RESUMO O presente estudo foi realizado para determinar a exigência de lisina pela tilápia do Nilo (Oreochromis niloticus).Setenta e dois peixes revertidos sexualmente e com peso vivo médio inicial de 117,9 ± 0,67g

Este estudo foi realizado para determinar a exigência de metionina + cistina para alevinos de tilápia do Nilo (2,61 ± 0,14g). Foi utilizado o modelo em blocos ao acaso, com seis tratamentos, três repetições e cinco peixes por unidade experimental. Foi utilizada ração basal contendo 28% de proteína bruta e 3173kcal ED kg-1 de ração, suplementada com DL-metionina, resultando em rações com 0,87; 0,95; 1,03; 1,11; 1,19 e 1,27% de metionina + cistina. As rações foram fornecidas à vontade durante 41 dias. Não foram observados efeitos (P>0,05) dos níveis de metionina + cistina sobre a taxa de sobrevivência e índice hepato-somático. Foi observado efeito quadrático (P<0,05) sobre o ganho de peso, que aumentou até o nível de 1,22% de metionina + cistina na ração. A conversão alimentar e a taxa de eficiência protéica aumentaram (P<0,05) até o nível de 1.00% de metionina + cistina. Foi observado efeito quadrático (P<0,05) sobre o rendimento de carcaça que aumentou até o nível de 1,13% de metionina + cistina. O nível de 1,00% de metionina + cistina, correspondente a 3,54% da proteína bruta, contendo 0,54% de metionina na ração, mostrou melhor resultado no desempenho.

RESUMO.Este trabalho foi realizado para avaliar a influência de níveis de fitase sobre o desempenho da tilápia do Nilo (Oreochromis niloticus) no período de reversão de sexo. Foram utilizadas 1000 larvas de tilápia do Nilo com peso inicial 0,02 ± 0,002g, alimentadas com rações contendo 0; 500; 1000; 2000 e 4000 unidades de fitase (UF)/kg, durante 31 dias. A ração referência continha 3143 kcal de energia digestível/kg, 30% de proteína bruta e 0,85 e 0,35% de fósforo (P) total e disponível, respectivamente. Não foram observados efeitos (P>0,05) dos valores de inclusão de fitase sobre o ganho de peso e taxa de sobrevivência. O aumento nos níveis de fitase nas rações elevou linearmente (P<0,05) a retenção de cálcio na carcaça. Foi observado efeito quadrático (P<0,05) das rações suplementadas com fitase sobre a retenção de fósforo na carcaça, estimando-se o valor de 1990 UF/kg para maior valor desta variável. Os resultados deste trabalho indicam que o nível de 1990 unidades fitase/kg de ração proporciona máxima retenção de fósforo na carcaça da tilápia do Nilo durante o período de reversão de sexo.Palavras-chave: desempenho, fitase, Oreochromis niloticus, retenção de P, reversão sexual. ABSTRACT. Phytase as feeding for Nile tilapia (Oreochromis niloticus), during sex reversion period. This work was carried out to examine the influence of dietary levels of phytase on Nile tilapia (Oreochromis niloticus) performance during the sex reversion period. Were used 1,000 fries of Nile tilápia with initial weight 0.02 ± 0.002g, fed with diets containing 0; 500; 1000; 2000 and 4000 phytase units (PU)/kg of diet 31 days. The reference diet provided 3,143 kcal of digestible energy/kg, 30% of crude protein and 0,85 and 0,35% of total and disponible phosphorus (P), respectively. No effects (P>0.05) were observed of phytase inclusion on weight gain and survival rate. Dietary phytase levels increase linearly (P<0.05) the calcium retention in the carcass. There was observed quadratic effect (P<0.05) of dietary phytase supplementation on P retention in the carcass, estimated the values of 1,990 PU/kg for the highest value for this variable. The results of this work indicate that a dietary level of 1,990 of PU provide maximal P retention in the carcass of Nile tilapia, during sex reversal period.

Cryopreservation of germplasm provides a promising method to preserve fish genetic material, which is of great importance in preservation of species diversity, aquaculture, and management of fish models used in biomedical research. In the present study, cryopreservation of Rhinelepis aspera embryos, a Brazilian endangered species, was studied for the first time using a short-term cooling protocol. Embryos at blastoporous closing stage were selected, placed in 6-ml glass vials and stored at -8 °C for 6 h in 10 different cryoprotectant solutions: S1 (17.1% sucrose + 9% methanol); S2 (17.1% sucrose + 9% DMSO); S3 (8.5% sucrose + 8.5% glucose + 9% methanol); S4 (8.5% sucrose + 8.5% glucose + 9% DMSO); S5 (17.1% sucrose + 9% ethylene glycol); S6 (8.5% sucrose + 8.5% glucose + 9% ethylene glycol); S7 (17.1% sucrose + 4.5% methanol + 4.5% DMSO); S8 (17.1% sucrose + 4.5% methanol + 4.5% ethylene glycol); S9 (17.1% sucrose + 4.5% DMSO + 4.5% ethylene glycol); and S10 (100% water). Embryo viability was assessed by hatching rate, counting live larvae and number of failed eggs under a stereomicroscope. The results showed that only the cryoprotectant solutions that contained methanol associated to sucrose (S1, S7 and S8) provided partial protection of Rhinelepis aspera embryos from cold damage (over 50% hatching rate in S1), while the use of DMSO and ethylene glycol, isolated or in combination, resulted in no hatching rate. Further studies are needed in order to extend the storage time and to improve the hatching rate for the species.

