Ventilatory frequency of Nile tilapia subjected to different stressors

Ventilatory frequency (VF) was investigated in the fish Nile tilapia, Oreochromis niloticus, subjected to confinement, electroshock or social stressor. Fish were allowed to acclimatize to tank conditions for 10 days (1 fish/aquarium). VF baseline was determined 5 days after adjustment had been started. At the 10th day of isolation, stressor effects on VF were assessed. The stressors were imposed during 60 min: pairing with a larger resident animal (social stressor), or gentle electroshock (AC, 20 V, 15 mA, 100 Hz for 1 min every 4 min), or space restriction (confinement). VF was quantified immediately after the end of the stressor imposition. Baseline of VF was not statistically different among groups. Social stressor clearly induced VF to increase, while an increased or decreased VF can be observed for both confinement and electroshock. However, fish tend to increase their VF in response to confinement and decrease in the case of electroshock. These results suggest that VF is a sensitive behavioural indicator for distinguishing stress responses in the fish Nile tilapia among different stressors. © 2006 Elsevier GmbH. All rights reserved.

Economic evaluation of nile tilapia juvenile production, feed with commercial ration and with primary production come from organic and inorganic fertilization

Study objective was to evaluate economically a Nile tilapia juvenile production, employing different feeding techniques. Tilapia fingerlings of 8g were stocked at 5 fish m-2 stocking in 50 and 150 m2 ponds, during 75 days. Treatments were: inorganic fertilization (P205 and N); organic fertilization (poultry manure) and commercial ration (32% CP). Water quality results were considered adequate for fish rearing. In juvenile production there were significant differences among treatments for individual final weight, medians were: for inorganic fertilization 12.92g (13.35g in 50 m2 and 12.49g in 150 m2); for organic fertilization 30.55g (33.69g in 50 m2 and 27.40g in 150 m2) and for commercial ration 51.23g (52.90g in 50 m2 and 50.15g in 150 m2). Survival rate ranged from 63 to 71%, with no statistic difference. Commercial ration was effective to bigger juvenile production, with a better market value. Costs considered in economic analyses were tilapia fingerlings, fertilizer, ration, labor and installation depreciation. Obtained information showed that juvenile production in 50 m2 ponds is not viable economically and, in 150 m2, production is viable only when commercial ration is used.

Biochemical biomarkers in Nile tilapia (Oreochromis niloticus) after short-term exposure to diesel oil, pure biodiesel and biodiesel blends

Fossil fuels such as diesel are being gradually replaced by biodiesel, a renewable energy source, cheaper and less polluting. However, little is known about the toxic effects of this new energy source on aquatic organisms. Thus, we evaluated biochemical biomarkers related to oxidative stress in Nile tilapia (Oreochromis niloticus) after two and seven exposure days to diesel and pure biodiesel (B100) and blends B5 and B20 at concentrations of 0.01 and 0.1mLL -1. The hepatic ethoxyresorufin-O-deethylase activity was highly induced in all groups, except for those animals exposed to B100. There was an increase in lipid peroxidation in liver and gills in the group exposed to the higher concentration of B5. All treatments caused a significant increase in the levels of 1-hydroxypyrene excreted in the bile after 2 and 7d, except for those fish exposed to B100. The hepatic glutathione-S-transferase increased after 7d in animals exposed to the higher concentration of diesel and in the gill of fish exposed to the higher concentration of pure diesel and B5, but decreased for the two tested concentrations of B100. Superoxide dismutase, catalase and glutathione peroxidase also presented significant changes according to the treatments for all groups, including B100. Biodiesel B20 in the conditions tested had fewer adverse effects than diesel and B5 for the Nile tilapia, and can be suggested as a less harmful fuel in substitution to diesel. However, even B100 could activate biochemical responses in fish, at the experimental conditions tested, indicating that this fuel can also represent a risk to the aquatic biota. © 2011 Elsevier Ltd.

Thiamin Requirement of Nile Tilapia, Oreochromis niloticus

Juvenile Nile tilapia, Oreochromis niloticus, were fed to apparent satiation twice daily with purified diets containing 0, 1.0, 2.0, 4.0, 8.0, and 16.0 mg/kg and 0, 2.0, 4.0, 8.0, 16.0, and 32.0 mg/kg of thiamin in separate 14- and 8-wk trials (Experiments 1 and 2, respectively). Fish fed the diet devoid of thiamin developed neurological disorders, anorexia, reduced growth, and feed efficiency and increased mortality (Experiment 2 only) within 4-6 and 8-10 wk for Experiments 2 and 1, respectively. Low red blood cell count (RBC) and hematocrit (Ht) were observed in fish fed the thiamin-deficient diet. Serum pyruvate was elevated in fish fed the thiamin unsupplemented diet. Serum lactate was not affected by dietary thiamin levels. Whole body protein was unaffected by dietary levels of thiamin. Body moisture and ash increased whereas body lipid decreased in fish fed the thiamin unsupplemented diets. None of these abnormalities were observed in fish fed the thiamin-supplemented diets. Using the response curves determined by PROC NLMIXED to estimate dietary thiamin levels required for various response variables, a dietary thiamin level of 3.5 mg/kg diet was adequate for optimum growth, feed intake and efficiency, survival, prevention of neurological symptoms, and maintaining normal levels of RBC, Ht, serum pyruvate, and proximate body composition. © 2011.

