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- Recent advances in nutrition of fish larval | Avanços recentes em nutrição de larvas de peixesPublication . Conceição, L. E. C.; Aragão, C.; Richard, Nadège; Engrola, S.; Gavaia, Paulo J.; Mira, Sara; Dias, J.Os requisitos nutricionais de larvas de peixes são ainda mal compreendidos, o que leva a altas mortalidades e problemas de qualidade no seu cultivo. Este trabalho pretende fazer uma revisão de novas metodologias de investigação, tais como estudos com marcadores, genómica populacional, programação nutricional, génomica e proteómica funcionais, e fornecer ainda alguns exemplos das utilizações presentes e perspectivas futuras em estudos de nutrição de larvas de peixes.
- Improving weaning strategies for Senegalese sole: effects of body weight and digestive capacityPublication . Engrola, S.; Conceição, L. E. C.; Dias, L.; Pereira, R.; Ribeiro, Laura; Dinis, Maria TeresaTo optimize Senegalese sole-weaning strategies, three experiments were performed.The first trial tested four weaning strategies with a10mg sole. Artemia-fed sole grew threefold less than fish fed an inert diet. Sudden weaning (abrupt change from Artemia to inert diet) and weaning with co-feeding produced larger sole than did a late weaning treatment; delayed weaning negatively affected ¢sh growth. In the second experiment, the digestive capacity of early-weaned 1, 2 and 4mg sole was investigated. The highest growth was observed in sole weaned at 4mg. Digestive enzyme pro¢les suggest that sole have an adaptation period to inert diets, with reduced feed intake. This adaptation period is inversely proportional to post-larvae weight. The third experiment examined weaning with cofeeding at di¡erent weights (2,5 and11mg).These studies demonstrate that sole of 5^10mg can be weaned, with high survival rates. On the basis of the digestive enzyme pro¢les, the early introductionof inert diets in co-feeding with Artemia seems to affect intestinal processes in smaller postlarvae. This study also suggests that trypsin and alkaline phosphatase may be used as indicators of nutritional status in sole ofo5mg.
- Co-feeding of inert diet from mouth opening does not impair protein utilization by Senegalese sole (Solea senegalensis) larvaePublication . Engrola, S.; Mai, M.; Dinis, Maria Teresa; Conceição, L. E. C.In most marine species inert diets alone have a poor ability to sustain fish larvae growth and development. Furthermore, results of co-feeding inert diets and live prey are variable, which may be related to the effect of inert diets on digestive maturation and subsequently protein utilization. The aim of the present work was to investigate how different feeding regimes, live feed alone or co-fed with an inert diet, influence protein utilization in Senegalese sole larvae. Feed intake, protein absorption, protein retention and protein catabolism were estimated in sole from 8 to 35 days after hatching (DAH), using 14C-labelled Artemia protein and posterior incubation in metabolic chambers. Postlarvae that were co-fed with an inert diet from mouth opening ate more than postlarvae fed Artemia alone at most sampling ages. Sole Artemia protein digestibility ranged from 56.97 (16 DAH) to 81.32% (22 DAH). Sole larvae that were fed a second meal had a slightly, though significant, higher digestibility than sole fed a single meal. Digestibility was lower in co-fed sole during metamorphosis climax, and similar between treatments at other developmental stages. Retention efficiency remained almost constant during early development, and was not affected by feeding regime. In short, co-feeding of an inert diet from mouth opening does not impair protein utilization by Senegalese sole larvae.
- Skeletal evaluation and technical improvements to decrease the incidence of skeletal deformities in Solea senegalensis, KaupPublication . Gavaia, Paulo J.; Richard, Nadège; Dâmaso, L.; Dinis, Maria Teresa; Pousão-Ferreira, P.; Engrola, S.; Conceição, L. E. C.; Cancela, LeonorThe appearance of skeletal deformities is a major problem associated to intensive, large-scale culture of fish species, affecting growth, development and ultimately, survival of produced fish. Although the mechanisms working behind it are still unclear, it is known that environmental, genetic and nutritional factors play fundamental roles. Given its importance as a vertebrate model to study skeleton-related diseases, the selection of an appropriate dietary protocol is a critical step in order to diminish the nutritional effect on bone and cartilage development. To better understand the effect of diet on skeletal development and deformities, as well as on larvae and juvenile global performance, we have tested four distinct dietary regimes, composed of rotifers Brachionus sp., Artemia nauplii and dry, formulated food.
