Diel food intake and digestive enzyme production patterns in Solea senegalensis larvae

The aim of this study was to examine patterns of food intake and production of the main digestive enzymes of Senegalese sole larvae under a fixed 12 h light:12 h dark cycle. Daily gut content, soluble protein content and digestive enzyme activities were studied at different times of day in pelagic sole larvae (onset of feeding and 6 days post-hatch; dph) and in benthonic sole post-larvae (20 and 30 dph). The larvae displayed temporal changes in food intake throughout development. Pre-metamorphic larvae ceased feeding after lights were turned off. In contrast, post-metamorphic larvae continued to feed during the day, with a higher food intake occurring during dark phase. It was demonstrated that larval digestive enzymes, mainly lipases, were active before mouth opening. Tryptic activity varied with food intake at pre-metamorphic larvae, whereas its activity levels were kept along the day in post-metamorphic larvae.