Este experimento foi realizado para determinar as exigências nutricionais de metionina + cistina total e digestível para alevinos revertidos de tilápia do Nilo (Perciformes, Cichlidae). Durante 40 dias, alevinos com 1,31 ± 0,06 g cada, foram alimentados com rações com 0,89; 0,94; 0,99; 1,09; 1,19 e 1,29% de metionina + cistina total, correspondente a 0,83; 0,88; 0,93; 1,03; 1,13 e 1,23% de metionina + cistina digestível. As rações foram suplementadas com níveis crescentes de DL-metionina, resultando em rações com taxas 50,61; 0,54; 56,7; 62,80; 68,90 e 75% de metionina + cistina/lisina (conceito de proteína ideal), baseado em valores de aminoácidos digestíveis. Os níveis crescentes de metionina + cistina reduziram linearmente a taxa de sobrevivência. As rações com níveis de 1,10% e 1,00% de metionina + cistina total e digestível, respectivamente, apresentaram os melhores resultados sobre o desempenho de alevinos de tilápias, correspondente a rações com 60,11 e 60,98% de metionina + cistina total e digestível/lisina total e digestível, respectivamente. Palavras-chave: alevinos, metionina + cistina, Oreochromis niloticus, proteína ideal, tilápia do Nilo. ABSTRACT. Nutritional requirements of total and digestible methionine + cystine for reversed fingerlings of the Nile tilapia Oreochromins niloticus (L.) based on the ideal protein concept. The nutritional requirements of total and digestible methionine for reversed fingerlings of the Nile tilapia (Perciformes, Cichlidae) were determined. During a 40-day period fingerlings, weighing 1.31 ± 0.06g each, were fed on diets with 0.89; 0.94; 0.99; 1,09; 1.19 and 1.29% of total methionine + cystine, corresponding to 0.83; 0.88; 0.93; 1.03; 1.13 and 1.23% of digestible methionine + cystine. Since diets were supplemented with increasing levels of DL-methionine, diets reached 50.61; 0.54; 56.7; 62.80; 68.90 e 75% of methionine + cystine/lysine ratio (ideal protein concept), based on digestible amino acids values. Increasing methionine + cystine levels linearly diminished survival rate. Diets with 1.10% and 1.00% levels of total and digestible sulfur amino acid respectively had the best performance results for Nile tilapia fingerlings. This corresponds to 60.11 and 60.98% of total and digestible methionine + cystine/total and digestible lysine respectively.

Although the sperm cryopreservation of freshwater and marine teleosts has been feasible for years, the cryopreservation of some fish embryos still remains elusive. Thus, the objective of this experiment was to analyze the embryo morphology after freezing and thawing 40 embryos of Piaractus mesopotamicus immersed into methanol and ethylene glycol, both at 7, 10 and 13% plus 0.1 M sucrose for 10 min. Soon after thawing, three embryos were treated with historesin, stained with hematoxylin-eosin and analyzed under an optical microscope. From every treatment, one palette containing embryos was thawed and incubated, but none of the eggs hatched. Samples containing two embryos were immersed into 10% methanol or 10% ethylene glycol both in association with sucrose, and embryos immersed into only water or sucrose solution were frozen, processed and analyzed using scanning electron microscopy (SEM). In both cases, the control group was immersed into only water. Although the embryos had the chorion, vitello, yolk syncytial layer and blastoderm, all of them were found altered under the optical microscope and by SEM. The chorion was irregular and injured; there was no individuality in the yolk granules; the yolk syncytial layer had an irregular shape, thickness and size; the blastoderm showed injuries in the nucleus shape and sometimes was absent; the blastoderm was located in atypical areas and absent in some embryos. In conclusion, no treatment was effective in preserving the embryos, and none of the embryos avoided injury from intracellular ice formation. These morphological injuries during the freezing process made the P. mesopotamicus embryos unfeasible for hatching.

ABSTRACT

This study was carried out to morphologically characterize and classify the stages of gonad development in different Nile tilapia strains (Oreochromis niloticus). Eighty-four and ninety-two ovaries from Bouaké and Chitralada strains, respectively, were evaluated at different ovarian developmental phases: initial (104 days of culture), intermediate (152 days of culture), and the final (279 days of culture). The ovaries were microscopically evaluated and submitted to histological processing and hematoxylin-eosin staining to determine their characteristics and be classified. No morphological differences in ovaries between strains were observed during the initial phase (stage A -immature). During the intermediate growing phase, higher gonad development was observed for Chitralada strain (stage B -maturation) in comparison with Bouaké strain (stage A -immature). During the final growing phase, no differences between strains were observed for morphological characteristics (stage C -mature). Despite the similarities in reproductive behavior of the Bouaké and Chitralada females at the end of the final growing phase (gain weight phase), differences for macroscopic and microscopic aspects and oocytes during the initial and intermediate growing phases of the strains were observed.Keywords: Oreochromis niloticus, morphology, ovarian development, strain RESUMO Este trabalho teve como objetivo caracterizar morfologicamente e classificar os estádios de desenvolvimento gonadal de tilápias do Nilo (Oreochromis niloticus) de linhagens distintas. Foram avaliados 84 ovários da linhagem Bouaké e 92 da linhagem Chitralada, em diferentes fases de desenvolvimento: inicial (imatura -104 dias de cultivo), intermediária (crescimento -152 dias de cultivo) e final (ganho de peso -279 dias de cultivo). Os ovários foram analisados macroscopicamente e submetidos a procedimento histológico, corados com hematoxilina-eosina, para determinação das características microscópicas e subsequente classificação. Não foram observadas diferenças morfológicas nos ovários entre as linhagens na fase inicial (estádio A -imaturo). Na fase intermediária, os ovários revelaram diferenças morfológicas, evidenciando maior desenvolvimento gonadal para a linhagem Chitralada, (estádio B -maturação) em relação à Bouaké (estádio A). Na fase final (ganho de peso) os ovários não apresentaram diferenças morfológicas entre as linhagens (estádio C -maduro