The population growth of the rotifer, Brachionus plicatilis cultured with a marine species of Chlorella suspended at various densities was investigated.
Experiments were performed by culturing many individuals in many test tubes each containing two individuals in the experimental medium. From daily counts of eggs laid and surviving individuals, time intervals from hatching to 50% survival and to peak of fecundity, net reproduction rate, intrinsic rate of population increase and mean generation time were estimated.
The results obtained are summarized as follows.
1. The values of the indices concerning population growth of the rotifer indicate that for its mass production the marine Chlorella should be kept always at the density of 85-213×10⁴ cells/ml, where 150 ×10⁴ cells/ml may be the most desirable because of the highest values of intrinsic rate of population increase and net reproduction rate.
2. Population growth of the rotifer can be restrained in Chlorella suspension even at the density (less than 213×10⁴ cells/ml) where the rotifer can not reach a satiated condition.
3. The weight and volume of the Chlorella were estimated at 7.1×10^-6μg and 1 ×10^-8mm³ per average cell, respectively. Therefore, the most suitable density for population growth of the rotifer is estimated as 10.7μg/ml or 1.5×10^-2mm³/ml.