[en] The use of lysed microalgae in the diet of carnivorous fish can increase the bioavailability of proteins and bioactive compounds, such as unsaturated fatty acids or vitamins in the digestive tract. These are essential molecules for the proper physiological development of fish in aquaculture. However, some antinutritional components and other undesirable molecules can be released from an excess of microalgae supplied, compromising the integrity of the intestine. The inclusion of small amounts of hydrolized microalgae in the fish diet can be a good strategy to avoid negative effects, improving the availability of beneficial compounds. Nannochloropsis gaditana is an interesting microalgae as it contains nutraceuticals. Previous studies reported beneficial effects after its inclusion in the diet of Sparus aurata, a widely cultured species in Europe and in all Mediterranean countries. However, administration of raw microalgae can produce intestinal inflammation, increased intestinal permeability, bacterial translocation and disturbance of digestion and absorption processes. The aim of this study was to evaluate changes in the intestinal microbiota and barrier stability of S. aurata fed with low inclusion (5%) hydrolysed N. gaditana. Intestinal microbiota was analyzed using Illumina MiSeq technology and libraries were constructed using variable regions V3–V4 of 16S rDNA molecules. Analysis were based in the identification, quantification and comparison of sequences. The predictive intestinal microbial functionality was analyzed with PICRUSt software. The results determined that the intestinal microbiota bacterial composition and the predictive intestinal microbiota functionality did not change statistically after the inclusion of N. gaditana on the diet. The study of gene expression showed that genes involved in intestinal permeability and integrity were not altered in fish treated with the experimental diet. The potential functionality and bacterial taxonomic composition of the intestinal microbiota, and the expression of integrity and permeability genes in the intestine of the carnivorous fish S. aurata were not affected by the inclusion of hydrolysed 5% N. gaditana microalgae.

[es] El uso de lisados de microalgas en el cultivo de peces carnívoros puede aumentar la disponibilidad de compuestos bioactivos en el tracto digestivo, mejorando su desarrollo y bienestar. Sin embargo, un exceso de microalgas en la alimentación puede generar algunos componentes antinutricionales, comprometiendo la integridad del intestino. Nannochloropsis gaditana es una microalga interesante, pues contiene compuestos nutracéuticos, aunque su administración en crudo produce inflamación intestinal y cambios en la comunidad bacteriana del intestino, produciendo desequilibrios digestivos y de absorción. En el presente trabajo se han evaluado cambios en la estabilidad y diversidad de la microbiota intestinal de la dorada (Sparus aurata) alimentada con hidrolizados de N. gaditana al 5% de inclusión en el pienso. La microbiota intestinal se analizó mediante secuenciación masiva de ADN ribosómico, mientras que la funcionalidad de la barrera intestinal se evaluó mediante expresión de ciertos genes asociados a esta función. Los resultados muestran que no existen cambios significativos ni en la microbiota ni en la integridad intestinal debidos a la inclusión en la dieta de hidrolizados de N. gaditana al 5 %. Por lo tanto, el presente estudio muestra la posibilidad de complementar la dieta de dorada con hidrolizados de microalgas para mejorar la disponibilidad de compuestos bioactivos.