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Fluorospheres for Studying Food Intake, Selectivity in Sea Bass Larvae

31 May 2013

PORTUGAL - In the XIII Congress of the Iberian Society of Cytometry held in Aveiro (Portugal) last May, the Institute of Biomedical Research of the Arnau de Vilanova University Hospital (UdL) and IRTA, presented a new alternative method for assessing food intake and selectivity with radioactive isotopes.

The method is based on the marking of the live food with fluorospheres (FLEsf) and performing counts using flow cytometry (FC).

The results showed applicability of the method in studies on the selection of live preys (Artemia) in the feeding of fish larvae (sea bass).

Fish larvae were fed 30 days after hatching with three types of enriched Artemia marked with fluorospheres. Artemia enriched with Nannochloropsis (live microalgae), Easy Selco DHA mixed with live oil (lipid emulsion), and Easy Selco DHA (lipid emulsion) were marked blue-green, blue, and yellow-green fluorospheres, respectively. The omega-3 fatty acid content was very different in the three types of Artemia.

The following day, marked Artemias (with spheres) and larvae that had eaten Artemia were collected. Sample tissues were digested to assess the intake either by FC or measuring fluorescence in a spectrophotometer.

On Day 31 the same protocol was followed but changing the colors of the fluorospheres that marked the Artemias of the diet groups.

Researchers involved in the study believe preliminary results look very promising, with a significant correlation between the values obtained by FC and fluorometry. Under laboratory conditions, sea bass larvae do not choose the Artemia used in this study in their diet.

Regarding the used fluorospheres, the researchers pointed out that better results were obtained with yellow-green fluorospheres in comparison with other methods, while with blue fluorospheres the intensity with fluorometry is lower. To optimize the methods the number of fluorospheres spheres should be increased and alternatives to the blue spheres should be used.

In brief, the presented method provides relative results on the intake of different types of food, allowing the possibility of other type of studies to determine if there is preference to a specific type of food. It is also a new option for using FC in nutritional studies.

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