The effect of glycerol dissolved in the rearing water on the transition to exotrophy in gilthead sea bream Sparus aurata larvae

The effects of glycerol added to seawater at different concentrations were tested in monocultures of Chlorella minutissima and Brachionus plicatilis in mixed cultures of these two species and on starved or fed Sparus aurata larvae. Glycerol enhanced the growth of Chlorella and seemed to indirectly benefit the rotifers that feed on it. Its beneficial effect on gilthead sea bream prelarvae and larvae resulted in glycogen accumulation in the liver and absence of signs of cholestasis-like pathology. This effect varied according to the glycerol concentration in the water, to its addition timing and to light and feeding conditions. The gluconeogenic origin of the hepatic glycogen reserves is discussed, together with the mediating role of the food chain in glycerol larval assimilation.