[Effects of food concentration on life history traits of Brachionus calyciflorus clones in Jinghu Lake].

Four Brachionus calyceflorus clones (clone A, B, C, and D) different in biochemical and genetic characteristics were collected from Jinghu Lake in summer, and their life history traits were studied at 25 degrees C under the conditions of feeding with 1.0 x 10(6), 2.0 x 10(6), 4.0 x 10(6) and 8.0 x 10(6) cells x L(-1) of Scenedesmus obliquus. The results showed that S. obliquus concentration had different effects on the survival rate and fecundity of different B. calyciflorus clones. Among the four clones, clone C had the shortest generation time, clone B had the longest generation time, life expectancy and average lifespan, and clone A had the highest percentage of mictic females in its offspring. No significant differences were observed in the net reproductive rate and individual fitness among the four clones. At 2.0 x 10(6) cells x L(-1) of S. obliquus, the net reproductive rate of B. calyceiflorus was the lowest; at 1.0 x 10(6) cells x L(-1) of S. obliquus, B. calyciflorus had the shortest average lifespan and life expectancy but the highest mictic rate in its offspring; at 8.0 x 10(6) cells x L(-1) of S. obliquus, B. calyciflorus had the highest intrinsic rate of population increase and the longest average lifespan and life expectancy; and at 4.0 and 8.0 x 10(6) cells x L(-1) of S. obliquus, the individual fitness of B. calyciflorus was the highest. Clone C had the smallest individual fitness at 3.9 x 10(6) cells x L(-1) of S. obliquus and clone D had the highest one at 6. 34 x 10(6) cells x L(-1) of S. obliquus, while the individual fitness of clones A and B was not correlated with S. obliquus concentration. After July, the disappearance of genetically different B. calyciflorus clones from Jinghu Lake might attribute to the variation of algal food concentration, and the similar individual fitness of the four clones might be one of the reasons that contribute to the coexistence of B. calyciflorus clones in Jinghu Lake in summer.