LIFE HISTORY TRAITS OF DIFFERENT CLONES FROM SUMMER POPULATION OF BRACHIONUS CALYCIFLORUS (ROTIFERA)IN LAKE JINGHU

By means of life table demographic approach, four biochemical-genetically different Brachionus calyciflorus clones (Clone A, B, C and D)collected from Lake Jinghu in summer were cultured at 15℃, 20℃, 25℃ and 30℃ with 3.0 ×106 cells/mL of Scenedesmus obliquus to investigate their differences in life history characteristics and their responses to increasing temperature.The results showed that the effects of temperature on the survivorship and the fecundity of B.calyciflorus differed with rotifer clones.At the same temperature, and among the four rotifer clones, there were significant differences in the life table parameters including generation time, average lifespan, life expectancy at hatching, net reproductive rate and intrinsic rate of population increase except the generation time and the net reproductive rate at 20℃ and 25℃ aswell as the average lifespan and the life expectancy at hatching at 20℃, 25℃ and 30℃.At 20℃, 25℃ and 30℃, the percentage of mictic females in the offspring of the four rotifer clones was significantly different, and that of Clone C was the highest.At 15℃, the individual fitness of Clone D was the highest;at 25℃, the individual fitness of Clone A and B was both higher among the four rotifer clones. There were some differences in responses of life history characteristics to increasing temperature among the four rotifer clones. Regardless of the temperature effect, and among the four rotifer clones, the average lifespan, generation time, life expectancy at hatching, net reproductive rate, intrinsic rate of population increase and individual fitness of Clone D were all the shortest and lowest, and the percentage of mictic females in the offspring of Clone C was the highest.At 30℃, the differences in the intrinsic rate of population increase of the four clones might cause different proportion of clone groups with different genotypes in the summer population, and the similar individual fitness of the four clones might be one of the main reasons that contribute to the coexistence of genetically different B.calyciflorus clones in Lake Jinghu in summer.