| Resumo: |
The utilization of the energy of food by red porgy (Pagrus pagrus Linnaeus, 1758) from the Argentine Sea (SW Atlantic) was studied. From the energetic point of view, it is proposed that the strategy of patitioning, utilization and storage of the energy of food, is an indicator of the organism response to the environmental conditions. The main objective was to know the proportion of the energy of food derived to the different components of the bioenergetics budget. In order to estimate the monthly energy investment in reproductive growth, chemical analysis of gonads from fishes caught by the fishery fleet and from laboratory studies were performed. Two indexes were used to calculate the energy investment in female ovaries: the proportion of net daily energy change in the ovaries in relation to the food consumed (effort), and the reproductive cost. During December and January, the spawning time in the broodstock tank was 16:00. Energy storage and stable periods were detected along the year in the wild fishes. The energy content in the ovaries significantly increased from June. The estimation of reproductive effort showed that approximately the same proportion of the energy from food was deposited in the ovaries between March and June. The annual percentage of energy from food derived to the ovaries was estimated in 12.3%. Results from larval studies indicated that hatching is a critical event, in which morphological and physiological changes overlap. The shift from endogenous to exogenous feeding is another important moment in the life of larvae, in which changes in body composition were detected as a consequence of the transformation of yolk into body tissue or energy. Lipids from oil globule were the dominant aerobic fuel for red porgy larvae from day 1, time after hatching (TAH). Newly hatched larvae use preferebly carbon-rich compounds, mainly lipids, but only when yolk reserves exhosts, lipids and proteins are fueled or deposited at a similar rate. Oxygen consumption in larvae showed an isometric change in relation to the weight, so the consumption rate is considered almost independent from body size at this time of the development. The strategy of endogenous energy utilization of larvae during the first 3 days of life clearly showed the priority assigned to the organogenesis. This process must prepare individuals for the starting of exogenous feeding.
Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales.
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