This study examined the growth, gut morphology and occurrence of endocrine cells in the gastrointestinal tract of silver catfish (Rhamdia quelen) fed diets supplemented with essential oil (EO) extracted from Aloysia triphylla (0control, 0.25, 0.5, 1.0 and 2.0 mL EO per kg of diet) for 60 days. The group fed 2.0 mL EO per kg of diet showed better results after 60 days in growth, body weight, weight gain and specific growth rate. Histological and immunohistochemical analyses in the intestine demonstrated that height of folds was significantly higher in the control group and 0.25 mL EO compared to those fed 0.5 mL EO per kg of diet. There was a significant increase in the number of folds in fish fed 1.0 and 2.0 mL EO per kg of diet compared to control group. The enterocyte height was significantly lower in those fed 1.0 mL of EO group compared with 0.25 mL of EO per kg of diet. The number of cells that reacted to cholecystokinin and neuropeptide Y did not differ between groups. The addition of 2.0 mL EO per kg of diet increases silver catfish growth, and consequently, its use is recommended as a feed additive.

This study was carried out to assess the effect of fasting and feeding on growth, intestinal morphology and density of cholecystokinin (CCK‐) and neuropeptide Y (NPY‐) immunoreactive cells in Rhamdia quelen. Fish were fed during 30 days with three commercial feeds containing different protein levels (T1 = 25%, T2 = 30% and T3 = 45%) while one group remained food deprived (T0). Our results show that the T3 group presented higher final mean weight and specific growth rate, while food‐deprived group showed a significant weight loss. Histological analyses showed that the epithelial area of the intestine was significantly affected by fasting. Also, immunohistochemical analyses showed changes in enteroendocrine cells density, according to nutritional status. Cholecystokinin cell density was higher in T2 and T3 groups, while no differences in NPY cell density were observed between fed groups. Neuropeptide Y and CCK cell densities decreased in fasted group. Nevertheless, this group presented a higher NPY:CCK cell ratio (5:1) compared to fed groups (1–1.5:1), suggesting NPY acts as a peripheral orexigenic factor. These results show that the structure and endocrine functions of R. quelen intestine respond with a downregulation mechanism to endure long‐term starvation.

No abstract

INTRODUÇÃOA produção de jundiá (Rhamdia quelen) em piscicultura é uma crescente atividade que deve ser baseada, entre outras coisas, na obtenção de larvas de boa qualidade. Embora tenha sido demonstrada a importância dos organismos vivos na alimentação das larvas de jundiá (LUCHINI & SALAS, 1985), nos últimos anos, os pesquisadores utilizaram outras estratégias alimentares, tais como a co-alimentação (organismos vivos + alimentos artificiais) (BEHR et al., 2000;CARNEIRO et al., 2003;HERNÁNDEZ et al., 2006) e os alimentos exclusivamente artificiais ULIANA et al., 2001;CARDOSO et al., 2004), os quais se mostraram mais vantajosos em relação ao alimento vivo, uma vez que sua produção é mais fácil e econômica (LAZO, 2000). Assim, diferentes fontes de proteína foram avaliadas para melhorar o desempenho em larvas de peixe. A utilização de fígado de aves cru na alimentação de larvas de jundiá demonstrou bons resultados no ganho de peso e na sobrevivência, em comparação com a farinha de hidrolisados de fígado ou peixe (CARDOSO et al., 2004).Além disso, foi avaliada a incorporação de probióticos nas rações artificiais, seja como fonte de proteína (PIAIA & RADÜNZ NETO, 1997)

SUMMARY:For successful fish larviculture thorough studies describing the development of fish in different morphological aspects are required, as they are crucial for larval survival and growth. The present study described in Prochilodus lineatus larvae the osteological development of the vertebral column and caudal skeleton 30 days after hatching (dah). Larvae were obtained by artificial induction of adults. The beginning of formation of the spine occurs between 10 to 12 dah (8.3 mm standard length, SL) simultaneously to the first neural and hemal processes and the pre-caudal vertebral bodies. The ossification of the vertebral column occurred in craniocaudal direction and was completed at 28 dah (22.6 mm SL). The development of the caudal skeleton elements started between 6 and 8 dah with the formation of the hypurals (H), the parahipural (PH) and the primary and secondary caudal rays. H 1 to H 3 were formed as cartilaginous primordia on the ventral side of the distal portion of the notochord, while the PH and H 4 to H 6 were formed subsequently. The first rays of the caudal fin were observed in correspondence with the formation of H 2 and H 3, while complete formation of the caudal fin was observed at 28 dah. The epurals, three in number, were evident as cartilaginous elements located both dorsal and distal in the notochord. Central ural complex (CUC) was formed by the fusion of three structures, the center preural 1 and urals 1 and 2. Development of the vertebral column and the caudal skeleton in P. lineatus larvae showed similar patterns to those described for other teleosts.