Morphology of the digestive system in carnivorous freshwater dourado Salminus brasiliensis.

The digestive system of teleost shows remarkable functional and morphological diversity. In this study, the digestive tract and accessory organs of dourado Salminus brasiliensis are characterized using anatomical, histological, histochemical and immunohistochemical analyses. The existence of taste buds bordered by microridges in the oesophagus of dourado was recorded for the first time, thus showing that the species drives food intake by either swallowing or rejecting the food item. The Y-shaped stomach of dourado consisted of cardiac, cecal and pyloric regions with tubular gastric glands registered solely in the cardiac and cecal segments. The intestine is a short N-shaped tube with two loops, an intestinal coefficient of 0.73. The structure of pyloric caeca is similar to that of the intestine wall, comprising tunica mucosa, tela submucosa, tunica muscularis and tunica serosa layers. Histochemical analyses revealed an increased incidence of goblet cells from the midgut to the hindgut segment. A well-developed enteric plexus of scattered nerve cell and fibres are found along the digestive tract, and the calcitonin gene-related peptide (CGRP) immunoreactive neurons and fibres were identified in the myenteric plexus from the oesophagus to the hindgut. The exocrine pancreas appears diffuse in the mesentery around the stomach, intestine and also reaches the liver, and the endocrine pancreas is organized as a few islets of Langerhans. The liver comprises three distinct, asymmetric lobes, and the portal triad arrangement was registered in this tissue.

Metabolic responses to dietary carbohydrate/lipids ratios in neotropical hybrid catfish (♂Pseudoplatystoma corruscans×♀Pseudoplatystoma fasciatum).

The purpose of this study was to assess the effect of different carbohydrate and lipid (CHO/L) ratios on the performance and energy metabolism of hybrid catfish (♂Pseudoplatystoma corruscans × â™€ Pseudoplatystoma fasciatum). One hundred and sixty-eight fish (104.9±16.5 g BW) were distributed into 24 100-L tanks. The experiment was performed using a randomised block design with four CHO/L ratios (0.45, 1.00, 1.66 and 2.85) and six replications. Growth performance, protein content, glucose and triglycerides in plasma, muscle and liver, and the hepatic activity of the malic and glucose-6-phosphate dehydrogenase (G6PD) enzymes were measured after 60 feeding days. No significant differences were observed in growth performance, protein and triglycerides of plasma and muscle, hepatic protein or malic enzyme activity. CHO/L: 2.85 provided the highest plasma and liver glucose, while CHO/L: 0.45 showed high liver triglycerides. A linear effect was found for the hepatic activity of G6PD and dietary starch levels (R2=0.93). The hepatic activity of G6PD was greater in CHO/L=2.85 than for CHO/L: 0.45. In conclusion, the limit of dietary starch inclusion and lipids were 15% and 9.00%, respectively (CHO/L: 1.66), and this level did not affect the energy metabolism of the juvenile hybrid catfish.

Daily rhythms of the expression of genes from the somatotropic axis: The influence on tilapia (Oreochromis niloticus) of feeding and growth hormone administration at different times.

The aim of this research was to investigate the presence of daily rhythms in the somatotropic axis of tilapia fed at two times (mid-light, ML or mid-dark, MD) and the influence of the time of day of growth hormone (GH) administration on the response of this axis. Two different GH injection times were tested: ZT 3 (3h after lights on) and ZT 15 (3h after lights off). In both experiments, the mRNA expression levels of hypothalamic pituitary adenylate cyclase-activating polypeptide (pacap), pituitary growth hormone (gh), liver insulin-like growth factors (igf1 and igf2a), and liver and muscle growth hormone receptors (ghr1 and ghr2) and IGF receptors (igf1ra and igf2r) were evaluated by means of qPCR. Daily rhythms were observed in the liver for ghr1, ghr2 and igf2r but only in fish fed at ML, with the acrophases located in the light phase (ZT 3:30, 3:31 and 7:38 h, respectively). In the muscle, ghr1 displayed a significant rhythm in both groups and ghr2 in ML fed fish (acrophases at ZT 5:29, 7:14 and 9:23h). The time of both GH administration and feeding influenced the response to GH injection: ML fed fish injected with GH at ZT 15 h showed a significant increase in liver igf1, igf2a and ghr2; and muscle ghr2 expression. This is the first report that describes the existence of daily rhythms in the somatotropic axis of tilapia and its time-dependent responses of GH administration. Our results should be considered when investigating the elements of the somatotropic axis in tilapia and GH administration.