- Comparing skeletal development of wild and hatchery-reared Senegalese sole (Solea senegalensis, Kaup 1858): Evaluation in larval and postlarval stagesPublication . Gavaia, Paulo J.; Domingues, S.; Engrola, S.; Drake, P.; Sarasquete, C.; Dinis, Maria Teresa; Cancela, LeonorThe Senegalese sole is a marine pleuronectiform that naturally occurs in Southern Europe and Mediterranean region where it is being produced in aquaculture, in particular in Portugal and Spain. The aim of this study was to assess the quality of hatchery-reared larvae in comparison with those reared in the wild, and determine to which extension wild growing larvae are also affected by skeletal deformities. The main structures affected included those forming the axial skeleton, the caudal fin complex and both anal and dorsal fins, with the most prevalent anomalies affecting caudal vertebrae and arches. Hatchery-reared fish presented a higher incidence of deformities (79%) compared with the 19% observed in wild specimens. In wild postlarvae collected in Autumn no deformities were observed. This work clearly shows that wild Senegalese sole present less skeletal deformities than those hatchery-reared during larval stages, indicating a selective mortality of wild deformed fish and/or an effect of aquaculture-related rearing conditions in the development of skeletal deformities in sole.
- Hormonal induction of Atlantic dusky grouper (Epinephelus marginatus) broodstockPublication . Conceição, L. E. C.; Cabrita, Elsa; Engrola, S.; Lacuisse, M.; Pousão-Ferreira, P.; Dinis, Maria TeresaImmature fish and young females were sex reversed using hormonal induction in two consecutive years. In the first year one permanent male was obtained. Collected sperm of both years ranges from 30 μl to 300 μl and cell concentration varies from 3 to 6.5 x109 spermatozoa/ml. Atlantic dusky grouper can successfully be induced to functional males with 17α-methyltestosterone implants.
- Nutritional physiology during development of Senegalese sole (Solea senegalensis)Publication . Conceição, L. E. C.; Ribeiro, Laura; Engrola, S.; Aragão, C.; Morais, S.; Lacuisse, M.; Soares, Florbela; Dinis, Maria TeresaThe Senegalese sole, a species with a complex metamorphosis, difficulties in weaning and with occasional problems of malpigmentation and skeletal deformities, is a good model species to study larval nutritional physiology. In addition, the early metamorphosis and acquisition of a peculiar non-proactive bottom-feeding behaviour make early weaning an important issue in sole hatcheries. The present work reviews recent findings in different aspects of nutritional physiology during the development of Senegalese sole, in an attempt to optimize the composition of sole diets and to understand what are the limiting factors for weaning sole. Both digestive enzymes activity and tracer studies using 14C-Artemia show that sole larvae, even at young stages, have a high capacity for digesting live preys. This is reflected in a high growth potential and low mortality rates for this species during the larval stage compared to other marine fish species. Based on the observation of the digestive enzymes profile, early introduction of inert microdiets in co-feeding with Artemia does not seem to affect intestinal function. However, when co-feeding is not provided, intestinal activity may be depressed. Furthermore, early introduction of microdiets in co-feeding with Artemia may have a positive effect on survival rates, but at the expense of lower growth rates and higher size dispersal. This may reflect variation in the adaptation capacity of individual larvae to inert diets. High dietary neutral lipid (soybean oil) content results in reduced growth and accumulation of lipid droplets in the enterocytes and affects the capacity of Senegalese sole larvae to absorb and metabolise dietary fatty acids (FA) and amino acids (AA). Through tube feeding of different 14C-lipids and free FA it has been shown that FA absorption efficiency increases with unsaturation and that sole larvae spare DHA from catabolism. In addition, it was demonstrated that absorption efficiency varies according to molecular form, being highest for free FA, lowest for triacylglycerols and intermediate for phospholipids. Live preys commonly used in larviculture do not seem to have a balanced AA profile for sole larvae. Furthermore, the ideal dietary AA composition probably changes during development. Rotifers and Artemia metanauplii are apparently deficient in one or more of the following AA depending on the larval development stage: histidine, sulphur AA, lysine, aromatic AA, threonine and arginine. It has also been demonstrated that balancing the dietary AA profile with dipeptides inArtemia-fed larvae increases AA retention and reduces AA catabolism. When supplementing larval diets with limiting AA it should also be considered that sole larvae have different absorption, and retention efficiencies for individual AA, and that they have the capacity to spare indispensable AA. In addition, the absorption of free AA is faster and more efficient than that of complex proteins. Improvements in biochemical composition of inert microdiets for sole are likely to contribute to the reproducible weaning success of Senegalese sole.
