Amino acid pools of rotifers
and Artemia under different conditions: nutritional implications for
fish larvae
C. Aragão, L.E.C. Conceição, M.T. Dinis, H.-J.
Fyhn-2004
Aquaculture, 234(1-4): 429-445
Abstract:
The rearing of most marine fish species still relies
on live food. Amino acids (AA) are the building blocks for protein
synthesis, are important energy substrates, and are involved in specific
physiological functions. Thus, the AA pools (free and protein-bound) of the
rotifer Brachionus rotundiformis and of Artemia parthenogenetica
metanauplii were analysed, after enrichment with different diets or at
different salinities. The changes in these pools were related to their
impact when used as feed for the developing fish larvae. Rotifers and Artemia
were enriched for 24 h in microalgae, in commercial diets, or starved for
the same time period. The enrichment at different salinities was also tested
using Artemia. The free AA (FAA) quantity and quality was strongly
affected by the enrichment used, in both rotifers and Artemia
metanauplii. The relative FAA content was significantly higher in rotifers
and Artemia enriched with microalgae than in the ones enriched with
commercial products, and between the different microalgae tested, the
enrichment in T. chui resulted in the highest FAA content for both
preys. Differences regarding the FAA quantity and quality were also found
between rotifers and Artemia. With the exception of the starved
preys, a higher relative FAA content was found in rotifers than in Artemia
metanauplii and while the FAA pool of the rotifers was dominated by alanine,
taurine was the dominant AA in the FAA pool of Artemia. Salinity had
only a small effect on the FAA pool of Artemia. Concerning the
protein fraction, starvation increased the relative protein content in the
rotifers. Among the metanauplii, the relative protein content was affected
neither by the enrichment nor by salinity, except for a significantly lower
content found when the microalgae Nannochloropsis gaditana was used.
The quality of the protein pool is affected by the different enrichments,
but not by salinity. However, the changes in the protein-bound AA pool were
less pronounced than for the FAA pool and reflect differences in the protein
content and/or quality of the diet. This study showed that the AA
composition of cultured zooplankton is affected by feeding regime and by
salinity. The choice of the best zooplankton enrichment and/or mixture of
enrichments for the different fish larval stages, should take into account
the AA composition, in order to fulfil the energetic and nutritional
requirements of the larvae.
(CCMAR, Universidade do Algarve, Campus de Gambelas,
8000-117, Faro, Portugal, e-mail: caragao@ualg.pt)