Effects of crowding signals on population growth of two Brachionus rotifer species

The present work examined the effect of crowding signals on population growth of B. calyciflorus and B. angularis. Culture medium conditioned by rotifers was used as the crowding signals and two crowding levels were set for each rotifer species. Population growth experiments of the two rotifers were carried out at an initial density of 1 ind./mL in 5 ml and 20 ml medium for B. angularis and B. calyciflorus, respectively. Regardless of the treatments, B. angularis reached its maximum population density at 100 ind./mL after 23 days, while it took B. calyciflorus only 3 to 8 days to reach its maximum population density, which was far lower than that of B. angularis. Both B. calyciflorus and B. angularis showed a higher population growth rate (r) and lower maximum population density (K) under the crowding signals of B. calyciflorus.