Hemoparasite and hematological parameters in Nile tilapia

The accelerated growth of finfish aquaculture has resulted in a series of health problems, including blood disorders by hemoparasites; there are scarce studies about these agents and their impact in actual intensive farming. The aim of this study was to identify and quantify the hemoparasites present in monocytes and erythrocytes in the blood of tilapia and their correlation with the hematological profile. Blood samples were collected from caudal vessels of 15 cage-reared Nile tilapia (Oreochromis niloticus), with 70 ± 10 g weight on average, from Itambaracá Municipality, Parana State, Brazil. The total red blood cells, mean corpuscular volume, hematocrit, total and differential white blood cells counts, and the number of thrombocytes were determined in blood smears stained with May-Grünwald-Giemsa-Wright and Quick Panoptic. The results showed the presence of pleomorphic cytoplasmic inclusions with corrugated appearance and basophilic staining, mainly in monocytes, suggesting Anaplasmataceae parasitemia and inclusions with the same morphological characteristics in erythrocytes of one Nile tilapia. The hematological analysis showed no significant difference (P < 0.05) between infected and not infected fish, and therefore, there was no correlation between parasitemia and hematological profile. These observations allow us to infer that the intracytoplasmic inclusions in monocytes and erythrocytes are compatible with the family Anaplasmataceae. There was no correlation between the blood profile and low level of parasitemia. © 2012 Springer-Verlag London.

Blood Cues Induce Antipredator Behavior in Nile Tilapia Conspecifics

In this study, we show that the fish Nile tilapia displays an antipredator response to chemical cues present in the blood of conspecifics. This is the first report of alarm response induced by blood-borne chemical cues in fish. There is a body of evidence showing that chemical cues from epidermal 'club' cells elicit an alarm reaction in fish. However, the chemical cues of these 'club' cells are restricted to certain species of fish. Thus, as a parsimonious explanation, we assume that an alarm response to blood cues is a generalized response among animals because it occurs in mammals, birds and protostomian animals. Moreover, our results suggest that researchers must use caution when studying chemically induced alarm reactions because it is difficult to separate club cell cues from traces of blood. © 2013 Barreto et al.

Environmental light color affects the stress response of Nile tilapia

We investigated the effects of environmental light colors (blue, yellow and white) on the stress responses (measured by changes in ventilatory frequency - VF) of Nile tilapia to confinement. After 7 days of light treatment, the VF was similar for fish in each color. On the 8th day, fish were confined for 15. min. After release, the post-confinement VF was measured six times (first period: 0, 2 and 4. min; second period: 6, 8 and 10. min). Irrespective of the light color treatment, confinement increased the VF to higher levels during the first post-confinement period than during the second one. When color was analyzed, irrespective of time, fish under white light increased their VF post-confinement, and blue light prevented this effect. We conclude that blue light is the preferred color for Nile tilapia in terms of reducing stress. This finding is in contrast to previous choice test studies that indicated that yellow is their preferred color. © 2012 Elsevier GmbH.

Short periods of fasting followed by refeeding change the expression of muscle growth-related genes in juvenile Nile tilapia (Oreochromis niloticus)

Muscle growth mechanisms are controlled by molecular pathways that can be affected by fasting and refeeding. In this study, we hypothesized that short period of fasting followed by refeeding would change the expression of muscle growth-related genes in juvenile Nile tilapia (Oreochromis niloticus). The aim of this study was to analyze the expression of MyoD, myogenin and myostatin and the muscle growth characteristics in the white muscle of juvenile Nile tilapia during short period of fasting followed by refeeding. Juvenile fish were divided into three groups: (FC) control, feeding continuously for 42. days, (F5) 5. days of fasting and 37. days of refeeding, and (F10) 10. days of fasting and 32. days of refeeding. At days 5 (D5), 10 (D10), 20 (D20) and 42 (D42), fish (n = 14 per group) were anesthetized and euthanized for morphological, morphometric and gene expression analyses. During the refeeding, fasted fish gained weight continuously and, at the end of the experiment (D42), F5 showed total compensatory mass gain. After 5 and 10. days of fasting, a significant increase in the muscle fiber frequency (class 20) occurred in F5 and F10 compared to FC that showed a high muscle fiber frequency in class 40. At D42, the muscle fiber frequency in class 20 was higher in F5. After 5. days of fasting, MyoD and myogenin gene expressions were lower and myostatin expression levels were higher in F5 and F10 compared to FC; at D42, MyoD, myogenin and myostatin gene expression was similar among all groups. In conclusion, this study showed that short periods of fasting promoted muscle fiber atrophy in the juvenile Nile tilapia and the refeeding caused compensatory mass gain and changed the expression of muscle growth-related genes that promote muscle growth. These fasting and refeeding protocols have proven useful for understanding the effects of alternative warm fish feeding strategies on muscle growth-related genes. © 2013.

