EFFECT OF FOOD SUPPLY IN BOTH FOOD QUALITY AND QUANTITY ON THE POPULATION DYNAMICS OF BRACHIONUS URCEOLARIS

The effect of food quality on the population dynamics of B. urceolaris was studied at temperature of 26±1℃ and food concentration of 0.3mg/ml. Rotifers were cultured individually and fed on Chlorella ellipsoidea, Scenedesmus acuminatus or a 1:1 mixture (wet weighty) of these two algae. There were no significant differences in embryonic developmental times and mean lifespans with the type of diet.Rotifers fed on C. ellipsoidea had the shortest pre-reproductive and postreproductive periods, the longest reproductive periods, the highest reproductive rate, and the increasing number of eggs and intrinsic rate of population. Among the three types of diet,C.ellipsoidea was the best for the growth of B. urceolaris population.The effect of food quantity on the population dynamics of B. urceolaris was also studied in replicated individual cultures at temperature of 23 ±1℃ and at five concentrations (0.375, 0.75, 1.5, 3.0 and 5.0 ×106 cells/mL) of C. ellipsoidea. The lowest food concentration at which the rotifer survived and reproduced was 0.75×106cells/mL. There were no significant differences in embryonic developmental times and post-reproductive periods at different food concentrations, nor were the duration of principal developmental stages and the number of eggs at the food concentrations of 1.5 ×106 cells/mL and 3.0 ×106 cells/mL. The rotifers had shorter mean lifespans and produced fewer eggs when fed with the algae concentration of above 3.0 ×106 cells/mL or below 1.5 ×106 cells /mL; At the food concentration of above 3.0×106 cells/mL,the rotifers had shorter reproductive periods. The rotifers fed on the algae at the concentration of 3.0 ×106 cells/mL had the highest reproductive rate. Net reproductive rate and intrinsic rate of population increased among all the food concentration. The population growth of the rotifer was better at the food concentration from 1.5×106cells/mL to 3.0×106 cells/mL, and 3.0 ×106cells/mL was the best food concentration.