The fish embryonic development comprises the events between the egg fertilization up to larvae hatching, being useful for the identification of viable eggs in productivity and survival studies as well as in raising experiments of several species. The goal of the present study was to characterize the embryonic development of Pimelodus maculatus (Siluriformes; Pimelodidae). The embryogenesis was typical of teleosteans, but with differences in relation to other species such as duration of development, type of blastocoel, moment of somite segmentation among others. Six stages of embryonic development were defined: zygote, cleavage, blastula, gastrula, organogenesis (divided in phases: early segmentation and late segmentation) and hatching with a period of incubation equal to 13 hours at 29 ºC and 17 hours at 25 ºC. The extruded oocytes presented a mean diameter of 812 m before and 1066 m after hydration. When fertilized, they presented a yellowish coloration and a gelatinous layer surrounding the chorion. The cleavage pattern is described as: 2; 4; 8 (4x2); 16 (4x4); 32 (4x8) and 64 (2x4x8) blastomeres up to morula phase (+64 cells). It was also possible to observe at this phase, the beginning of the formation of the yolk syncyctial layer (YSL). Afterwards, the blastula and gastrula stages followed. The end of gastrula was characterized by the formation of the yolk plug. Subsequently, the differentiation between cephalic and caudal regions began, along with the embryo elongation, structuring of optic, Kupffer's and otic vesicles besides a previously unidentified structure in the yolk syncyctial layer. The end of this stage is typified by the tail detachment. The late segmentation phase was distinguished by a free tail, presence of more than 30 somites, optic and otic vesicles, development of posterior intestine, pigmentation of cephalic and caudal regions of yolk sac and embryo growth. The recently-hatched larvae presented a primordial digestive tract, quite evident and pigmented eyes, closed mouth, encephalic vesicles and a mean length of 3410 m. O desenvolvimento embrionário de peixes compreende eventos que ocorrem desde o ovo fertilizado à eclosão das larvas, podendo auxiliar na identificação dos ovos viáveis em estudos de produtividade e sobrevivência, como também nas pesquisas de cultivo desses animais. O objetivo do presente estudo foi caracterizar o desenvolvimento embrionário do Pimelodus maculatus (Siluriformes; Pimelodidae). A embriogênese foi característica de teleósteos, apresentando variações que difere de outras espécies como, tempo de desenvolvimento, tipo da blastocele, momento de segmentação dos somitos, entre outros. Seis estágios de desenvolvimento embrionário foram definidos: zigoto, clivagem, blástula, gástrula, organogênese (dividido em fases: segmentação inicial e segmentação final) e eclosão com período de incubação de 13 horas à 29ºC e de 17 horas à 25ºC. Os ovócitos extrusados apresentaram diâmetro médio de 812 m antes da hidratação e após 1066 m. Após a fertilização, apresentaram colo...

SummaryThe embryogenesis of Brycon cephalus was established in seven stages: zygote, cleavage, blastula, gastrula, segmentation, larval and hatching, in an incubation period of 11 h (26 • C). The zygote phase was observed directly after fertilization and egg hydration. Cleavage began at 0.5 h of incubation and extended up to the morula phase (1.5 h; +100 blastomeres). Cleavage was meroblastic and underwent the following division pattern: the first five divisions were vertical and perpendicular to each other, following the model 2 × 2, 4 × 2, 4 × 4 and 4 × 8. The sixth division was horizontal and occurred at 1.25 h after fertilization, giving rise to two cell layers (4 × 8 × 2) with 64 blastomeres. At the blastula stage (1.25-1.5 h), an irregular space between the blastomeres, the blastocoele, could be detected and the periblast structure initiated. The gastrula (1.75-6.0 h) was characterized by the morphogenetic movements of epiboly, convergence and cell involution, and formation of the embryonic axis. The segmentation stage (7-9 h) comprised the development of somites, the notochord, optic, otic and Kupffer's vesicles, neural tube, primitive intestine and ended with the release of the tail. The larval stage (up to 10 h) was characterized by the presence of 30 somites and growth and elongation of the larvae. At the hatching stage, the embryos presented more than 30 somites and exhibited swimming movements and a soft chorion. The blastomeres presented euchromatic nuclei, indicating a high mitotic activity and many yolk globules in the cytoplasm. The periblast was constituted of a layer with several nuclei and many vesicles, which grew during the epiboly movement.

