Biochemical biomarkers in Oreochromis niloticus exposed to mixtures of benzo[a]pyrene and diazinon.

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

Hematological parameters in Nile Tilápia, Oreochromis niloticus exposed to sub-letal concentrations of mercury

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

Colina e betaína em rações purificadas na nutrição da tilápia do Nilo (Oreochromis niloticus)

Problemas metabólicos observados em produções intensivas de tilápias do Nilo (Oreochromis niloticus) têm sido relacionados à deficiência de colina nas rações. Com o objetivo de avaliar o efeito da suplementação dietética da colina na nutrição da espécie, rações purificadas contendo 0; 375; 750; 1.125; 1.500 ou 1.875 mg de cloreto de colina por kg, foram administradas ad libitum por 42 dias a tilápias do Nilo (5,09 ± 0,14 g), estocados em gaiolas de PVC atóxico (volume = 60 L), alojadas em caixas de polipropileno de 1000 L, em ambiente com condições controladas de temperatura e luminosidade, num delineamento experimental em blocos incompletos casualizados, com três parcelas por bloco (n=5). O ganho de peso (GDP) e o índice de conversão alimentar (ICA) de todos os tratamentos foram superiores ao controle. Não foram observadas diferenças para a quantidade de lipídios no fígado e tecido corporal, e sobrevivência (S%). Num segundo experimento, os peixes foram alimentados com rações suplementadas com 1.250 ou 2.500 mg de cloreto de colina por kg; ou 1.000; 2.000 ou 3.000 mg de betaína por kg. Não foram observadas diferenças significativas para S% e acúmulo de lipídeos hepáticos ou corporais; o ICA e GDP dos tratamentos suplementados com colina foram superiores aos dos tratamentos suplementados com betaína, mas não diferiram entre si. Níveis de suplementação superiores a 375 mg de cloreto de colina por kg de alimento melhoram o ICA e o GDP da tilápia do Nilo, mas a betaína não substitui efetivamente a colina em rações para a espécie.

Digestibilidade aparente e trânsito gastrintestinal em tilápia do Nilo (Oreochromis niloticus), em função da fibra bruta da dieta

Os efeitos de diferentes níveis de fibra bruta na digestibilidade aparente e velocidade de trânsito gastrintestinal de tilápias do Nilo alimentadas com dietas purificadas fornecidas foram avaliados. Utilizaram-se cinco aquários circulares (250 L) para alimentação, dotados de sistema fechado de filtragem, reabastecimento e aquecimento da água, e cinco aquários de digestibilidade (100 L), dotados de sistema individual de filtragem, reabastecimento e aquecimento. Utilizaram-se 32 peixes por aquário, com peso inicial médio de 30,65 ± 0,50 g. Adotou-se o delineamento inteiramente casualizado caracterizado por cinco níveis de fibra bruta (2,5; 5,0; 7,5; 10,0 e 12,5%) e 5 repetições. Concluiu-se que níveis crescentes de fibra bruta, em dietas purificadas, interferem significativamente na digestibilidade aparente da matéria seca, proteína bruta e do extrato etéreo. Níveis de até 5,00% de fibra bruta não diminuiu a digestibilidade aparente da matéria seca e da proteína bruta e 7,50% de fibra bruta não diminuiu a digestibilidade aparente do extrato etéreo da dieta purificada pela tilápia do Nilo. Entretanto, o aumento do teor de fibra bruta da dieta diminui significativamente o tempo de trânsito gastrintestinal.

Optimum zinc supplementation level in Nile tilapia Oreochromis niloticus juveniles diets

The present study was designed to determine the optimum dietary zinc supplementation to Nile tilapia juveniles (13.3 +/- 1.13 g), by using vegetable-based diets supplemented with increasing levels of zinc from commercial-grade zinc sulfate monohydrate, a previously determined zinc source of higher bioavailability. The basal diet was supplemented with 25, 50, 100, 150, 200, 300, or 400 mg/kg Zn. The experiment was conducted in forty 250-l tanks arranged in a recirculating water system. The experimental period was divided in two phases. For the first 10-week experimental phase, fish were fed satiation diets supplemented with increasing levels of zinc. For the second 5-week experimental phase, fish that were fed diets supplemented with 0-300 mg/kg Zn during the first phase were fed the 400 mg/kg Zn-supplemented diet; fish fed the diet supplemented with 400 mg/kg Zn (first phase) were fed the nonzinc-supplemented diet (second phase). Broken-line analysis showed that the optimum dietary zinc supplementation ((ZnSO4H2O)-H-.) to Nile tilapia juveniles, using weight gain and bone zinc saturation as response criteria, was 44.50 and 79.51 mg/kg Zn, respectively. When challenged by a zinc-deficient diet, tilapia mobilized stored bone zinc to preserve its zinc status. By considering that bone zinc saturation is a more accurate response criterion than weight gain, it was concluded that the optimum dietary zinc supplementation ((ZnSO4H2O)-H-.) in vegetable-based diets to Nile tilapia juveniles is 79.51 mg/kg Zn. (C) 2004 Elsevier B.V. All rights reserved.

