Enrichment effect on two Brachionus plicatilis sp. complex morphotypes fed three nutritional enrichment diets

Abstract

Information on effects of different enrichment on different morphotypes within the Brachionus plicatilis sp. complex is limited. This study investigated the effects of different enrichment diets on population growth, fatty acid content and protein content of L and SS types B. plicatilis sp. complex. Three commercial rotifer enrichment formulations were tested: docosahexaenoic acid (DHA) enriched Chlorella vulgaris, frozen Nannochloropsis oculata, salmon roe emulsion oil, against a control diet of normal C. vulgaris. DHA-enriched C. vulgaris and Frozen N. oculata had significantly higher population growth, fatty acid composition and soluble protein in both morphotypes. However, population growth under salmon roe emulsion treatment was affected negatively despite having high essential fatty acid content in both morphotypes. Variations in fatty acid assimilation in non-polar and polar lipids between morphotypes were observed highlighting enrichment effects and possible dissimilar biochemical roles of these compounds in tissue metabolism in each morphotype. Significantly higher levels of soluble protein were detected in DHA-enriched C. vulgaris and control treatment. SS-type had significantly higher soluble protein content except under the frozen N. oculata treatment. Culture method, enrichment type and dosage are important considerations as different rotifer morphotypes respond differently to different enrichment.