Several investigations have been carried out to improve the productivity of tambaqui, an economically important fish species in Brazil and other Latin American countries. This study determined the digestible protein (DP) requirements in juvenile tambaqui by assessing their productive performance and nutritional efficiency. It also evaluated the effects of different dietary DP levels on the morphology and cellularity of skeletal fast muscle fibres. The 1750 tambaqui tested (6.53 ± 0.43 g body weight, 7.58 ± 0.18 cm length) were randomly distributed into 35 tanks. Fish were fed one of the seven isocaloric diets, which contained 140, 170, 200, 230, 260, 290 or 320 g/kg DP. The DP requirement, calculated by segmented (broken line) regression of weight gain data, was 290 g/kg. An increase in diet DP to 290 g/kg significantly improved final weight, weight gain, feed intake, specific growth rate and crude protein gain, and changed fibre diameter in deep muscle. Muscle fibres were randomly distributed into a mosaic pattern, characterized by fibres with different diameters. Treatments with 290 and 320 g/kg DP increased the frequency of large‐diameter fibres (>50 µm), indicating hypertrophic growth of skeletal muscle during the juvenile phase, which occurred in conjunction with hyperplasia.

No abstract

This study evaluated the apparent digestibility coefficients (ADC) of essential (EAA) and non-essential (NEAA) amino acids of 13 ingredients for tambaqui (Colossoma macropomum) diets. Proteic and energetic ingredients were analyzed separately. The trial with energetic and proteic ingredients were arranged in a randomized block design, with four replicates: energetic ingredients (corn, wheat bran, broken rice, and sorghum) with four treatments, whereas proteic ingredients (corn gluten meal, soybean meal, poultry byproduct meal, salmon meal, fish meal [tilapia processing residue], wheat gluten meal, feather meal, cottonseed meal, and alcohol yeast [spray dried]) with nine treatments. Each block was considered as one round of fecal collection. A total of 420 tambaqui juveniles (mean initial weight: 70±8.58 g) were used. Among energetic ingredients, corn (94.6%) and wheat bran (91.9%) had the highest ADCEAA, followed by broken rice (75.7%), and sorghum (72.8%). On average, ADCEAA and ADCNEAA values of proteic ingredients were 79.5-98.5%, except for alcohol yeast (ADCEAA: 68.4 and ADCNEAA: 76.7%). Tryptophan was the first limiting amino acid in most ingredients tested and had the lowest chemical scores (0.06-0.51), except for wheat bran, corn gluten meal, and soybean meal, in which lysine was the first limiting amino acid. Soybean meal had the highest digestible essential amino acid index (EAAI: 1.02) and the most balanced amino acid profile, whereas wheat gluten meal had the lowest EAAI (0.48). Overall, tambaqui was very efficient to digest proteic and energetic ingredients.

A qualidade da dieta pode ser avaliada quantificando a habilidade dos peixes para digerir os alimentos. Portanto, este estudo teve como objetivo determinar os coeficientes de digestibilidade aparente (CDA) para proteína bruta (PB), extrato etéreo (EE) e energia bruta (EB) de nove ingredientes proteicos e sete ingredientes energéticos mais comumente usados em dietas comerciais para tambaqui. No total, 510 juvenis de tambaqui foram alimentados com dietas-teste contendo uma dieta de referência suplementada com um marcador de digestibilidade inerte (Cr2O3). As análises de digestibilidade mostraram que o glúten de milho apresentou o CDAPB(98,09%) e CDAEB (96,91%) mais alto, enquanto que a levedura de álcool apresentou o menor CDAPB (63,17%) e CDAEB (46,24%). Os ingredientes proteicos foram revelados como excelentes fontes de lipídios (CDAEE > 85,0%), com exceção do glúten de trigo (CDAEE: 63,73%). O milho (94,5%) e o farelo de trigo (86,08%) apresentaram o CDAPB mais alto de todos os ingredientes energéticos. Não foram observadas diferenças significativas no CDAEE dos ingredientes energéticos testados. Dos ingredientes energéticos testados, o óleo de milho (95,7%), óleo de peixe (93,61%), o óleo de soja (93,31%) e o milho (88,70%) apresentaram o CDAEB mais alto. O uso de ingredientes proteicos e energéticos com altos coeficientes de digestibilidade, como os relatados, pode orientar a formulação de dietas de alta qualidade para tambaqui.