Environmental cadmium exposure and metabolic responses of the Nile tilapia, Oreochromis niloticus

The contamination of water by metal compounds is a worldwide environmental problem. This study was undertaken to evaluate the impact of short-term cadmium exposure on metabolic patterns of the freshwater fish Oreochromis niloticus. The fish were exposed to 320, 640, 1280 and 2560 mug/l sublethal concentrations of Cd++ (CdCl2) in water for 7 days. The specific activities of the enzymes phosphofructo kinase (PFK-E.C.2.7.1.11.), lactate dehydrogenase (LDH-E.C.1.1.1.27.) and creatine kinase (CK-E.C.2.7.3.2.) were decreased in white muscle after cadmium treatments, indicating decreases in the capacity of glycolysis in this tissue. Cadmium exposure induced increased glucose concentration in white muscle of fish. on the other hand, cadmium exposure at sublethal concentrations increased phosphofructo kinase and LDH in red muscle of fish. Cadmium significantly decreased total protein concentrations in liver and white muscle regardless of tissue glycogen levels. The data suggest that cadmium acts as a stressor, leading to metabolic alterations similar to those observed in starvation. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

Sex determination studies in two species of teleost fish, Oreochromis niloticus and Leporinus elongatus

Genetic analyses of sex determination have identified sex chromosomes in many teleost fish species. However, there are several cases for which sex ratios do not fit perfectly with the expectations of heterogametic systems, suggesting the influence of either minor sex determining genes or environmental influences on the process of sex differentiation. The frequent absence of sex chromosome markers makes the identification of minor sex-determining genes very difficult. It is easier to test first the hypothesis of environmental sex determination (ESD) by studying the temperature effect, since temperature-dependent sex determination has been demonstrated to occur in several vertebrate groups including 1 fish species. To contribute to a better understanding of fish sex determination, we have tested the effects of high temperatures on sex ratios of Oreochromis niloticus, and have attempted to isolate sex chromosome molecular markers in Leporinus elongatus. Treatments of O. niloticus fry at 36 degrees C applied for 10 days and more, and starting 1 week after fertilization markedly increased the proportion of males, and progeny-testing these males confirmed that some of them are sex-reversed genetic females. Two non-coding sequences of L. elongatus Z and W chromosomes were cloned by genomic subtraction. They cross-hybridized with the genome of a close species without providing sex-specific patterns. A collection of L. elongates individuals was subjected to gonadal and chromosomal sexing, and DNA hybridization with both sequences. These analyses revealed 3 individuals having atypical W chromosomes. Interestingly, 2 of these were males having a ZW karyotype. We assume that these atypical sex chromosome arise by exchanges between Z and W chromosomes, and that a transition between female and male heterogamety is underway in this species.

SYNAPTONEMAL COMPLEX-ANALYSIS IN SPERMATOCYTES OF TILAPIA, OREOCHROMIS-NILOTICUS (PISCES, CICHLIDAE)

Some adaptations of the synaptonemal complex (SC) whole-mounting technique first used in plants permitted its application to meiotic studies in tilapia, Oreochromis niloticus. Direct observation of the chromosome pairing process and bivalent structure during the meiotic prophase of this fish species by light and electron microscopy permitted the analysis of SCs in autosomes and the possible identification of sex chromosomes. The analysis of SCs in spermatocytes of 0. niloticus revealed that all 22 bivalent chromosomes completely paired, except for the occurrence of a size heteromorphism in the terminal region of the largest bivalent associated with the presence of an incompletely paired segment during the synapsis process, which may be the cytological visualization of an XX/XY sex chromosome system in this species.

