsa for analysis of the adhesive disc, denticles and macronucleus. Characterized as a medium trichodinid, Trichodina quelenii n. sp. resembles T. heterodentata and T. acuta. It differs from T. heterodentata by the shape of the blade and from T. acuta by the lack of central circle. Furthermore, the distinct shape of the blade of T. quelenii n. sp. differs from all previously described species for the genus, leaving no doubt it is a new species.

Anesthetic activity of the essential oil of Ocimum americanum in Rhamdia quelen (Quoy &amp; Gaimard, 1824) and its effects on stress parameters

ABSTRACT The aim of this study was to evaluate the anesthetic activity of the essential oil (EO) of Ocimum americanum L. in silver catfish (Rhamdia quelen ). In the first experiment, the depressor effects and chemical composition of the leaf EO (LEO) and inflorescence EO (IEO) were compared. Juveniles (n = 10) were placed in aquaria containing different concentrations of EO (25 - 500 mg L-1) to determine the point at which anesthesia was induced and the length of the recovery period. In the following experiment, the effects of 300 and 500 mg L-1 LEO exposure on stress parameters (plasma cortisol, glucose and sodium levels) after air exposure for 1 min were assayed. Fish (n = 10 per sampling time) were sampled immediately or transferred to anesthetic-free aquaria until sampling (15, 30, 60 or 240 min). LEO was composed mainly of β-linalool and 1,8-cineole in similar proportions, whereas IEO showed β-linalool as major compound. Anesthesia was obtained in silver catfish with 200-500 mg L-1 between 4-8 min for LEO and 6-16 min for IEO. Lower EO concentrations did not reach anesthetic stage up to 30 min. LEO used as anesthetic prevented the cortisol increase and sodium loss induced by aerial exposure. Glucose levels were raised in catfish exposed to LEO compared to basal group (not air exposed) in almost all observation times. EO of O. americanum obtained from leaves was considered suitable to anesthetic procedures due to its fast induction and handling-induced stress prevention.

Rhamdia quelen (Quoy &amp; Gaimard, 1824), submitted to a stressful condition: effect of dietary addition of the essential oil of Lippia alba on metabolism, osmoregulation and endocrinology

ABSTRACT The aim of this study was to evaluate the effect of the essential oil of Lippia alba (EOLA) as a feed additive on ionoregulatory and metabolic parameters and pituitary hormones expression in silver catfish, Rhamdia quelen , submitted to a stressful condition (stocking density of 10.6 kg m-3 and limited space). Fish were fed with different concentrations of EOLA (0.0 - control, 0.25 and 0.50 mL kg food-1) for 20 days. Metabolic parameters were not affected by the diet, with the exception of alanine aminotransferase, which was higher in the liver of fish fed 0.50 mL EOLA kg food-1. Plasma ions and activity of H+-ATPase did not change, but fish fed 0.25 mL EOLA kg food-1 presented higher Na+/K+-ATPase activity. Somatolactin expression in the pituitary was higher in the fish fed 0.25 mL EOLA kg food -1, but the expression of growth hormone and prolactin did not change. Therefore, dietary EOLA does not exert a protective effect in R. quelen submitted to a stressful situation because it did not alter most measured parameters. The use of 0.25 mL EOLA kg food-1 seems to be more suitable than 0.50 mL EOLA kg food-1 since the latter may be related to liver damage.

Effect of water temperature and salinity in oviposition, hatching success and infestation of Aphanoblastella mastigatus (Monogenea, Dactylogyridae) on Rhamdia quelen.

Several environmental parameters may influence biological processes of several aquatic invertebrates, such as the Monogenea. Current analysis investigates oviposition, hatching success and infestation of Aphanoblastella mastigatus, a parasite of the silver catfish Rhamdia quelen at different temperatures (~ 24 and 28 °C) and salinity (by adding sodium chloride to water, at concentrations 0, 5 and 9 g/L) in laboratory. There was no significant difference in oviposition rate and in A. mastigatus infestation success at 24 and 28 °C. On the other hand, the concentration 9 g/L of sodium chloride in the water impaired the parasite's survival and the viability of the eggs. Results show that its usage is efficient as a possible prophylactic treatment. Eclosion rate of A. mastigatus's eggs was significantly higher at 28 °C, although it was significantly less from 5 g/L. Two oviposition peaks (06h15 and 18h15) occurred during a 24-hour period, or rather, during the highest variations in luminosity. Further studies are recommended with greater temperature intervals and more intense experimental infestations to verify the effects of temperature in the life span and infestation success of A. mastigatus.

Effects of diphenyl diselenide on growth, oxidative damage, and antioxidant response in silver catfish

The aim of this study was to evaluate the effects of dietary diphenyl diselenide [(PhSe)2] at different concentrations (1.5, 3.0, and 5.0mg/kg) on growth, oxidative damage and antioxidant parameters in silver catfish after 30 and 60days. Fish fed with 5.0mg/kg of (PhSe)2 experienced a significant decrease in weight, length, and condition factor after 30days and these parameters increased after 60days. Thiobarbituric acid reactive substances (TBARS) and protein carbonyl (PC) decreased in the liver of silver catfish supplemented with (PhSe)2 after 30days at all concentrations, while after 60days these parameters decreased in liver, gills, brain, and muscle. Supplementation with (PhSe)2 induced a decrease in catalase (CAT) activity from liver only after 60days of feeding. Superoxide dismutase (SOD) decreased at 5.0mg/kg after 30 and 60days and glutathione peroxidase (GPx) was enhanced at 1.5 and 3.0mg/kg after 30 and 60days. Silver catfish supplemented for 30days showed a significant increase in liver glutathione S-transferase (GST) at 3.0mg/kg, while after 60days GST activity increased in liver at 1.5, 3.0, and 5.0mg/kg and in gills at 3.0 and 5.0mg/kg of (PhSe)2. After 30days, non-protein thiols (NPSH) did not change, while after 60days NPSH increased in liver, gills, brain, and muscle. In addition, ascorbic acid (AA) levels after 30days increased in liver at three concentrations and in gills and muscle at 1.5mg/kg, while after 60days, AA increased at all concentrations in all and tissues tested. Thus, diet supplemented with (PhSe)2 for 60days could be more effective for silver catfish. Although the concentration of 5.0mg/kg showed decreased growth parameters, concentrations of 1.5 and 3.0mg/kg, in general, decreased oxidative damage and increased antioxidant defenses.