Effect of fixed feeding time on growth, body composition, and hepatic histology of hybrid catfish (Pseudoplatystoma reticulatum x Leiarius marmoratus) fed with carbohydrates and lipids ratios / Efecto de la alimentación a tiempo fijo sobre el crecimiento, composición corporal e histología hepática del bagre híbrido (Pseudoplatystoma reticulatum x Leiarius marmoratus) alimentado con proporciones de carbohidratos y lípidos / Efeito do tempo de alimentação fixa no crescimento, composição corporal e histologia hepática do bagre híbrido (Pseudoplatystoma reticulatum x Leiarius marmoratus) alimentados com relações de carboidrato e lipídios

Background: feed and light are the most important factors affecting the biological rhythms of fish. This work studies fish adaptation to those factors. Objetive: to determine the influence of feeding time and dietary starch and lipid levels on growth, body composition, and liver histology of hybridized Brazilian catfish. Methods: two isoenergetic diets were formulated to contain two levels of crude starch (CHO, %) and lipids (L, %): 5/11 CHO/L and 25/2.2 CHO/L. Sixty animals (260 ± 10 g) were randomly distributed into twelve tanks (100 L). Using self-feeders, two fish groups were fed a diet containing either 5% or 25% starch during the light period (ML), while other two groups were fed the same diets during the dark period (MD). The following parameters were measured: final weight, weight gain, specific growth rate, food intake, hepatosomatic index, and viscerasomatic index. The experiment was carried out in triplicate for 60 days. Results: growth parameters such as specific growth rate (SGR), final weight, and weight gain showed statistical differences between groups, with the best results for the group fed the 25% starch diet during ML. Significant differences between groups on body lipid content, energy, and dry weight were also recorded for those feed 25% starch in the MD. A significant effect was also observed on liver lipid and glycogen content, with values generally higher for ML with 5% starch. Fish fed 25% starch showed significantly lowest lipid and glycogen content during ML. Surprisingly, the opposite occurred regarding liver composition for fish fed in MD. Conclusions: we suggest diurnal feeding should be practiced for optimal performance of juvenile fish, however dark or light phases could be used, taking into consideration its relationship with carbohydrate levels.

Antecedentes: la alimentación y la luz son los factores más importantes que afectan los ritmos biológicos en peces. En este artículo se presenta un poco de conocimiento acerca de la plasticidad de los peces para la utilización del alimento. Objetivo: este estudio se realizó para determinar la influencia del horario de alimentación y los niveles de almidón y lípidos de la dieta en el crecimiento, la composición corporal y la histología hepática en el bagre híbrido. Métodos: fueron formuladas dos dietas isoenergéticas para contener dos niveles de almidón (CHO, %) y lípidos (L, %): 5/11 CHO/L y 25/2.2 CHO/L. Sesenta animales (260 ± 10 g) fueron distribuidos aleatoriamente en 12 tanques (100 L). Un grupo de peces fue alimentado con 5% de almidón en el periodo diurno (ML), y otro grupo fue alimentado en el periodo nocturno (MD). Se realizaron los mismos procedimientos para el grupo alimentado con 25% de almidón. Los siguientes parámetros fueron medidos: peso final, ganancia de peso, tasa de crecimiento especifico, ingestión alimentaria, índice hepatosomático y índice vicerosomático. El experimento se realizó por triplicado durante 60 días. Resultados: los parámetros de crecimiento como la tasa de crecimiento específico (SGR), peso final y ganancia de peso mostraron diferencias estadísticas entre los grupos, con mejores resultados en los grupos alimentados con 25% de almidón en ML. Se observaron diferencias significativas entre los grupos para el contenido de lípidos en el cuerpo, energía y materia seca, para los animales alimentados con 25% de almidón en MD. Hubo un efecto significativo sobre los lípidos hepático y glucógeno, con los valores generalmente más altos en ML para los peces alimentados con 5% de almidón. Sin embargo, los peces alimentados con 25% de almidón presentaron significativamente menor contenido de lípidos y glucógeno en la condición de ML. Sin embargo, ocurrió lo contrario con los peces alimentados en MD, para la composición del hígado. Conclusiones: la alimentación diurna se sugirió para un mejor rendimiento de los juveniles, sin embargo, la fase nocturna o de luz se podrían utilizar, teniendo en cuenta su relación con los niveles de carbohidratos.

