Effects of temperature on performance and morphometry of tilapia, Oreochromis niloticus, of Thai lineage

Um ensaio, com duração de 55 dias, foi realizado no Laboratório de Nutrição e Produção de Peixes do Departamento de Zootecnia da Universidade Federal de Viçosa, MG, com o objetivo de verificar os efeitos da temperatura sobre o desempenho produtivo, por meio de índices zootécnicos, e na morfometria de tilápias de linhagem tailandesa, na fase juvenil. Os peixes, provenientes de um criatório comercial, com tamanho inicial de 0,835 ± 0,004g, foram distribuídos em 24 aquários com capacidade para 100l cada com aquecimento e aeração suplementar. O delineamento experimental foi inteiramente casualizado, composto por quatro tratamentos, correspondentes às temperaturas-teste: 20,0; 24,0; 28,0 e 32,0º C; seis repetições e dez peixes/unidade experimental. A ração utilizada, à base de milho, farelo de soja e glúten de milho, continha 29,0% de proteína digestível, 3.000 kcal de energia digestível e 3,44% de fibra bruta. Foram avaliados: o ganho de peso (GP) individual e da biomassa do aquário (GB), o consumo de ração (CRA) e a conversão alimentar (CAA) aparentes, as taxas de crescimento específico (TCE), de eficiência protéica (TEP) e as de deposição diária de proteína e de gordura (TDP e TDG, respectivamente), a composição corporal (teores de matéria seca, proteína bruta e extrato etéreo), os índices hepatossomático (IHS) e hepatovisceral (IHV) e o coeficiente Intestinal (CI), além do fator de condição alométrico (K). O desempenho das tilápias, bem como as relações morfométricas foram influenciados pela temperatura, estando os melhores índices entre 28,0 e 32,0º C. A mortalidade aumentou com a elevação da temperatura, porém nas temperaturas mais baixas, 20,0 e 24,0º C, nas quais a mortalidade foi 0,00 e 1,67%, respectivamente, o desempenho foi significativamente pior que nas temperaturas mais elevadas, o que permite concluir que as tilápias tailandesas, na fase juvenil, apresentam melhor desempenho e morfometria em temperaturas entre 28,0 e 32,0º C.A 55 days essay was accomplished in the Fish Nutrition and Production Laboratory the Department of Animal Science of the Universidade Federal de Viçosa, MG, with the objective of verifying the effects of the temperature on the productive performance, by means of zootechnical indexes and morphometry, of juvenile tilapias of Thai lineage. The fish, from a commercial fish farm, with initial weight of 0,835 ± 0,004 g, were distributed in 24 aquaria with 100l of capacities, with heating and supplemental aeration. The experimental design was entirely casualised, with four treatments, corresponding to test-temperatures: 20,0; 24,0; 28,0 and 32,0º C; six replicates and ten fishes/experimental unit. The used ration, with corn, soybean meal and corn gluten base, contained 29,0 % of digestible protein, 3.000 kcal of digestible energy and 3,44% of gross fiber. It has evaluated: the individual (GP) and the biomass of the aquarium (GB) weight gain, the apparent ration consumption (CRA) and the alimentary conversion (CAA), the specific growth (TCE) and protein efficiency (TEP) rates and the daily protein and of fat (TDP and TDG, respectively) deposition, the body composition (dry matter, gross protein and gross lipids), the hepatossomático (IHS), hepatovisceral (IHV) indexes and the Intestinal coefficient (CI), besides the alometric condition factor (K). The performance of the tilapias, as well as the morphometrics relationships were influenced by the temperature, being the best indexes between 28,0 and 32,0ºC. The mortality increased with the temperature elevation, however in the lowest temperatures, 20,0 and 24,0º C, in which the mortality was 0,00 and 1,67%, respectively, the performance was significantly worse than in the highest temperatures, what allows to conclude that the juvenile Thai tilapia presents better performance and morphometry at temperatures between 28,0 and 32,0º C.Coordenação de Aperfeiçoamento de Pessoal de Nível Superio

Morphological and behavioral development of the piracanjuba larvae

The objective of this work was to study the morphologic development and the swimming and feeding behaviors of piracanjuba larvae, Brycon orbignyanus Valenciennes (1849) (Characiformes, Characidae, Bryconinae), during the period from zero to 172 hours after hatching (standard length = 3.62 - 11.94 mm). The morphological analyses were accomplished by using a trinocular stereo microscope, while the behavioral analyses were performed through periodic observations. In 28 hours after hatching, the larvae (standard length = 6.25 ± 0.13 mm) showed the following structural and behavioral characteristics that made them become active predators able to overcome a larval critical phase, the beginning of exogenous feeding: presence of pigmented eyes, terminal and wide mouth, developed oral dentition, developing digestive tube, yolk sac reduction, fins and swim bladder formation, horizontal swimming, cannibalism, and predation. Intense cannibalism among larvae was verified from 26 to 72 hours. At the end of the metamorphosis - 172 hours after hatching - the larvae measuring 11.94 + 0.80 mm in standard length presented a flexed notochord, caudal fin bifurcation, dorsal and anal fin formation, synchronized movements, and formation of shoals, characteristics that together allow enhanced perception and locomotio in exploration of the environment, determining the best moment for transfering to the fishponds. New studies can contribute to commercial fish farming by improving feeding management, performance, survival, and productivity of this species