Effects of alternative feeds on Paracentrotus lividus broodstock: Asseswesment of egg nutritional composition and larval development

Four alternative feeds, composed of lettuce discards (72 %) and an animal meal (fish, krill, mussel or anchovy discards, 8 %), and a macroalgae-based feed (Laminaria sp. and Ulva sp.), used as control treatment, were tested on Paracentrotus lividus (Lamarck, 1816) broodstock. Adult female were fed for four months, then spawning was induced and obtained eggs were fertilised to analyse the first larval developmental stages. Feed effects were assessed by analysing nutritional composition and fatty acid (FA) profile of the eggs and by analysing larval development. Both evaluations were also conducted on specimens from the natural environment as wild control. Eggs from experimental sea urchins showed similar protein and lipid content, despite the different composition of the experimental diets, while FA profiles reflected feed composition and highlighted differences between wild and farmed sea urchins. Eggs released by wild sea urchins had high concentrations of long chain polyunsaturated FA (LC-PUFA), in detail arachidonic (ARA), eicosapentaenoic and docosahexaenoic acids, while eggs from sea urchins fed lettuce-based feeds had high levels of linoleic and α-linolenic acids. Intermediate products of endogenous biosynthesis pathway for long chain polyunsaturated FA, absent in the tested feeds, were found in experimental eggs confirming the ability of sea urchin to elongate and desaturate PUFA to LC-PUFA. Higher levels of LC-PUFA, notably ARA, were found in the eggs of urchins from the wild. Finally, wild eggs promoted a better larval development, followed by eggs from macroalgae-fed specimens, suggesting that formulated feeds for full-cycle production should include a direct source of LC-PUFA.