Mannanoligosaccharide (mos) and β-glucan (β-glu) in dietary supplementation for Nile tilapia juveniles dept in cages

This experiment was conducted at an aquicolous enterprise with the objective of evaluating the use of MOS and β-GLU as dietary supplements in an experimental lot in order to follow the zootechnical performance, establishing a relationship with the hematological parameters, the morphological alterations of the intestine, and the enzymatic activity (protease, lipase and amylase), and the water quality of 3,000 tilapia juveniles kept in cages (Wt = 24 ± 0.26g). Nine cages (6.0 m3) were used, with three treatments and three replications. 1: commercial feed without supplementation (control); 2: 0.1% per ton of MOS; 3: 0.03% per ton of purified β-GLU. The feed contained 36% of crude protein (CP) incorporated into the premix MOS and purified β-GLU (BIORIGIN®). The tilapia that had received the diet supplemented with β-GLU in a period of 90 days showed a favorable condition of the immune system, increase in the absorption surface of the front part of the intestine and consequently, growth in the activity of the digestive enzymes, denoting higher efficiency in the use of the nutrients in juveniles, providing satisfactory zootechnical performance in comparison with the other diets. This product may be used as a dietary supplement for this species when kept in cages.

Branchial O2 chemoreceptors in Nile tilapia Oreochromis niloticus: Control of cardiorespiratory function in response to hypoxia

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Selenium fractionation from plasma, muscle and liver of Nile tilapia (Oreochromis niloticus)

This paper presents the results obtained from selenium fractionation in plasma, muscle and liver samples of Nile tilapia's (Oreochromis niloticus) after protein separation. The plasma, muscle and liver proteome was obtained by 2D-PAGE, and selenium in protein spots was qualitatively and quantitatively determined by synchrotron radiation X-ray fluorescence and graphite furnace atomic absorption spectrometry (GFAAS). The fluorescence spectra indicated the presence of selenium in three protein spots of plasma, two of muscle and one of liver. Selenium was found to be distributed mainly in proteins with a molar mass smaller than 57.0 kDa and with pI in the range of 5.9-9.6, with one exception in the plasma sample, which presented protein with a molar mass of 60.0 kDa. After acid mineralization of the protein spots, a GFAAS determination of the concentration of selenium bound to these proteins indicated a range of 1.35-6.82 mg per g of protein. © 2013 Springer Science+Business Media New York.

Effects of a homeopathic complex on the performance and cortisol levels in Nile tilapia (Oreochromis niloticus)

Background: Intensive fish farming results in stress adversely effecting the performance of farmed fish. Plasma cortisol is a validated measure of stress in fish. We evaluated the effect of a homeopathic complex on the cortisol level of Nile tilapias (Oreochromis niloticus). Method: 60 animals with approximate average weight of 100 g each at the start of experiment were randomly distributed in six glass fiber water tanks, capacity 1000 liters, with a daily water renewal rate of 20%. They received one of two treatments: 30 animals in control treatment and 30 animals receiving the homeopathic complex Homeopatila 100. On days 1, 30 and 60, all fish were anesthetized and blood was collected by puncture on the caudal vein, to determine the levels of circulating cortisol. Results: At the end of the experiment the fish receiving a homeopathic complex, had significantly lower circulating cortisol level (17.96 ng/mL ± 0.95) than the control group (38.68 ng/mL ± 1.21) (p < 0.05). Conclusions: Cortisol levels were significantly lower in the treated group than control, and the fish were larger in the treated group. © 2013 The Faculty of Homeopathy.

Paratrichodina africana (Ciliophora): A pathogenic gill parasite in farmed Nile tilapia

Trichodinids are ciliated protozoa that are widely known as one of the main groups of fish parasites. The genus Trichodina presents the greatest species diversity. However, records of Paratrichodina species are scarce, and little is known about their pathogenicity in hosts. The present study provides new records of Paratrichodina africana Kazubski and El-Tantawy (1986) in Nile tilapia from South America and descriptions of pathological changes and seasonality. A total of 304 farmed fish were examined. From gill scraping, parasites were identified using Klein's nitrate impregnation method. Gill samples were fixed for histopathological analysis. Small trichodinid found in this study have a prominent blade apophysis and narrow central part and blade shape that corresponds to the characteristics of P. africana Kazubski and El-Tantawy (1986). Gill lesions were proportional to parasite intensity, in which the gill tissue was compromised in heavy infestation. Proliferative disturbances were found, including epithelial hyperplasia, desquamation, and mononuclear and eosinophilic infiltrate that culminated in necrosis. We did not observe a seasonality effect on the occurrence of P. africana. This ciliated protozoan causes compromised respiratory capacity that leads to severe gill lesions and currently is an important pathogen that afflicts intensive tilapia cultures in Brazil. © 2013 Elsevier B.V.