This study aimed to evaluate the effect of oregano oil on the intestinal and liver morphometry of yellow tail tetra, Astyanax altiparanae. Fish (1.46 ± 0.09 g) were kept in a 60-L aquaria, at a stocking density of 0.5 fi sh L -1 . Six diets containing varying amounts of oregano oil were evaluated (0.0; 0.5; 1.0; 1.5; 2.0 and 2.5 g of oregano oil kg -1 ). At the end of 90 days, the fi sh were euthanised. Four intestines and four livers were collected per treatment, which were fi xed in Bouin and embedded in resin. For height and width folds, the absorption surface area and thickness of the muscular layer a positive linear effect of oregano oil was observed. A decrescent linear effect on the total number of goblet cells was also observed. For the cytoplasmic percentage of hepatocytes and liver glycogen, a positive linear effect of oregano oil was observed. There was a decreasing linear effect on the percentage of nuclei in the hepatocytes and capillaries. Thus, the oregano essential oil promotes increased absorption areas, modulates the amount of goblet cells involved in protecting the intestinal mucosa and promotes cytoplasmic increase with greater deposition of liver glycogen in yellow tail tetra.

Neste estudo, avaliaram-se as exigências nutricionais de proteína para alevinos de acará-bandeira. O delineamento experimental utilizado foi o inteiramente casualizado, com quatro tratamentos (34, 38, 42 e 46% de PB) e quatro repetições. Alevinos (0,44 ± 0,05 g) foram distribuídos em 16 aquários com volume individual de 25 L, dotados de sistema de filtragem, aeração e controle de temperatura (26 ± 0,5ºC), em densidade de estocagem de seis peixes/aquário, onde foram alimentados à vontade, às 8, 11, 14 e 17 h, durante 60 dias. Os parâmetros de desempenho produtivo avaliados foram: peso final, ganho de peso, consumo de ração, conversão alimentar, taxa de crescimento específico e taxa de eficiência protéica (TEP). Ao final do experimento, não foi observado efeito significativo dos tratamentos sobre o desempenho produtivo, exceto para a TEP. A dieta com 46% de PB resultou em TEP significativamente menor que as dietas com 34 e 38% PB, enquanto a dieta com 42% de PB não diferiu das demais. Dietas contendo 34% de PB atendem às exigências nutricionais em proteína de alevinos de acará-bandeira.

The contribution of growth and turnover to the muscle delta(13)C change process was investigated using mathematical models which associate delta(13)C change to time of intake of a new diet or increase in body mass. Two groups of Nile tilapia (Oreochromis niloticus) were fed on diets based on C3 (delta(13)C=-25.64+/-0.06 per thousand) or C4 (delta(13)C=-16.01+/-0.06 per thousand) photosynthetic cycle plants to standardize the muscle delta(13)C. After establishing the carbon isotopic equilibrium, fish (mean mass 24.12+/-6.79 g) then received the other treatment diet until a new carbon isotopic equilibrium could be established, characterizing T1 (C3-C4) and T2 (C4-C3) treatments. No significant differences were observed in fish productive performance. Good fits were obtained for the models that associated the delta(13)C change to time, resulting in carbon half-life values of 23.33 days for T1 and 25.96 days for T2. Based on values found for the muscle delta(13)C change rate from growth (0.0263 day(-1) and 0.0254 day(-1)) and turnover (0.0034 day(-1) and 0.0013 day(-1)), our results indicate that most of the delta(13)C change could be attributed to growth. The application of model that associated the delta(13)C change to body mass increase seems to produce results with no apparent biological explanation. The delta(13)C change rate could directly reflect the daily ration and growth rate, and consequently the isotopic change rates of carbon and other tissue elements can be properly used to assess different factors that may interfere in nutrient utilization and growth.

The effects of grain-based diets from C3 or C4-cycle plants on muscle delta(13)C change process in Nile tilapia (Oreochromis niloticus) fingerlings were investigated. Two groups of sex reversal males Nile tilapia fingerlings were fed with isoproteic (32.0% DP) and isocaloric (3200 kcal DE/kg) diets, differing from each other by their delta(13)C. Muscle samples were collected and the carbon isotopic composition was measured. For C4 diet, the formula for the muscle delta(13)C change related to the intake time of a new diet was delta(13)C=-14.88-9.21e(-0.0209t) and the half-life (T) of the muscle carbon was 33.2 days. For C3 diet, the formula was delta(13)C=-25.43+8.59e(-0.0533t) with T=13 days. The C3 diet was considered more appropriate based on its palatability and consequent larger food intake than the C4 diet, resulting in an increased muscle delta(13)C change rate. However, for future studies, would be necessary to mix both the C3 and C4 feedstuffs to formulate diets nutritionally appropriated, with contrasting stable isotopes signatures. Tissue delta(13)C change rate is therefore indicated as a promising tool to better understand the biotic and abiotic factors that influence nutrients utilization from the diet and animal growth.

