Growth and fatty acid composition of juvenile Cerastoderma edule (L.) feb live microalgae diets with different fatty acid profiles

The importance of dietary 20:5n-3 (EPA), 22:6n-3 (DHA) and 20:4n-6 (ARA) for growth, survival and fatty acid composition of juvenile cockles (Cerastoderma edule) was investigated. Cockles of 6.24 +/- 0.04mm and 66.14 +/- 0.34mg (live weight) were distributed into three treatments where live microalgae diets were fed constantly below the pseudofaeces production threshold, for three weeks. Diets had distinct fatty acid profiles: high EPA (53% Chaetoceros muelleri+47% Pyramimonas parkeae), no DHA (47% Brachiomonas submarina+53% Tetraselmis suecica) and low ARA concentrations (73% P.parkeae+27% Phaeodactylum tricornutum). Growth was positively affected by high EPA and low ARA diets, whereas no significant growth was observed for the no DHA diet. High mortality of cockles fed no DHA diet raises questions about its suitability for cockles. In balanced diets with EPA and DHA, lower concentrations of ARA do not limit growth. The impact of dietary fatty acids was evident in the fatty acids of neutral and polar lipids of cockles. In polar lipids of all cockles, there was a decrease in EPA, in contrast to an increase in DHA. The combination of EPA and DHA in a live microalgae diet was beneficial for the growth and survival of juvenile cockles.