An evaluation of dietary lipids on growth performance in the sea urchin, Lytechinus variegatus (Echinodermata: Echinoidea)

Sea urchin fisheries are declining across the world, and sea urchin aquaculture will be an important alternative to wild-caught fisheries. A significant aspect of a successful sea urchin culture operation is the formulation of nutritionally-complete diets with the potential to support optimal growth and health to sea urchins at different life stages. Due to the ecological variety of sea urchin species, the inclusion level and source of the various macronutrients and micronutrients needed for a complete diet must be carefully considered for each sea urchin species.;Lytechinus variegatus is an echinoid species commonly found in the northern Gulf of Mexico, and it is often used for biomedical and ecotoxicological research. Whereas dietary protein requirements for L. variegatus have been evaluated in numerous studies, the quantity and quality of dietary lipids needed to ensure provision of energy for protein sparing and essential fatty acids are not known. Increasing costs and perceived decrease in availability of historical dietary lipid sources, such as fish oil, have led researchers to consider plant oil alternatives for formulated diets, but their effectiveness supporting growth many species, including L. variegatus, is not known.;Dietary lipids from phospholipids, cholesterol, menhaden oil, or soybean oil were evaluated for juvenile, small adult, and adult L. variegatus using semi-purified and purified diets. Total dietary lipid levels ranging from 5.6 to 9.0% supported the best growth for all life stages studied, and high total lipid levels (>11%) or diets containing soy oil reduced growth for all life stages evaluated. Low lipid levels (ca. 5.6%) supported best growth for juveniles. Levels of dietary cholesterol evaluated did not affect growth in small adults. High dietary lipid levels resulted in higher lipid levels in the gut tissue than those found in wild population, suggesting a pathological response. The purified diet containing a combination of low levels of menhaden oil and soybean oil supported 65% of the weight gain of that for individuals fed a semi-purified diet and may be considered for future nutritional evaluation for sea urchin diets.;Keywords: sea urchin, dietary lipids, menhaden, soy, phospholipid, formulated diet...