Nutrition of the sea urchin Paracentrotus lividus (Echinodermata: Echinoidea) fed different artificial food

Nutrition and growth of 3 size classes of Paracentrotus lividus fed different artificial diets were studied at monthly intervals over 9 mo. At the end of the experiment, the gonadal, test and gut growth rates were estimated so as to establish nutritional budgets. Three types of food were provided: 'vegetable-feed' (low protein, high carbohydrate), 'mixed-feed' (intermediate protein and carbohydrate) or 'animal-feed' (high protein, low carbohydrate). Nutritional parameters were affected by food quality, sea urchin size and experimental period. The highest ingestion rate was obtained with the vegetable food. The highest absorption value was recorded with the animal food while the lowest was observed for the vegetable food. Absorption was negatively correlated to both ingestion rate and carbohydrate levels of the food. The assimilation efficiency was lowest with the vegetable diet and highest with the animal-based feed. Allocation of energy amongst the different body organs was influenced by food quality and sea urchin size. A growth model based on the results shows that sea urchin growth can be explained by 4 factors: the quantity of food ingested; the amount of food absorbed; the size of the individuals; and the quantity of dry matter absorbed.