The effects of dietary arachidonic acid on bone in flatfish larvae: the last but not the least of the essential fatty acids

Abstract

Flatfish can provide a reliable model to study developmental disorders in bone tissues occurring during morphogenesis in response to nutritional imbalances. To date, most studies dealing with the effect of dietary essential fatty acids (EFA) on skeletogenesis in fish have focused their investigation on the role of docohexanoic (22:6n−3, DHA) and eicosapentaenoic (20:5n–3, EPA) acids, but only a few have focused on investigating the effects of arachidonic acid (20:4n–6, ARA) on bone during fish larval development. Bone development and composition at larval stage have been demonstrated to be highly sensitive to dietary levels of EFA, in particular the EPA and ARA acids, both precursors for highly bioactive eicosanoids presenting opposite effects on bone metabolism. Since fish are not able to synthesize EFA, they need to obtain them from the diet. However, dietary imbalances in EPA and ARA in flatfish larvae may disrupt bone formation and osteoblast differentiation in skeletal tissues, leading to the incidence of skeletal deformities, reduced mineralization and problems of bone remodelling in the cranial region associated with impaired eye migration. These anomalies in skeletal structures are one of the most important factors that affect flatfish larval quality and hamper their production. Thus, we have reviewed the current state of knowledge about the effects of dietary ARA contents on skeletogenesis in Senegalese sole (Solea senegalensis), one of the main flatfish species cultured in Europe. Their larval quality still suffers for a high incidence of skeletal anomalies induced by dietary imbalances during metamorphosis.