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.

Meniscal mineralisation in little spotted cats

Background: The aim of this study was to evaluate the stifle joints of little spotted cats in captivity using radiographic and CT studies. The hypothesis was that these animals would have meniscal mineralisation that could be detectable by imaging studies. Twelve intact little spotted cats (Leopardus tigrinus), 2 females and 10 males, aged from 1.5 to 11.11 years old and weighing 1.9-3.05 kg were studied. These animals, which were living in the Quinzinho de Barros Municipal Zoo, had no symptoms or known disease processes at the time of the study. The plain radiographs and computed tomography (CT) scans of both stifle joints were performed under general anaesthesia. Sequential transverse images were acquired on a spiral scanner.Results: No signs of articular disease were observed in any of the animals. Radiographically, the meniscal mineralisation was detected as an oval radiopacity in the cranial compartment on the mediolateral projection, located within the area of the medial meniscus. On craniocaudal projection, the mineralisation was more difficult to visualise. In one of the animals, it was not possible to identify the meniscal mineralisation in either of the stifle joints. Using CT, meniscal mineralisation was best identified in the transverse plane images.Conclusions: Meniscal mineralisation appears to be a normal anatomic feature in little spotted cats. © 2013 Rahal et al.; licensee BioMed Central Ltd.

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.

Changes during chilled storage of whole tilapia and short-term frozen storage of tilapia fillets

This study evaluated the physicochemical changes in Nile tilapia (n = 82, 373.71 ± 61.91 g) refrigerated for up to 92 h and in the frozen fillets. The tilapias were captured with nets, slaughtered by ice and water shock (1:1) in a temperature of approximately 2°C for 30 min, and stored refrigerated at 4°C in polystyrene boxes containing ice. The fish were filleted, and filets were weighed and frozen. The drip loss and protein were determined after 23 days of frozen storage. After 4 h of storage, all fish were in full rigor mortis. The pH of the muscles decreased for up to 45 h of the storage period. The fillets obtained from tilapia stored for more than 72 h lost more weight and protein. Thus, the filleting or processing of tilapia should be done before 72 h of cold storage, since deterioration of the fish starts to occur after this period. Copyright © Taylor & Francis Group, LLC.

Initial description of the phylogeography, population structure and genetic diversity of Atlantic spotted dolphins from Brazil and the Caribbean, inferred from analyses of mitochondrial and nuclear DNA

We provide initial information regarding the population structure and genetic diversity of Stenella frontalis from the Caribbean and southeastern Brazil from analyses of mitochondrial control region sequences and sequences from the first intron of the α-lactalbumin gene. Comparisons with previously described S. frontalis sequences showed a high number of haplotypes shared between populations throughout their distribution range. High diversity was found for southeastern Brazil and Caribbean samples, and population structure analyses indicate significant differentiation among population units at the FST level, but not at the ΦST level. Significant differentiation at the FST level was found between the Caribbean population unit and all other populations units. These results suggest historical or present connectivity between the Azores and Madeira and the southeastern Brazil groups and population differentiation between the Caribbean and southeastern Brazil, supporting the notion of two separate stocks in the waters around the Atlantic coast of South America. © 2013 Elsevier Ltd.

Structural enrichment reduces aggression in Tilapia rendalli

Environmental enrichment seeks to improve the behavior of captive animals. Few studies have developed enrichment strategies for fish, particularly for use in aquaculture. Environmental enrichment for territorial and aggressive animals has the potential to increase both the amount of defensible resources and the value of a disputed territory which can increase the level of aggression. This study evaluated this hypothesis for the redbreast tilapia, Tilapia rendaIli. We used a short-term approach for evaluation of fish aggressive behavior by recording it for 30 min after introduction of a pair of fish into each experimental aquarium. Our main finding was that the latency to start a fight was lower in an enriched environment, but the frequency of attacks was higher in a non-enriched environment (control). Furthermore, we observed clear hierarchical behavior (submissive dark stripes on the body and dominant light-colored bodies without stripes) only in the non-enriched environment. Structural enrichment of the environment for redbreast tilapia leads to decreased aggression and cohabitation without hierarchical dominance. © 2013 Copyright Taylor and Francis Group, LLC.

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.

Desempeño de tanques decantadores de sólidos en un sistema de recirculación para producción de tilapia

To compare the removal efficiency of solids, turbidity and apparent color between a conventional and a column settling tanks in a recirculating aquaculture system (RAS) for tilapia farming. Materials and methods. Tilapia with a stocking density between 30 and 33 kg/m3 were cultured in a RAS consisting of a water level control box, PVC piping system, three plastic tanks for culture, conventional horizontal flow settling tank (Con.ST), column vertical flow settling tank (Col.ST), three phase fluidized bed reactor, oxygen transfer reactor, air compressor, air blower, centrifugal pump. The Con.ST operated at a volume of 1.4 m3 and hydraulic retention time (HRT) of 2.94 h; and was drained weekly for washing and sludge collection, representing a 55%discharge of system water volume. The Col.ST operated with a volume of 0.30 m3 and HRT of 0.553 h. Three daily partial draining operations were executed, representing a discharge of 50% of the system volume. Results. The mean solids removal efficiencies were: 34.01 and 44.44%for total solids; 64.45 and 71.71% for suspended solids; 21.10 and 45.65% volatile solids; 65.51% and 62.79% for turbidity; and 56.37 and 50.91% for apparent color, respectively for Con.ST and Col.ST. Conclusions. The two settling devices are useful on removal of the studied parameters and presented similar performance on turbidity and apparent color removal; however, the Col.ST was more efficient than Con.ST for solids removal, requires less space, less volume and requires less discharge water volume, displaying feasibility for its use on RAS.

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.