汀棠湖冬季出现的萼花臂尾轮虫对水温的适应

Adaptation of Brachionus calyciflorus(Rotifera) occurred in winter in Lake Tingtang to water temperature: a life table demography study

为了解汀棠湖冬季出现的萼花臂尾轮虫对水温的适应,探讨其在春季的种群消长机制,运用生命表统计学方法研究了温度(12℃、16℃、20℃和24℃)和斜生栅藻(Scenedesmus obliquus)密度(1.0×106、3.0×106和5.0×106个/mL)对冬季采自芜湖市汀棠湖水体中的萼花臂尾轮虫(Brachionus calyciflorus)出生时的生命期望、世代时间、平均寿命、总生殖率、净生殖率和种群内禀增长率等生活史参数的影响。结果表明,温度对轮虫出生时的生命期望、世代时间、平均寿命、净生殖率和种群内禀增长率均有显著性影响(P<0.05),但对总生殖率无显著性影响(P>0.05);食物密度以及食物密度与温度之间的交互作用对轮虫所有生命表统计学参数均无显著性影响(P>0.05)。轮虫出生时的生命期望和平均寿命在12℃下较长,16、20℃和24℃下较短且三者间无显著性差异;轮虫的世代时间在12℃下最长,16℃和24℃下最短且两者间无显著性差异;轮虫的净生殖率在16℃下较高,12、20℃和24℃下较低且三者间无显著性差异;轮虫的种群内禀增长率在12℃下最低,16℃下最高,20℃和24℃间无显著性差异。汀棠湖冬季出现的萼花臂尾轮虫在16℃下的适合度最高,这或许是该水体中萼花臂尾轮虫种群密度在3月中旬(此时水温为17℃)达到春季最高峰的重要原因之一。

In order to investigate the adaptation of Brachionus calyciflorus occurred in winter in Lake Tingtang to water temperature, we studied the effects of temperature （12℃, 16℃, 20℃ and 24℃ ） and Scenedesmus obliquus density （1.0×10^6, 3.0×10^6 and 5.0×10^6 cells/mL） on life table demographic parameters including life expectancy at hatching, generation time, average lifespan, gross reproductive rate, net reproductive rate and intrinsic rate of population increase of B. calyciflorus. The results showed that at 1.0×10^6 cells/mL of Scenedesmus, the life expectancy at hatching, the generation time and the average lifespan of the rotifers at 12℃ were all longer than those at 16℃ , 20℃ and 24℃, and the rise of food level did not changed their reaction norms to increasing temperature, except that at 5.0×10^6 cells/mL of Scenedesmus, the generation time of the rotifers at 20℃ was longer than that at 16℃. At 1.0×10^6 cells/mL of Scenedesmus, the gross reproductive rate of the rotifers at 16℃ was higher than that at 24℃, but both of them were similar to those at 12℃and 20℃. At 3.0×10^6 and 5.0×10^6 cells/mL of Scenedesmus, the gross reproductive rate of the rotifers was similar among the four temperatures （P〉0.05）. At 1.0x 106 and 5.0×10^6 cells/mL of Scenedesmus, the net reproductive rate of the rotifers at 16℃ was higher than that at 12℃, 20℃ and 24℃ ; the intrinsic rate of population increase at 16℃ was the highest, but that at 12℃the lowest. At 3.0×10^6 cells/mL of Scenedesmus, the gross reproductive rate of the rotifers was similar among the four temperatures （P〉0.05） ; the intrinsic rate of population increase at 16℃ and 24℃ was the highest, but that at 12℃ the lowest. At each of the temperatures, food level did not affect all the life table demographic parameters （P〉0.05）, except that at 24℃ food level affected significantly the net reproductive rate and the intrinsic rate of population increase （P〈0.05）. Two-way ANOVA showed that temperature affected significantly nearly all the life table demographic parameters （P〈0.05）, except the gross reproductive rate （P〉0.05）. However, food level, and the interaction between food level and temperature did not affect all the life table demographic parameters （P〉0.05）. Both the life expectancy at hatching and the average lifespan were longer at 12℃ than those at 16℃ , 20℃ and 24℃. The generation time was the longest at 12℃ , but the shortest at both 16℃ and 24℃. The net reproductive rate was higher at 16℃ than that at 12℃, 20℃ and 25℃. The intrinsic rate of population increase was the lowest at 12℃ , the highest at 16℃ , and similar at 20℃ and 24℃. B. calyciflorus occurred in winter in Lake Tingtang has the highest fitness at 16℃, which might be one of the important reasons for its maximal population density occurring at mid-March when the water temperature is 17℃.