Maria Goreti de Almeida Oliveira

Desempenho e atividade de amilase em tilápias-do-nilo submetidas a diferentes temperaturas

Abstract€–€ The€objective of this work was to evaluate the performance and amylase activity in chime of Niletilapia male, Thai line, submitted to four different temperatures. The experimental design was completely randomizedwith four treatments (20, 24, 28 and 32 o C), six replicates and ten fishes per experimental unit. The diet was thesame for all treatments. At 55€days of experiment, apparent feed intake, weight gain, apparent feed conversion,amylase activity and specific amylase activity were evaluated. The apparent feed intake and weight gain increasedlinearly with temperature increase. For apparent feed conversion, quadratic effect was observed as a function oftemperature, showing a conversion improvement of 1.79 to 1.00 with the increase of the temperature until 29,15 o C.Linear effect in amylase activity and specific amylase activity was observed as a result of temperature, comprisinghigh amylase activity and low specific amylase activity at 32 o C. Water temperature influences the performanceand amylase activity in Nile tilapia.Index terms:

Propriedades físico-químicas de polifenoloxidase de feijão (Phaseolus vulgaris L.)

The polyphenoloxidase activity of nine bean (Phaseolus vulgaris L.) cultivars (Arua, Apore, A774, Carioca, Diamante Negro, Ouro Branco, Perola, RAO 33 e Ruda) were studied. The crude enzyme extract of the nine cultivars was found to have optimum pH in 7.2 using catechol as substrate. No PPO activity in beans (Phaseolus vulgaris L.) was observed using D,L DOPA and gallic acid as substrate.

Função bioquímica da via daslipoxigenases em plantas de soja submetidas ao ataque de mosca-branca (Bemisia argentifolii)

Neste trabalho, avaliou-se a capacidade da planta de soja de uma cultivar comercial, IAC-100, e de um genotipo IAC-100 TN que apresenta ausencia de lipoxigenases nas sementes de responderem ao ataque de mosca-branca (Bemisia argentifolii) pela via das Lipoxigenases. Foi realizada a caracterizacao cinetica do pool de lipoxigenases. Os valores de KMapp decresceram nas plantas atacadas, sugerindo uma alteracao no pool de lipoxigenases foliares. Valores similares de KMapp, entre os genotipos, indicam que a remocao de lipoxigenases de sementes nao interferiram na expressao de lipoxigenases em folhas. Ocorreu aumento significativo na producao de inibidores de proteases. Com esses resultados, infere-se que a producao de inibidores de proteases esta envolvida no mecanismo de defesa de soja ao ataque da mosca-branca.

Resistance to stem canker, frogeye leaf spot and powdery mildew of soybean lines lacking lipoxigenases in the seeds

A cultura da soja [Glycine max (L.) Merrill] ocupa lugar de destaque na economia brasileira, tanto em termos de area plantada, quanto de producao de graos. A presenca de gosto de feijao cru tem sido limitante para o consumo de derivados de soja pelos povos ocidentais. Esse sabor caracteristico e proporcionado pelas enzimas lipoxigenases (Lox1, Lox2 e Lox3). A eliminacao dessas enzimas, pela manipulacao genetica dos alelos que as codificam, e a maneira mais adequada de contornar os problemas associados ao sabor desagradavel. Visando elucidar a participacao das lipoxigenases, no processo de resistencia da soja a patogenos, variedades normais de soja (FT-Cristalina RCH, Doko RC e IAC-12) e suas respectivas linhagens obtidas por retrocruzamentos, sem as tres lipoxigenases nas sementes (triplo-nulas - TN) e com as tres lipoxigenases (triplo-positivas - TP), foram testadas quanto as suas resistencias ao cancro-da-haste (Diaporthe phaseolorum f.sp. meridionalis), a cercosporiose (Cercospora sojina Hara) e ao oidio (Microsphaera diffusa Cke. & Pk.). Todos os materiais geneticos foram resistentes ao cancro-da-haste. Com relacao a cercosporiose, FT-Cristalina RCH e Doko-RC e suas respectivas linhagens com ou sem lipoxigenases mostraram-se resistentes, enquanto IAC-12 e suas linhagens derivadas mostraram indices de doenca mais elevados, sendo que as linhagens IAC-12 TP e TN foram mais suscetiveis, indicando perda de gene de resistencia nos retrocruzamentos. Nao houve relacao entre retirada dos genes que codificam lipoxigenases nas sementes com a resistencia a cercosporiose. No caso do oidio, as linhagens TP ou TN apresentaram-se similares ou pouco mais resistentes que seus respectivos progenitores recorrentes, os quais se mostraram suscetiveis na seguinte ordem: IAC-12, menos suscetivel, Doko-RC, intermediario e FT-Cristalina RCH, mais suscetivel.

Trypsin activity in chyme of Thai tilapia submitted to different water temperatures

The objective of this study was to evaluate the enzymatic activity of trypsin in the intestinal content of the Thai tilapia male submitted to four different water temperatures. Fingerlings with 0.835 ± 0.004 g initial body weight were distributed in fishbowls with temperatures of 20, 24, 28 and 32oC. They were fed the same diet and maintained under these conditions until the 55th day of the experiment. The tilapias were removed from the fishbowls and immediately placed on ice for death and to halt the enzymatic activity. The middle and posterior intestines were removed and placed in 2 mL polyethylene flasks. The samples were centrifuged to determine the trypsin activity in the supernatant by using N-Benzoil-D, L-arginina p-nitroanilida (D,L-BApNA) as substrate -and later reading in an optical spectrophotometer. Male Thai tilapia submitted to 32oC increased tripsin activity and decreased specific tripsin activity.

The Rolling of Food by Dung Beetles Affects the Oviposition of Competing Flies

Flies are the main competitors of dung beetles for oviposition sites and rolling dung beetles relocate their food to reduce interspecific competition. Furthermore, dung beetles deposit chemical substances on the food ball that may repel fly larvae and certain predators. In the present study, using Deltochilum furcatum, a dung beetle that does not exhibit parental care and the blow-fly, Lucilia cuprina, we tested the hypothesis that pygidial secretions deposited on the food ball could also make it less attractive as an oviposition site for flies. Food balls rolled by either D. furcatum males or females received significantly fewer eggs that balls that had not been rolled by beetles. Also, flies laid significantly fewer eggs on food balls treated with secretions collected from male pygidial glands. Reduced fly oviposition may be a direct effect of compounds the beetles deposited, acting as an allomone, and/or an indirect negative effect on the microbial community that stimulates fly oviposition. A model of the reproductive biology of this species is proposed.