食物密度对镜湖萼花臂尾轮虫不同克隆生活史特征的影响

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

对镜湖萼花臂尾轮虫(Brachionus calyciflorus)夏季种群内4个生化遗传特征上互不相同的克隆(克隆A、B、C和D)在4个斜生栅藻(Scenedesmus obliquus)密度(1.0×106、2.0×106、4.0×106和8.0×106 cells·L-1)下的生活史特征进行了研究.结果表明:食物密度对各克隆轮虫的存活率和繁殖率均有不同的影响.4克隆中克隆C的世代时间最短,克隆B的世代时间、生命期望和平均寿命最长,克隆A的后代混交雌体百分率最高;净生殖率和个体适合度在4克隆间无显著差异.镜湖萼花臂尾轮虫在2.0×106 cells·L-1的食物密度下净生殖率最低;在1.0×106 cells·L-1的食物密度下平均寿命和生命期望最短,而后代混交雌体百分率却最高;在8.0×106 cells·L-1的食物密度下种群内禀增长率最高,平均寿命和生命期望最长;在高食物密度(4.0、8.0×106 cells·L-1)下个体适合度较大.克隆C的个体适合度在密度为3.9×106 cells·L-1时最小,而克隆D的个体适合度在食物密度为6.34×106 cells·L-1时最大.食物密度的变化可能是7月份之后镜湖萼花臂尾轮虫从水环境中消失的原因,而4克隆轮虫个体适合度的相似性则可能是镜湖轮虫共存于同一水体的原因之一.

Four Braehionus calyciflorus 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 ℃ under the conditions of feeding with 1.0 ×10^6, 2. 0 ×10^6, 4. 0 ×10^6 and 8.0 × 10^6 cells · L^-1 of Scenedesmus obliquus. The results showed that S. obliquus concentration had different effects on the survival rate and fecundity of different B. calyeiflorus 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 ×10^6 cells ·L^-1 ofS. obliquus, the net reproductive rate ofB. ealyeiflorus was the lowest; at 1.0 ×10^6 ceils ·L^-1 ofS. obliquus, B. calyciflorus had the shortest average lifespan and life expectancy but the highest mictic rate in its offspring; at 8.0 ×10^6 cells ·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 ×10^6 cells ·L^-1 of S. obliquus, the individual fitness of B. calyciflorus was the highest. Clone C had the smallest individual fitness at 3. 9 ×10^6 cells ·L^-1 of S. obliquus and clone D had the highest one at 6.34 ×10^6 cells ·L^-1of 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 Jinghn 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.