Antecedentes: alimentos e luz são os fatores mais importantes que arrastam os ritmos biológicos em peixes. Neste trabalho, trazemos um pouco do conhecimento sobre a plasticidade dos peixes para a utilização dos alimentos. Objetivo: este estudo foi realizado para determinar a influencia do horário de alimentação e níveis de amido e lipídio dietético no crescimento, composição corporal e histologia hepática em um bagre hibrido. Métodos: duas dietas isoenergéticas foram formuladas para conter dois níveis de amido (CHO, %) e lipídeo (L, %): 5/11 CHO/L e 25/2.2 CHO/L. Sessenta animais (260 ± 10 g) foram distribuídos aleatoriamente em 12 tanques (100 L). Um grupo de peixes foi alimentado com 5% de amido no período diurno (ML), e outro grupo foi alimentado no período noturno (MD). Os mesmos procedimentos foram realizados para o grupo que de alimentava com 25% de amido. Os seguintes parâmetros foram medidos: peso final, ganho de peso, taxa de crescimento especifico, consumo, índice hepatossomático y índice vicerossomático. O experimento foi conduzido em triplicado por 60 dias. Resultados: os parâmetros de crescimento como SGR, peso final e ganho de peso mostraram diferença estatística entre os grupos, com melhores resultados nos grupos alimentados com 25% de amido em ML. Diferença significativa entre grupos para conteúdo de lipídio na carcaça, energia e material seca foram observados para os animais alimentados com 25% de amido em MD. Foi observado efeito significativo no lipídio hepático e glicogênio com valores em geral mais altos em ML para os peixes alimentados com 5% de amido. Entretanto, os peixes alimentados com 25% de amido mostraram significativamente baixo conteúdo de lipídio e glicogênio sobre a condição de MD. Surpreendentemente, o oposto correu com os peixes alimentados em MD, para a composição do fígado. Conclusões: a alimentação diurna foi sugerida para um melhor desempenho dos juvenis, no entanto, a fase noturna ou de luz poderiam ser usados , levando em consideração sua relação com os níveis de carboidratos.

Efecto de tres tipos de presas vivas en la larvicultura de bagre blanco (Sorubim cuspicaudus) / Efect of three types of live preys on larviculture of the trans-andean shovelnose catfish (Sorubim cuspicaudus)

Objetivo. Evaluar el efecto de diferentes presas vivas en la larvicultura de bagre blanco (Sorubim cuspicaudus). Materiales y métodos. Al inicio de la alimentación exógena de Sorubim cuspicaudus, se ofreció zooplancton producido en mesocosmos (T1), zooplancton silvestre (T2) y nauplios de Artemia (T3), en concentración de 10.000 zoop/L, dos veces al día, durante seis días. Se utilizaron 18 acuarios de cinco litros de volumen útil, con densidad de 25 Larvas/L, seis réplicas por tratamiento en un diseño al azar. Se estimaron la ganancia en peso (Gp) y longitud (Gl), tasa de crecimiento específico (G), sobrevivencia (S), resistencia al estrés (Re), mortalidad acumulada (Ma) y mortalidad por canibalismo (Mc). Resultados. Las larvas alimentadas con mesocosmos presentaron la mayor sobrevivencia (81.3±15.9%); aunque el mejor crecimiento lo presentaron las larvas alimentadas con zooplancton silvestre (T2) las cuales presentaron la mayor mortalidad (42.0±10.7%) y la menor resistencia al estrés (30.0±33.0%). El canibalismo se observó en todos los tratamientos, oscilando entre 4.0 (T2) y 14.3% (T1) sin diferencias significativas entre estos valores (p>0.05). Conclusiones. El uso de zooplancton producido bajo condiciones controladas permitió una alta sobrevivencia, adecuado desempeño y resistencia de las larvas, perfilándose como alternativa viable en la primera alimentación de bagre blanco.

Objective. Assess the effect of different live prey in the larviculture of Trans-andean shovelnose catfish (Sorubim cuspicaudus). Materials and methods. At the beginning of exogenous feeding, zooplankton produced in mesocosm (T1), wild zooplankton (T2) and brine shrimp (T3), in concentrations of 10.000 zoop/L, were fed twice daily, for six days. 18 five-liter useful volume aquariums were used, with density of 25 Larvas/L, and six replicas per treatment in a random design. The increase in weight (Gp) length (Gl), the specific growth rate (G), survival (S), stress resistance (Re), accumulated mortality (Ma) and mortality due to cannibalism (Mc) were measured. Results. Larvae fed with mesocosm presented the highest survival rate (81.3±15.9%), although larvae fed wild zooplankton (T2) had the highest growth (Gp, Gl, G), and recorded the highest accumulated mortality (42.0±10.7%) and the lowest resistance to stress (30.0±33.0%). Cannibalism was observed in all treatments, ranging from 4.0 (T2) to 14.3% (T1) no significant difference between these values (p>0.05) was observed. Conclusions. The use of zooplankton produced under controlled conditions allows high survival, adequate performance and resistance of the larvae, emerging as viable alternative for the first feeding of white catfish.