Artigos

Abstract

The need for a sustainable aquaculture is increasing the use of plant ingredients in replacement to fishmeal and fish oil in diets for tambaqui Colossoma macropomum, which is leading to not detectable levels of docosahexaenoic acid (DHA) in its flesh. We evaluated the effect of a finishing plant diet supplemented with 5% of microalgae meal from Schizochytrium sp. (MD) on tambaqui growth, on proximal composition and fatty acid content of its flesh, comparing it to a non‐supplemented diet. One hundred and sixty‐two fish (489.67 g) were distributed into six tanks (2,000 L) and fed the experimental diets for a 90‐day period. Three fish per tank were euthanized for analyses every 15 days. The MD did not affect the growth and proximal composition of fish flesh. The MD increased the DHA content (from 14.81 to 38.60 mg/g of lipids) and the n‐3:n‐6 ratio (from 0.16 to 0.51) in the flesh of fish, beginning on the 15th day and reaching the highest DHA content on the 71st day (39.81 mg/g of lipids). We recommend C. macropomum to be fed with a finishing diet supplemented with microalgae meal for 71 days before slaughter to improve the DHA content and n‐3:n‐6 ratio in the flesh.

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Abstract

The practice of indoor larviculture can be an alternative to enhance the rearing of arapaima larvae, improving their survival and the supply of arapaima juveniles for the grow-out stage. We aimed to evaluate different live microcrustaceans as feed for arapaima larvae to verify groups that can be safely used in laboratory trials, as well as in commercial larviculture. Arapaima larvae (39.45 ± 7.04 mg and 2.09 ± 0.13 cm) were housed in 12-L circular tanks (n = 4 tanks; 30 larvae per tank) in a static water system. The tanks were cleaned twice a day, when 50% of the water was changed. Fish were fed three types of live feed 9 times/day: brine shrimp Artemia sp. nauplii (AR), Cladocera-rich zooplankton (CZ), and Ostracoda-rich zooplankton (OZ) for 15 days. Fish fed CZ and AR showed a similar fast growth rate with low mortality rates. The OZ fed Arapaima larvae presented intact Ostracoda in their rectums. This findins, demonstrates their poor digestibility, which resulted in poor growth and low survival. Ostracoda-rich zooplankton must be avoided in arapaima larviculture until 8 days after they begin swimming to the water surface or 17 days after hatching.

51679976_558810461302740_266343208637903

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Abstract

Early‐life survival of Arapaima gigas is one of the main challenges of its farming. In this study, we described the morphological and histochemical development of the gastrointestinal tract of arapaima larvae. Larvae were collected from a pond when they started to swim to the water surface (initial day) and were housed in indoor tanks. Daily samplings (n = 10) were performed from 0 to the 11th day after the collection (DAC) and then on the 14th, 17th, and 20th DAC. On the initial day, arapaima larvae (0.05 ± 0.01 g; 2.21 ± 0.06 cm) had opened mouth and anus and no yolk sac. In addition, larvae presented well‐developed digestive organs. Gastric glands were fully formed, with positive reactions to alcian blue (AB) pH 1.0 as well as to periodic acid‐Schiff (PAS) in the simple columnar epithelium. There were folds throughout the intestine and brush border, with an AB pH of 2.5 + PAS positive mucins. From 1 to 11 DAC, larvae presented increasing concentrations of gastric glands and thickness of the stomach muscular layer. From 14 to 20 DAC, the intestine presented high‐fold complexity. We suggest that arapaima larvae may be fed exogenous inert diets at a size of around 2 cm.

36919052_422427911607663_254311810811402

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Abstract

The aim of this study was to evaluate the survival and growth of Arapaima gigas larvae reared in slightly salinized water. Pirarucu larvae (183.1 ± 41.2 mg and 3.4 ± 0.3 cm) were stocked in PVC tanks (20 L; n = 4; 40 larvae per tank) in a static system. A. gigas larvae were reared in increasing levels of salinized water (0, 1, 2, 3 and 4‰) for a period of 15 days. Fish were fed six times a day with Artemia nauplii (2,900 nauplii per larvae per meal in the beginning). The salinized water increased by at least four times the Artemianauplii lifespan, which prolonged the time of live food supply to Arapaima larvae. Pirarucu larvae kept in freshwater presented the lowest values in weight gain, final weight and survival. Larvae reared in water with 4‰ of salinized water showed the highest final weight. Slightly salinized water enhances the growth and survival of A. gigas larvae and it can be a simple practice with low cost that can be applied in the routine of pirarucu larviculture.routine of pirarucu larviculture.

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Abstract

The fish heart ventricle has varied morphology and may have a specific morpho‐functional design in species adapted to extreme environmental conditions. In general, the Amazonian ichthyofauna undergoes constant variations in water temperature, pH and oxygen saturation, which makes these species useful for investigations of cardiac morphology. Arapaima gigas, a member of the ancient teleost group Osteoglossomorpha, is one of the largest freshwater fish in the world. This species has a specific heart metabolism that uses fat as the main fuel when O2 supplies are abundant but also can change to glycogen fermentation when O2 content is limiting. However, no information is available regarding its heart morphology. Here, we describe the heart of A. gigas, with emphasis on the ventricular anatomy and myoarchitecture. Specimens of A. gigasweighing between 0.3 and 4040 g were grouped into three developmental stages. The hearts were collected and the anatomy analyzed with a stereomicroscope, ultrastructure with a scanning electron microscope, and histology using toluidine blue, Masson's trichrome and Sirius red stains. The ventricle undergoes morphological changes throughout its development, from the initial saccular shape with a fully trabeculated myocardium and coronary vessel restricted to the subepicardium (Type I) (group 1) to a pyramidal shape with mixed myocardium and coronary vessels that penetrate only to the level of the compact layer (Type II) (groups 2 and 3). The trabeculated myocardium has a distinct net‐like organization in all the specimens, differing from that described for other teleosts. This arrangement delimits lacunae with a similar shape and distribution, which seems to allow a more uniform blood distribution through this myocardial layer.presented increasing concentrations of gastric glands and thickness of the stomach muscular layer. From 14 to 20 DAC, the intestine presented high‐fold complexity. We suggest that arapaima larvae may be fed exogenous inert diets at a size of around 2 cm.

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