Factors determining nutritional quality in Artemia nauplii.

Aquaflow Technical Leaflet 2003-116

European Network for the Dissemination of Aquaculture RTD Information (Q5CA-2000-30105) and previously FAIR-3837, URL: http://www.aquaflow.org/

Nauplii of the brine shrimp Artemia constitute an essential larval food source in the first feeding of cultured marine species. The reproductive mechanisms and nutritional characteristics of Artemia were studied with the objectives of developing enrichment protocols, to optimise nutritional quality.

Oviparity occurs when, under extreme conditions, embryos only develop up to the gastrula stage and enter a state of dormancy (diapause) before being released by the female (the ‘cysts’). The mechanism is strongly dependent on low food availability, although a genetic effect seems to exist. Furthermore, parthenogenic (adults developed from a non-fertilized egg) tetraploid populations also show high oviparity levels.  Ovoviparity is the reproduction in which fertilised eggs develop normally into free-swimming nauplii, which are released by the female.

With regard to nutritional quality, differences have been found in the lipid composition of the “benthic mat” (the superficial layer of the saline sediments) and in the halophilic (‘salt-loving’ bacteria compared to that found in planktonic microalgae (typically used in aquaculture). This has led to studing the influence of typical bacterial and phytoplanktonic flora on the levels of polyunsaturated fatty acids (PUFA) in biomass and cysts of Artemia.

Artemia populations found in continental (freshwater) lagoons typically have low levels of PUFA in their cysts and nauplii. However, it has been found that some of these populations have PUFA levels similar to those originating in coastal lagoons (of marine origin and generally containing higher levels of the essential fatty acid, EPA and traces of DHA). Therefore, it is not correct to associate low lipid levels to origin. Both the culture conditions and the diversity of the lagoon flora have a profound effect on the fatty acid profile of Artemia cysts and a further genetic influence cannot be discarded.

In order to develop alternative enriching techniques to supply nutrients to Artemia nauplii, liposomes containing high levels of PUFA were prepared. In this study, three types of liposome were used. Those made up of highly unsaturated phospholipids and capable of transporting hydrosoluble substances were the most effective. Phospholipids extracted from krill and cholesterol were found to be effective in meeting the enrichment requirements of Artemia nauplii. Nevertheless, it is convenient to use liposomes combining high levels of unsaturated phospholipids together with a high stability in transporting hydrosoluble susbtances.

For more information:

Dr. F. Amat 
CSIC
Instituto de Acuicultura de Torre de la Sal
12595 Ribera de Cabanes.
Castellón - Spain
Tel.: +34 964 319500
Fax.: + 34 964 319509
E-mail: amat@iats.csic.es

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