Studies on the Formation and Hatching of Fertilized Eggs of the Rotifer Brachionus plicatilis-VI. Use of Preserved Diet for Rotifer Brachionus plicatilis Resting Egg Formation.

Abstract

The reduction of environmental water exchange and the supply of an ample amount of diet are required for inducing rotifer resting egg formation. The use of a preserved diet is essential for conducting trials of mass formation of resting eggs in a large scale tank. The potential for applying preserved diets for L-and S-type rotifer Brachionus plicatilis resting egg production was investigated in the laboratory. Dietary values of frozen or refrigerated diets (baker's yeast, Chlorella vulgaris, Euglena gracilis, and Nannochloropsis oculata) in condensed forms were compared with fresh N. oculata diet (control).Frequencies of rotifer mastax movement when fed most of the preserved diets were equal with the control. In the individual culture experiment, growth and mixis rates obtained by feeding preserved diets were much less than the control. Growth rates increased to the level of the control, however, when tested diets were fed to batch-cultured rotifers in a 20l medium. The remarkable increase of mixis rates in batch cultures was observed when preserved diets were fed to S-type rotifers. The number of resting eggs formed from 1g dry weight preserved diet was 7.8-112.0 (×103) and 2.1-5.0 (×103) for L-and S-type rotifers, respectively. Meanwhile, it was 138.0 for L-type and 15.4 for S-type with the control diet.