In vertebrates, the essential fatty acids (FA) that satisfy the dietary requirements for a given species depend upon its desaturation and elongation capabilities to convert the C18 polyunsaturated fatty acids (PUFA), namely linoleic acid (LA, and α-linolenic acid (ALA, 18:3n-3), into the biologically active long-chain (C20-24) polyunsaturated fatty acids (LC-PUFA), including arachidonic acid (ARA, 20:4n-6), eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3). Recent studies have established that tambaqui (Colossoma macropomum), an important aquaculture-produced species in Brazil, is a herbivorous fish that can fulfil its essential FA requirements with dietary provision C18 PUFA LA and ALA, although the molecular mechanisms underpinning such ability remained unclear. The present study aimed at cloning and functionally characterizing genes encoding key desaturase and elongase enzymes, namely fads2, elovl5 and elovl2, involved in the LC-PUFA biosynthetic pathways in tambaqui.First, a fads2-like desaturase was isolated from tambaqui. When expressed in yeast, the tambaqui Fads2 showed Δ6, Δ5 and Δ8 desaturase capacities within the same enzyme, enabling all desaturation reactions required for ARA, EPA and DHA biosynthesis.Moreover, tambaqui possesses two elongases that are bona fide orthologs of elovl5 and elovl2. Their functional characterization confirmed that they can operate towards a variety of PUFA substrates with chain lengths ranging from 18 to 22 carbons. Overall our results provide compelling evidence that demonstrates that all the desaturase and elongase activities required to convert LA and ALA into ARA, EPA and DHA are present in tambaqui within the three genes studied herein, i.e. fads2, elovl5 and elovl2.

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RESUMO -Este experimento foi conduzido com o objetivo de avaliar o condicionamento alimentar de alevinos de trairão (Hoplias cf. lacerdae). Foram utilizados seis aquários com capacidade para 20 litros cada, dotados de sistema artificial de aeração, temperatura controlada (27±0,5 o C), cobertos com lona plástica preta, mantendo o ambiente interno escuro todo o tempo (0L:24E), sendo descobertos apenas para os manejos diários. Alevinos de 2,9±0,2 cm de comprimento foram estocados a uma densidade de 4 animais/L e submetidos aos seguintes tratamentos: aceitação direta de dietas artificiais e condicionamento alimentar por meio da substituição da ração semi-úmida por ração seca. Ao final do experimento, foram obtidas taxas médias de sobrevivência de 27,50 e 96,66% para o primeiro tratamento e segundo tratamentos, respectivamente, evidenciando que o condicionamento alimentar é um manejo eficiente na produção e sobrevivência de alevinos de trairão.Palavras-chave: condicionamento alimentar, dietas artificiais, Hoplias cf. lacerdae, trairão Training Strategies Trairao Fingerlings (Hoplias cf. lacerdae)ABSTRACT -An evaluation of training strategies in fingerlings of trairao was carried out. The experimental design included six 20 L tanks with artificial aeration, controlled temperature variation (27±0.5°C), and continuously darkened (0L:24D), except during daily management. Fingerlings with 2.9±0.2 cm long were kept at a 4 specimens/L and they were allotted to the following treatments: the first was direct offering of artificial diet and the second involved training strategies by means of the replacement of semi humid food for dry food. At the end of the experiment, average survival rates were 27.5 and 96.66% for the first and second treatments, respectively, demonstrating that feeding conditioning is an efficient management in production and survival of Hoplias cf. lacerdae fingerlings. . Zootec., v.31, n.5, p.1881-1885, 2002 Introdução O trairão (Hoplias cf. lacerdae), espécie carnívora, apresenta carne de excelente qualidade, podendo ser comparada com a de muitos peixes nobres brasileiros, tendo grande aceitação por parte da população; além disso, apresenta características desejáveis para a pesca esportiva, devido a sua agressividade. Estas caracterís-ticas evidenciam o grande potencial desta espécie para a piscicultura nacional. Entretanto, muitos obstáculos vêm sendo encontrados em relação à criação em larga escala dessa espécie para atender a demanda do mercado consumidor, como dificuldade na aquisição de matrizes de qualidade e no manejo alimentar tanto dos adultos quanto dos alevinos; altos custos de manutenção de reprodutores; falta de estruturas e tecnologia adequada; e pouco conhecimento da biologia dessa espécie. R. BrasPara solucionar parte desses obstáculos, visando o desenvolvimento de criação de espécies carnívoras dentro do cenário da aqüicultura nacional, vários pesquisadores e empresas têm investido esforços na busca de tecnologia para a produção intensiva desses peixes (Campos, 1998;Machado et al., 1998...

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.

RESUMO -Neste trabalho foi avaliado o efeito da utilização de três rações comerciais indicadas para alimentação de peixes carnívoros sobre os rendimentos do processamento e a composição de filés de surubim (Pseudoplatystoma sp) cultivados em tanques-rede. Os surubins foram cultivados em tanques-rede durante um ano, período em que foram alimentados com três rações contendo 43,5; 42,6 e 42,1% de proteína bruta; 6,3; 8,7 e 4,5% de extrato etéreo e 5.078; 4.931 e 4.994 kcal de energia bruta, respectivamente, em um delineamento inteiramente casualizado, com três tratamentos e três repetições. Em cada tanque, foram selecionados cinco peixes com pesos entre 1.280 e 1.340 g, que foram insensibilizados e sacrificados para determinação dos rendimentos de carcaça com e sem pele, cabeça, filé total, lateral e abdominal, fígado, pele e esqueleto. Amostras de filés laterais e abdominais foram tomadas para análises bromatológicas. Foram avaliados 22 fêmeas e 23 machos, no entanto, não foi observada diferença entre os sexos quanto aos principais rendimentos de processamento. Os rendimentos de filé abdominal e de resíduos com e sem pele diferiram entre as rações. A composição bromatológica dos filés (lateral e abdominal) não foi influenciada pelas rações e não diferiu entre os cortes. A utilização de rações comerciais no cultivo não acarretou mudanças na quantidade e na qualidade dos principais cortes do surubim.Palavras-chave: processamento, Pseudoplatystoma, rendimento, surubim, tanque-rede Processing yield and chemical composition of fillets of surubim reared in net cagesABSTRACT -The objective of this work was to evaluate the effect of three commercial feeds recommended for carnivorous fish on processing yield and fillet composition of surubim (Pseudoplatystoma sp) raised in net cages. The surubim fishes were raised in net cages during one year, when were fed three diets with 43.5, 42.6, and 42.1% crude protein; 6.3, 8.7, and 4.5% ether extract and 5,078, 4,931, and 4,994 kcal of gross energy, respectively. Fishes were allotted to a completely randomized design, with three treatments and three replicates. Five surubim fishes weighing from 1280 to 1340g were selected from each cage and unsensibilized and slaughtered for posterior determination of the processing yields of carcass with and without skin, head, total fillet, lateral and abdominal fillets, liver, skin and skeleton. Samples of lateral and abdominal fillets were colleted to determine their chemical analyses. No differences were observed between sexes for the principal processing yields, in a total of 22 females and 23 males. There was difference in the abdominal fillet and of the residues with and without skin among diets. There was difference in the abdominal fillet and of the residues with and without skin among diets. The use of different commercial diets during the raising period did not affect the amount and quality of principal edible cuts of surubim fish.Key Words: cage, dressing out, Pseudoplatystoma, surubim, yield IntroduçãoA busca por produtos de fácil pr...

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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.