Study on the changes of size in Brachionus calyciflorus using different diets

The rotifer Brachionus calyciflorus is one of the very important zooplankton which lives in freshwater that uses algae, protozoa and bacteria of 1-200 µ as food. It will be highly digested in digestive tract of aquatics and the obsorption rate is 97%.Also,its size is smaller than the mouth of aquatics which initiated exogenous feeding where as the highest survival rate was observed in Barbus barbu larvae which consumed Brachionus calyciflorus as the initial food. So, this study investigates on the effects offive different diet treatments including yeast, Chlorella vulgaris, Senedesmus oblquus, (C. vulgaris +S. oblquus) and mixture of(yeast+ C. vulgaris +S. oblquus (on increasing rotifers size. The feeding intensity was 1x106 cells/ml. Water sample was collected from pond no.11 of the Shahid Beheshti hatchery. The rotifers were maintained at stocking density of 50 ind/ml for a period of seven months to acclimatize them to laboratory conditions. Three replicates were used for each treatment. Experiments were carried out in test tubes placed in water baths. The maximum volume of each experimental group was 20 ml and the pH of the medium was 7.6. The density of rotifers in mild aeration was provided and test tubes were exposed to 1000 lux light intensity and 27 º C temperature. The experiment carried out for 10 days. The size of lorica (chitin cover of rotifer) was measured by Biocom visiol software which was connected to camera and Nikon microscope (E-600). The highest difference observed in treatments 1,2 and 5,1. The results indicated the most increase in lorica length, eeg length respeictivly (219.2±5.84 µ), (117.9±2.1 µ) observed in feeding by Senedesmus oblquus and the least increase in lorica length,eeg length respeictivly (189.6±1.17µ), (111.2±1.17 µ) observed in feeding by yeast. In this study, also the lorica area and its egg volume was investigated to determine the relationship between diet and rotifer size and its effect on egg.