No abstract

Acute and chronic salinity tolerance in adult siamese fighting fish, Betta splendensABSTRACT -Salinity tolerance of Betta splendens was evaluated in a complete randomized design, with six salt concentrations in the water (0; 3; 6; 9; 12 and 15 g common salt/L) with five replications (1 fish/replication). Adult female B. splendens were individually placed in aquariums in an incubation chamber at 26 ± 0.2ºC and 12-hour photoperiod. Fish were fed to satiation, once a day, with commercial diet. Feed intake and survival rate were measured every 12 hours. To evaluate the effect of acute salinity, the mean survival time and median lethal salinity-96 h were calculated, while the chronic effect (18 days) was assessed by calculating the survival salinity maximum and median lethal salinity. The mean survival time was significantly lower at 15 g/L water salinity. The median lethal salinity-96 h calculated was 11.88 g/L, the survival salinity maximum was between 6 and 7 g/L, and the median lethal salinity was 9.35 g/L. There was a significant interaction between feeding time and water salinity. Considering that the B. splendens is a freshwater species, it was concluded that this species demonstrated a high tolerance to water salinity.

O potencial genético para o crescimento de qualquer espécie animal depende das condições ambientais em que são cultivados, como competição por espaço, alimentos e oxigênio. O presente experimento foi conduzido com o objetivo de avaliar o desempenho produtivo de alevinos de tricogaster (Trichogaster trichopterus), uma espécie de peixe ornamental, submetidos a diferentes densidades de estocagem e índices alimentares. Os peixes (com peso médio de 0,56 g ± 0,09 e 0,96 g ± 0,13) foram divididos em dois blocos, submetidos às densidades de 5, 10 e 15 peixes/aquário e alimentados a taxas de 3, 6 e 9% do peso vivo/dia. Os peixes foram alimentados, uma vez ao dia, com ração comercial moída e mantidos em aquários (com capacidade para 100 L) dotados de filtro biológico e aeração, com renovação parcial da água. Os parâmetros físico-químicos da água mantiveram-se dentro da faixa de conforto para a espécie, com diminuição do pH e da condutividade no final do período experimental, para a maior densidade (15 peixes/aquário) e índice alimentar mais elevado (9% p.v./dia). A taxa de arraçoamento afetou significativamente o comprimento final, peso final, ganho de peso, a taxa de crescimento específico e o fator de condição. Os peixes alimentados à base de 9% p.v./dia apresentaram os melhores resultados. Para as diferentes densidades de estocagem, apenas o fator de condição apresentou diferença significativa, com os melhores resultados para os peixes cultivados à densidade de 10 peixes/aquário, em relação aos cultivados à densidade de 15 peixes/aquário. Não foram observadas interações significativas entre os índices alimentares e as densidades de estocagem.

This study aimed to evaluate the effect of different proportions of soybean and linseed oil to replace fish oil in diets for female lambari (Astyanax altiparanae). A completely randomized design with seven treatments and five replicates was used. The treatments consisted of a diet containing fish oil and six diets containing different proportions of soybean oil (S) and linseed oil (L), 10S/0L, 8S/2L, 6S/4L, 4S/6L, 2S/8L and 0S/10L. The fish that received the highest proportion of linseed oil (0S/10L) had the lowest crude lipid in their carcasses. The highest linolenic acid (18:3n3) concentrations were detected in the carcasses of fish fed diets with high proportions of linseed oil (4S/6L, 2S/8L, and 0S/10L). The highest n6/n3 ratios corresponded to the carcasses of fish fed diets containing the lowest proportions of linseed oil (10S/0L and 8S/2L). The highest levels of 20:5n3 (eicosapentaenoic acid [EPA]), 22:6n3 (docosahexaenoic acid [DHA]) and EPA+DHA occurred in fish fed diets containing fish oil. Among the fish that received diets with vegetable oils, the EPA+DHA was higher in the fish of the treatments 4S/6L, 2S/8L and 0S/10L. Diets supplemented with a 4S/6L proportion provide adequate deposition of the n3 fatty acids series in the lambari carcass.