Effect of dietary vitamin C level during early larval stages in Senegalese sole (Solea senegalensis)

The aim of this work was to assess the effects of a dietary supplement of vitamin C (as ascorbyl palmitate, AP) delivered through new and optimized alginate microcapsules (MA) on larval performance, antioxidant status and gene expression profiles. For this purpose, three MA (referred to as MA-1, MA-2 and MA-3) with increasing AP content ranging from 1700 to 5700μg AP g−1 DW were assayed. Sole larvae were fed the three MA from first feeding to 7days post-hatch (dph) and later replaced by Artemia from 7 to 28 dph. The experimental groups were performed in triplicate using a recirculation system. The efficiency of AP inclusion into MA was 55%. At 7 dph, larval ascorbic acid (AA) content was proportional to the AP concentration included in MA (p<0.05). Larval growth until 7 dph was low but significantly higher in larvae fed MA-2 and MA-3. After Artemia supplying, a compensatory growth was detected in the three experimental groups whereas a faster metamorphic process and a higher weight at 28 dph in larvae fed MA with a higher AP content (MA-2 and MA-3) was observed (p<0.05). Moreover, Artemia feeding substantially increased the larval AA content during development peaking at 18 dph and decreasing at the end of metamorphosis with significantly lower AA levels in larvae fed MA-3. This reduction coincided with a higher total antioxidant capacity and lipid peroxidation whereas no differences in catalase or total glutathione peroxidase were detected. Expression data revealed that MA diets significantly modified the transcript levels of 16 genes involved in antioxidant defence (gpx1), tissue structure (col1a1 col1a2 and col1a3), stress (hsc70-1, hsc70-2, hsc70-3, gr1, gr2, pomcb), glycolytic pathway (gapdh1 and pkm), osmoregulation (cftr, nkcc2 and nkcc1) and pigmentation (mc1r). All these data reveal novel new insights about role of vitamin C during early stages of S. senegalensis to modulate growth, stress and antioxidative status in later developmental stages.