Effects of diet on population development of the rotiferBrachionus plicatilis in culture

Experiments were conducted in order to observe the effect of five diets on the population development of the rotiferBrachionus plicatilis Müller under laboratory conditions. Diets were based on baker’s yeast (Saccharomyces cerevisiae) and the algaeTetraselmis suecica andIsochrysis galbana, mixed, or as simple diets. Growth rates, fecundity and biometric parameters were studied for 15 days. The cultures were divided in a logarithmic phase and a harvesting phase. Rotifers fed onTetraselmis, alone or mixed with yeast orIsochrysis, gave good performances with the best results in all the parameters studied. Average growth rates in all diets were similar during the exponential phase, with values ranging from 0.72 (Tetraselmis andTetraselmis + yeast) to 0.47 (yeast). During the harvesting phase there were high differences between diets, with rates highly reduced in the yeast-group (0.17) and good rates whenTetraselmis was ingested (0.65–0.51). This alga had a positive influence on the rotifers, increasing individual growth and fecundity.