- Weaning of Senegalese sole (Solea senegalensis) postlarvae to an inert diet with a co-feeding regime | Destete de postlarvas del lenguado senegalés (Solea senegalensis) a una dieta inerte utilizando un régimen de coalimentaciónPublication . Ribeiro, Laura; Engrola, S.; Dinis, Maria TeresaThe objective of this study was to evaluate the weaning success of Senegalese sole, Solea senegalensis, postlarvae when cofed a compound diet, by means of the analysis of growth parameters (relative growth rate [RGR] and condition factor [K]), survival, protein and lipid content. Total ammonia in the rearing water was also measured. The experiment lasted for 46 days (36 to 82 days posthatching). One group was fed only with enriched Artemia sp. metanauplii (Artemia treatment), whereas in another group, the Artemia sp. metanauplii were gradually replaced by the International Council for the Exploration of the Sea (ICES) diet over a period of 39 days (ICES treatment). Postlarvae were sampled on rearing days 0, 9, 23, 30, 39 and 46 for growth and biochemical analysis. Water was sampled on rearing day 30 during a 24-h cycle in both treatments. Postlarvae from the ICES treatment were weaned, though by the end of the experiment the Artemia treatment exhibited significantly higher values for growth, RGR, K and survival rates (P <0.05). No significant differences were observed concerning total lipid content. Protein content was significantly higher for the Artemia treatment after 46 days of rearing (P < 0.05). The total ammonia nitrogen concentration in the water increased after each meal and remained below a harmless level for postlarvae.
- Pigmentation abnormalities in juveniles sole Solea senegalensis Kaup, 1858 | Anomalías en la pigmentación de juveniles de lenguado Solea senegalensis Kaup, 1858Publication . Soares, Florbela; Engrola, S.; Dinis, Maria TeresaEl lenguado Solea senegalensis Kaup, 1858 es una especie de valor comercial elevado y está considerada de interés potencial para la acuicultura. En consecuencia, existe una creciente necesidad de desarrollar el cultivo larval de esta especie a escala industrial y producir juveniles para engorde en las piscifactorías. Se han realizado diversos trabajos con el objetivo de mejorar la metodología en la producción de S. senegalensis (Dinis, 1986, 1992; Dinis et al., 1999) y se señalan algunas limitaciones: entre ellas, las anomalías de pigmentación. Se describen aquí las principales anomalías en la pigmentación del lenguado a partir de puestas naturales de reproductores salvajes mantenidos en cautividad. El porcentaje total de alevines mal pigmentados fue del 11 %, lo que puede constituir un problema cuando se pretende la producción a gran escala, pues entraña un obstáculo para su comercialización, con el consiguiente descenso de la rentabilidad.
- Effect of pre-weaning feeding regime on weaning performance of Senegalese sole, Solea senegalensis (Kaup, 1858)Publication . Engrola, S.; Conceição, L. E. C.; Gavaia, Paulo J.; Cancela, Leonor; Dinis, Maria TeresaDespite much interest in the production of Senegalese sole (Solea senegalensis) in southern Europe, weaning of this species onto artificial diets is problematic and varying results are obtained. The aim of this study was to test two feeding frequencies during a 13-day pre-weaning period and assess their impact on the growth and survival of Senegalese sole. Postlarvae were fed Artemia metanauplii with a peristaltic pump every hour for 12 hours per day or twice daily (morning and late afternoon). Both groups were suddenly weaned onto a commercial diet for an additional 30 days. At the end of the experiment, the relative growth rate and final dry weight were significantly higher and the survival significantly lower in the 12-hour treatment than in the twice-daily treatment. The feeding frequency had no effect on condition factor. The incidence of deformities was about 80% in both treatments.