Mutagenic and genotoxic effects of the Atrazine herbicide in Oreochromis niloticus (Perciformes, Cichlidae) detected by the micronuclei test and the comet assay

Atrazine is the triazinic herbicide most found in the rural aquatic environments due to its extensive use and its stability in such places. The mutagenicity and the genotoxicity of different concentrations of the Atrazine herbicide were determinated by the micronucleus test and the comet assay, using Oreochromis niloticus as test-system. The tested concentrations of Atrazine herbicide were 6.25, 12.5 and 25 mu g/L, both for the micronuclei test and for the comet assay. The results showed a significant rate of micronuclei and nuclear abnormalities for all the tested concentrations of Atrazine herbicide. For the comet assay, we also observed results significantly different from the control in 6.25, 12.5 and 25 mu g/L concentrations. Due to these results, we could infer that such herbicide may be dangerous to the lives of those organisms exposed to it. (c) 2007 Elsevier B.V. All rights reserved.

Relative bioavailability of zinc in supplemental inorganic and organic sources for Nile tilapia Oreochromis niloticus fingerlings

A 90-day feeding experiment was conducted with sex reversed Nile tilapia (Oreochromis niloticus) fingerlings fed purified or practical diets supplemented with different zinc sources to evaluate fish growth performance and zinc and iron retention in fish bones, fillets, liver, skin and eyes. The relative bioavailability value (RBV) of zinc in the supplemental sources tested was also calculated. Fish were fed with isonitrogenous and isoenergetic purified or practical diets supplemented with 150 mg Zn kg -1, as zinc sulphate monohydrate (ZnSO 4), zinc oxide (ZnO) or zinc amino acid complex (Zn-AA). The feeding trial was conducted in 30, 50 L aquaria where four 0.66 ± 0.01 g (mean ± SD) fingerlings were initially stocked. No significant differences were observed for any growth performance variables (P > 0.05). In practical diets, only ZnSO 4 and ZnO presented bone zinc retention similar to that for the standard zinc source. Zinc concentration in the bone of fish fed practical diet supplemented with Zn-AA (171 ± 3.62 μg g -1) was significantly lower than that verified for the practical diets supplemented with the standard zinc source (200 ± 17.7 μg g -1) or with ZnSO 4 (204 ± 19.9 μg g -1). Assuming the concentration of zinc in bones as the response criterion, the supplemental zinc RBV from ZnSO 4 (105%) was higher than the RBV for Zn-AA (95.1%) or ZnO (94.9%). Iron concentration in the bones of animals fed the non-zinc-supplemented purified diet was significantly higher than that observed for purified diet supplemented with Zn-AA (P < 0,05). The results of the present work allowed us to conclude that ZnSO 4 in relation to ZnO or Zn-AA was the supplemental zinc source with higher zinc bioavailability to Nile tilapia. © 2005 Blackwell Publishing Ltd.

Metodologia para quantificação de leucóciotos totais em peixe Oreochromis Niloticus

Haematological investigation is an important part of disease diagnosis. The techniques used for mammals are generally applicable for fishes with slight modification. The presence of nucleated erythrocytes and thrombocytes in fish may cause some confusion in the identification of blood cells, mainly in total leukocytes count. This work evaluated two different methods (direct and indirect) of leukocytes counting. Specimens of tilapia were divided randomly into four groups of 48 fish each. Each group was further randomized into three replicate experiments of 16 fish per replicate in 40 L aquarium and maintained for 10 days. Counting of leukocytes in peripheral blood was determined in six fishes per group at the times: 0, 3, 7 and 10 days. The direct method in Neubauer chamber showed a large dispersion of data in regard to the average, the opposite was observed in indirect method determined in blood smears that showed more homogeneity among groups. Due to this factor the indirect method can be considered more accurate than the direct method for counting leukocytes in fishes.

Policultivo do camarão de água doce Macrobrachium amazonicum (Heller, 1862) com a Tilápia do Nilo (Oreochromis niloticus) alimentadas com rações peletizada e farelada

The objective of this work was to evaluate the influence of fresh water shrimp Macrobrachium amazonicum (Heller, 1862) in performance of Nile tilapia (Oreochromis niloticus) cultivated in polyculture system and feeding with ration pelleted and mashed. The work was realized in Centro de Pesquisa em Aqüicultura Ambiental-CPAA/IAP - Toledo/PR during 37 days. Were utilized like experimental unit 16 ponds excavated, covered with concrete but with bottom of soil with dimension the 4 x 3 m and useful volume the 3,5 m 3. Were utilized 30 tilapias e 150 shrimps for experimental unit distributed at an entirely randomized design with 4 treatments and 4 replications, where TF: tilapia feeding with ration mashed; TCF: tilapia and shrimp feeding with ration mashed; TP: tilapia feeding with ration pelleted; TCP: tilapia and shrimp feeding with ration pelleted. The density used were the 2,6 fishes/m 2 with medium initial weight the 5,58 ± 0,10 g and initial length the 5,56 cm, and the density of shrimp was the 13 shrimps/m 2 with initial length the 1,04 cm. The temperature was gauged daily, while the variables dissolved oxygen, pH and electrical conductivity, weekly. The quantity of ration supplied was the 10% of total biomass of fishes, with feed frequency the 4 times a day, being corrected weekly in function of the biometry. During the experimental period the medium values of temperature, dissolved oxygen, pH and electrical conductivity of the ponds water were 23,42 ± 0,83°C, 5,32 ± 0,52 mg/L, 7,02 ± 0,39, e 100,96 ± 1,81 μS/ cm respectively. Won't registering any influence of shrimp during the cultivation and the ration pelleted provide the better conversion alimentary and performance of tilapias.

