Larval ontogeny of the digestive system of red scorpionfish Scorpaena scrofa Linnaeus, 1758: histological aspects

This study describes, for the first time, larval growth stages of red scorpionfish, Scorpaena scrofa (Linnaeus, 1758) from 0 until 63 days post hatching (DPH) in order to provide information about organogenesis. Moreover, it could constitute a first step toward the determination of the functional capabilities of the larvae and, consequentially, their rearing needs. Based on the main morpho-histological characteristics, four main stages have been established: lecitotrophic (0-1 DPH), lecitoexotrophic (2-4 DPH), exotrophic I (5-19 DPH) and exotrophic II (20-63 DPH). Scorpaena scrofa larvae use exclusively the endogenous reserves as energy source until first day. At the same time, the other organs appear as clusters of undifferentiated cells or anlage. During stage II, the yolk sac it is reabsorbed, and mouth and anus open outwards. At this stage, the energy needs is satisfied by endogenous reserves and exogenous nutrition. Therefore, even the structures that, directly and indirectly, support the exogenous feeding (hepatocytes, pancreatic cells, gall bladder) increase their specialization. The energy that is provided from food, is used for an intense organogenesis and for a strong specialization of organs that characterize the third stage of larval development. From stage IV onwards, most organs and structures essentially appear in their final morphology and increase exclusively in size.