Use of microalgae bioencapsulated in Artemia during the weaning of Senegalese sole (Solea senegalensis Kaup)

The microalgae species Chlorella minutissima and Tetraselmis chuii were bioencapsulated in Artemia metanauplii and used during the weaning of Senegalese sole, Solea senegalensis post-larvae. We evaluated the effect of microalgae on: (i) survival and growth of the Senegalese sole post-larvae and juveniles, (ii) expression of genes related to the non-specific immune system, and (iii) the microbial load of sole juveniles. The survival of sole juveniles at the end of the experiment was significantly higher in the treatments added microalgae in their diet compared with the control treatment (P < 0.05), while there was no effect on the final weight of sole juveniles. The total numbers of bacteria as determined by the counts on Zobell's medium were significantly lower in both treatments added microalgae compared with the control treatment (P < 0.05), whereas no significant differences were shown among the different treatments in the numbers of presumptive Vibrio as determined by counts on TCBS. Four partial nucleotide sequences of genes related to the immune system were isolated from lymphoid tissues of S. senegalensis: natural resistance associated macrophage protein 1 (Nramp1), complement C3, transforming growth factor beta 1 (TGF-beta 1), and transferrin. The expression of these four genes was calculated at the end of the experiment in relation to the expression of beta-actin, a housekeeping gene. No significant differences (P > 0.05) were determined among the three treatments in relation to the expression of the four genes in homogenates of fish. (C) 2009 Elsevier B.V. All rights reserved.