Fundamental Studies on Physiology of Rotifer for its Mass Cultrure-II

The influence of the water temperature on the population growth of the rotifer, Brachionus plicatilis, was investigated by culturing many individuals separated one or two into test tubes. The time intervals from hatching to 50% survival and to peak of fecundity, net reproduction rate, intrinsic rate of population increase and mean generation time at various temperatures were estimated from the daily counts of eggs laid and surviving individuals. The present study aimed to find the most suitable temperature for mass production of the rotifer from the values of these indices. The results obtained are summarized as follows. 1) The intrinsic rate of increase shows a highest value of 0.91 at 27°C. Therefore, if estimating only from the intrinsic rate, the most desirable temperature for the increase in the rotifer's population might be 27°C. However, the values of other indices indicate that the temperature of 27°C may be near the limit for the natural growth of the rotifer. Hence, it is speculated from the results of the present experiment that the most desirable temperature for actual mass production of the rotifer is about 25°C. 2) The physiological activity of the rotifer is influenced by the culture conditions, experienced by its parents and during its egg stage. Therefore, the rotifer cultured under inadequate conditions can not recover to a state of natural growth immediately after improvement of the condition.