Salinidade da água durante a masculinização de tilápia-do-nilo em sistema de bioflocos

The objective of this work was to evaluate the effect of different water salinity levels on the growth performance, survival, and masculinization rate of Nile tilapia (Oreochromis niloticus) larvae in a biofloc technology (BFT) system. Seven salinity levels (0, 2, 4, 6, 8, 10, and 12 g L-1) were tested during four weeks in the masculinization period after the absorption of the yolk sac in a matured biofloc system. The water quality variables were within the recommended range for Nile tilapia farming. However, the nitrite peaks were higher at higher salinity levels and were associated with the lower survival of fish at salinity levels equal to or higher than 6 g L-1. There was no difference between treatments for average final body weight and masculinization rate. Final biomass and survival decreased, and the feed offered as a proportion of final biomass showed the worst results because of the increase in salinity. Therefore, since higher masculinization rates are not obtained at slight and moderate levels of saline water, salinity should be kept close to 0 g L-1 for the masculinization protocol of Nile tilapia in a BFT, for a better survival and higher biomass of the fish, as well as a lower waste of the offered feed.O objetivo deste trabalho foi avaliar o efeito de diferentes níveis de salinidade da água sobre o desempenho de crescimento, a sobrevivência e a taxa de masculinização de larvas de tilápia-do-nilo (Oreochromis niloticus) em sistema de tecnologia de bioflocos (BFT). Sete níveis de salinidade (0, 2, 4, 6, 8, 10 e 12 g L-1) foram testados durante quatro semanas no período de masculinização após a absorção do saco vitelino, em sistema de bioflocos maturados. As variáveis de qualidade da água estiveram dentro dos intervalos recomendados para a produção de tilápia-do-nilo. Entretanto, os picos de nitrito foram mais altos nos tratamentos com maiores níveis de salinidade e foram associados à menor sobrevivência dos peixes em salinidade igual ou superior a 6 g L-1. Não houve diferença entre os tratamentos quanto ao peso médio final e à taxa de masculinização. A biomassa final e a sobrevivência diminuíram, e o alimento oferecido como proporção da biomassa final apresentou os piores resultados em razão do aumento da salinidade. Portanto, uma vez que não são obtidas taxas de masculinização maiores em água leve ou moderadamente salinizada, a salinidade deve ser mantida próxima de 0 g L-1 para o protocolo de masculinização de larvas de tilápia-do-nilo em BFT, para melhor sobrevivência e maior biomassa dos peixes, assim como menor desperdício do alimento oferecido

Successful xenogeneic germ cell transplantation from Jundia catfish (Rhamdia quelen) into adult Nile tilapia (Oreochromis niloticus) testes

Fish germ cell transplantation presents several important potential applications for aquaculture, including the preservation of germplasm from endangered fish species with high genetic and commercial values. Using this technique in studies developed in our laboratory with adult male Nile tilapias (Oreochromis niloticus), all the necessary procedures were successfully established, allowing the production of functional sperm and healthy progeny approximately 2 months after allogeneic transplantation. In the present study, we evaluated the viability of the adult Nile tilapia testis to generate sperm after xenogeneic transplant of germ cells from sexually mature Jundia catfish (Rhamdia quelen) that belong to a different taxonomic order. Therefore, in order to investigate at different time-periods post-transplantation, the presence and development of donor PKH26 labeled catfish germ cells were followed in the tilapia seminiferous tubules. From 7 to 20 days post-transplantation, only PKH26 labeled spermatogonia were observed, whereas spermatocytes at different stages of development were found at 70 days. Germ cell transplantation success and progression of spermatogenesis were indicated by the presence of labeled PKH26 spermatids and sperm on days 90 and 120 post-transplantation, respectively. Confirming the presence of the catfish genetic material in the tilapia testis, all recipient tilapias evaluated (n = 8) showed the genetic markers evaluated. Therefore, we demonstrated for the first time that the adult Nile tilapia testis offers the functional conditions for development of spermatogenesis with sperm production from a fish species belonging to a different order, which provides an important new venue for aquaculture advancement. © 2016 Elsevier Inc

Digestibilidade de ingredientes em dietas para juvenis de pacamã (Lophiosilurus alexandri)

The objective of this work was to determine the apparent digestibility coefficient (ADC) of six ingredients, in practical and purified reference diets, and to assess the influence of these reference diets on the digestibility of the ingredients in pacman catfish juveniles. The following ingredients were evaluated: fish meal, meat and bone meal, soybean meal, roasted whole soybean, wheat meal, and corn protenose. There was interaction between the reference diet and the studied ingredients. The purified diet provided higher ADC for crude protein and gross energy. Pacman catfish showed high ADC for protein ingredients of vegetable origin for the two reference diets.O objetivo deste trabalho foi determinar o coeficiente de digestibilidade aparente (CDA) de seis ingredientes, em dietas‑referência prática e purificada, e determinar a influência das dietas‑referência sobre a digestibilidade dos ingredientes em juvenis de pacamã. Avaliaram-se os seguintes ingredientes: farinha de peixe, farinha de carne e ossos, farelo de soja, soja integral tostada, farelo de trigo e protenose de milho. Houve interação entre a dieta‑referência e os ingredientes estudados. A dieta purificada proporcionou maior CDA quanto à proteína bruta e energia bruta. O pacamã apresentou CDAs elevados quanto aos ingredientes proteicos de origem vegetal, nas duas dietas‑referência.

Stocking density in the larviculture of Nile tilapia in saline water

The objective of this study was to assess the possibility of increasing the stocking density in the larviculture of Nile tilapia, Oreochromis niloticus, in saline water. Six-day post-hatched larvae (average weight of 0.09±0.002 g), at the start of the exogenous feeding, were stocked in twelve 8 L tanks at densities of 1, 10, 20 and 30 larvae/L. The larvae were fed a diet consisting of 40% crude protein five times per day. During larviculture, water was kept at a salinity of 2 g of common salt/L. At the end of the 28-day experiment, the survival rate, length, weight, temperature, water salinity and conductivity were not affected by the different treatments. The dissolved oxygen and pH, however, decreased as density increased, whereas total ammonia concentration, turbidity and biomass showed a direct relationship with the increase of stocking density. Consequently, the present study shows for the first time that the larviculture of Nile tilapia is possible with up to 30 larvae/L in water with 2 g of salt/L