Protein depletion of the rotifer Brachionus plicatilis during starvation

During the cultivation of marine fish larvae, unconsumed rotifers (Brachionus plicatilis) may reside in the tanks for several days and their nutritional value may become severely reduced. In order to quantify this process, body biomass and protein content per individual rotifer was measured during starvation at different temperatures (4-28 degrees C) for a period of 5 to 7 days. Both well-fed rotifers and poorly-fed rotifers were used, in order to examine the effect of the nutritional status at the start of the experiment on the loss rates of biomass and protein. At high temperatures the carbon, nitrogen and amino acid content decreased exponentially with time. A large part of body biomass (40-50%) was lost during the first 4 days of starvation at 18-20 degrees C. The rate of decrease was positively related to the temperature. Poorly-fed rotifers were more sensitive to starvation than well-fed rotifers, as their nitrogen content decreased at a higher rate. Starvation of rotifers may be prevented by addition of microalgae in concentrations of 1-2 mg C 1(-1). At 4-5 degrees C, the carbon, nitrogen and amino acid content remained relatively stable. Rotifers may thus be stored for <5 days at 4-5 degrees C without a significant loss in their nutritional value. (C) 1999 Elsevier Science B.V. All rights reserved.