The effect of diet type on growth and fatty-acid composition of sea urchin larvae, I. Paracentrotus lividus (Lamarck, 1816) (Echinodermata)

This study investigated the growth and fatty acid composition of the sea urchin larvae Paracentrotus lividus fed on four types of diets: the microalgae Dunaliella tertiolecta, two types of microencapsulated formulated feeds and a concentrated algal paste. The larvae were successfully raised to metamorphosis on three diets, including the microalgae and the two formulated feeds. No significant difference was found in survival rate and metamorphosis rate for larvae fed with microalgae, formulated feeds, or microalgae plus formulated feeds. The fastest growth rate was obtained for larvae fed with microalgae, while normal growth and survival were only achieved for larvae fed with formulated feeds at a high frequency feeding rate. Normal larval development was not supported by either of the formulated feeds at a low feeding rate. A concentrated algal paste was also used for the low ration experiment, but failed to support any larval growth. Post-larval development was better for larvae fed on the formulated feeds, presumably reflecting the nutritional value of these feeds. P. lividus larvae grew well on D. tertiolecta which had a relatively low content of protein (37% dry weight) and lipid (7% dry weight). The larvae could assimilate highly unsaturated fatty acids (HUFAs) such as DHA, EPA and ARA from the diet, or synthesize them from linoleic acid 18:2 n-6 and linolenic acid 18:3 n-3. They could also biosynthesize non-methylene-interrupted-dienoic fatty acid NMID 20:2 de novo when feed on D. tertiolecta and the formulated feeds. An accumulation of PUFA n-3 may improve larval growth. P. lividus larvae showed the tendency of food selection towards D. tertiolecta, and a better formulated feed with additives or attractants will give a better performance in larval growth.