This study evaluated the application of stable isotopes of carbon as an alternative and more accurate method to determine gastrointestinal transit time (GTT) in fish by comparing it to the inert marker method. The stable isotope method detects alterations of the normal carbon flow in a biological system by analyzing naturally occurring isotopes of carbon, contrary to studies based on conventional techniques that apply external markers to the diet to determine GTT through visual observation of the color change in feces. Therefore, 320 pacu, Piaractus mesopotamicus juveniles were reared in 32 tanks under two different temperatures (25 and 29 C). The pacu juveniles received two different diets, one based on ingredients derived from C3 photosynthetic cycle plants and the other based on C4 plant ingredients, both containing titanium oxide (TiO2) as a marker. After 40 d, the isotopic signature of the diets was changed, and the marker was replaced by chromic oxide (Cr2O3). In the isotopic technique, the feces were analyzed to determine the exchange in the isotopic ratio of carbon δ13C. Both methods found that GTT was faster (nearly 6 h) in fish at 29 C when using the C4/C3 feeding strategy and slower in fish at 25 C using the C3/C4 strategy (15 h by inert marker and 18 h by the isotopic method). In conclusion, GTT determination in pacu juveniles using the stable isotope technique exhibits the same accuracy obtained with the inert marker method at temperatures suitable (nearly 29 C) for the metabolism of these animals.

Resumo -O objetivo deste trabalho foi avaliar o desempenho e a sanidade da estrutura hepática de tilápia-do-nilo, masculinizada hormonalmente ou não masculinizada, criada em tanques-rede com dois níveis proteicos. Tilápias-do-nilo da linhagem Tailandesa (total de 2.400), com peso médio inicial de 127 g, foram distribuídas em delineamento inteiramente casualizado, com quatro tratamentos, em arranjo fatorial 2×2, correspondente aos grupos de tilápias masculinizadas hormonalmente ou não masculinizadas e ao teor proteico na dieta de 28 ou 32% de proteína bruta, com três repetições. Após 115 dias de alimentação, não houve interação entre os fatores quanto a peso final, ganho de peso, conversão alimentar, comprimento final e sobrevivência. Não houve diferença entre os peixes masculinizados hormonalmente e os não masculinizados, quanto a peso final, ganho de peso e sobrevivência, o que mostra a possibilidade de sua produção em tanques-rede, sem a necessidade de masculinização hormonal. A proteína bruta a 32% na dieta possibita melhor desempenho para ambos os grupos. Alterações histológicas no fígado -como o incremento do volume das células, o desarranjo da disposição cordonal e o aumento de vesículas nos hepatócitos -são encontradas nos peixes masculinizados hormonalmente e são mais acentuadas nos peixes alimentados com 32% de proteína bruta na dieta.Termos para indexação: Oreochromis niloticus, proteína, reversão sexual, sanidade hepática. Hepatic histology and cage production of Nile tilapia hormonally masculinized or nonmasculininizedAbstract -The aim of this work was to evaluate the performance and the liver structure health of Nile tilapia hormonally masculinized or nonmasculinized, reared in cages with two protein levels. Two groups of Nile tilapia of Thai lineage (total 2,400), with 127 g initial average weight, were distributed in a completely randomized design with four treatments, in a 2x2 factorial arrangement, corresponding to the groups of hormonally masculinized or nonmasculinized fish, and to diet protein level of 28 or 32% of crude protein, with three replicates. After 115 days feeding, there was no interaction between the factors for final weight, weight gain, feed conversion rate, final length and survival. There was no difference between hormonally masculinized and nonmasculinized fish for final weight, weight gain, and survival, which shows the possibility of their production in cages, without the need of hormonal masculinization. Crude protein at 32% in the diet enables a better performance for both groups. Histological changes in the liver -such as increased cell volume, disruption of the cord-like arrangements, and increase of vesicles in the hepatocytes -are found in hormonally masculinized fish, and are more pronounced in fish fed 32% crude protein in the diet.