Determinação da toxicidade do selênio por meio de análises hematológicas em Oreochromis niloticus

Selenium (Se) is described as an essential micronutrient and participates in different biological functions, as the antioxidant defense systems maintenance and regulation. However, when in high concentrations, Se may cause toxic effects as well as hematological changes in fish. The aim of the present study was to determine the toxicity of selenium in the form of sodium selenate (Na 2Se 6+O 4) in Oreochromis niloticus based on hematological parameters, after exposure to different concentrations (0.01, 0.14 and 1.4 mg Se 6+ L -1). The erythrocytic and leukocytic series were examined over 14 days at intervals of 0, 3, 5, 7,10 and 14 days. The erythrocytic series showed significant alterations in the first 7 days, including the control group. Neutrophils and monocytes showed variations in the first 3 days at a concentration of 1.40 mgSe 6+ L -1 characterizing an acute response. The total number of leukocytes was different in relation to time zero on all Se concentrations. The thrombocyte count also differed statistically from time zero and control in the first 3 days at 0.14 mgSe 6+ L -1. These results indicate that different concentrations induce an acute response with diminution of total leukocytes, neutrophilia, monocytosis and thrombocytosis.

Reproduction, food dynamics and exploitation level of Oreochromis niloticus (Perciformes: Cichlidae) from artisanal fisheries in Barra Bonita Reservoir, Brazil

Nile tilapia (Oreochromis niloticus), which is exotic to South America, is the most common species caught in artisanal fisheries at the Barra Bonita Reservoir, Southeastern Brazil. This species is of great socioeconomic importance for the region and keeps active a population of about 500 fishers. In the present study we assess reproduction, food dynamics and level of exploitation of O. niloticus, caught by artisanal fisheries in the Barra Bonita Reservoir. Specimens were collected monthly, from July 2004-June 2005, and a total of 1 715 specimens were analyzed. Each specimen was examined to obtain biological and biometric data: standard length (cm), total weight (g), reproductive data (sex and stage of maturation), and stomach contents (empty, partly full, and full). We also estimated the sex ratio (by macroscopic observation of gonads), reproductive period (by ovarian development and seasonal average of gonadosomatic index in females), and feeding habits (by stomach contents). The possible relationship between abiotic factors and the reproductive period was statistically verified using Spearman's Rank Correlation. The FiSAT (ELEFAN I) package was used to assess growth parameters, mortality rates and to infer exploitation rate from standard length frequencies. The O. niloticus population had a sex ratio of 1.3:1 (M:F). Results indicated that ripe females were captured throughout the year, with a higher frequency during the winter-2004 (with a frequency of 59%, at a mean temperature of 20.5°C), and in spring-2004 (with a frequency of 60.5% at a mean temperature of 21.18°C). The GSI mean values obtained by season were: winter-2004: 1.71; spring-2004: 1.72; summer-2005: 0.80, and autumn-2005: 1.19. The Spearman correlation indicated positive values with respect to pH, dissolved oxygen, electric conductivity, transparency and chlorophyll a, and negative values with respect to temperature, accumulated rainfall and altimetric benchmark. The main food items were phytoplankton and periphytic algae, observed in 99.6% of the analyzed stomachs. The estimated growth and mortality parameters were: L∞=33.60cm, k=0.63/year, longevity= 4.76years, Z=2.81/ year, M=1.20/year and F=1.61/year. The weight-length relationship was Ln Wt=-2.8532+2.8835 Ln Lp. The estimated yield per recruit values were as follows: E=0.570, Emax=0.776, E0.1=0.604 and E0.5=0.349. These results indicate that a well established population of O. niloticus is present at Barra Bonita Reservoir; with an active reproduction throughout the year, more intense during winter and spring, and that O. niloticus is a phytoplanktophagus species. There were no indications that this species is being overfished, we therefore recommend that, due to its exotic condition, no restrictions need to be taken on its fishing activities.