标准化测试中不同食物浓度对大型溞生长和繁殖的影响

Effect of food concentration on the growth and reproduction of Daphnia magna in a standard test

在标准化的大型溞繁殖试验中探讨食物浓度的合适表征指标和研究不同食物浓度对大型溞生长和繁殖的影响。结果表明:分别采用细胞计数法、光密度法和总有机碳分析法测定的斜生栅藻液细胞数量、吸光度和总有机碳浓度三者两两之间的线性方程相关系数r均大于0.917(P<0.01),线性相关性显著,三个指标有明显的可比性。从操作的角度考虑,光密度法最为简便,然而为体现不同种类食物提供的能量水平差异,以总有机碳浓度表征食物的浓度最为合适。幼溞的数量是反映亲溞繁殖能力的主要指标,设置的0.01、0.05、0.10、0.15、0.20和0.30 mg C·(溞·d)^(–1)食物浓度组所产幼溞数量的平均值和标准差分别为3±3、68±10、118±16、164±15、205±22和231±20,表明随着食物浓度的增加,亲溞繁殖幼溞的数量也相应增加,且在不同食物浓度组之间均存在显著性的差异(P<0.05)。当喂食浓度达到0.05 mg C·(溞·d)–1时,亲溞繁殖幼溞数量的平均值即能达到60只(大型溞繁殖试验的质量控制要求之一),因此,对于易吸附于藻细胞或被藻细胞降解的化学物质,大型溞繁殖试验中可调整食物浓度为0.05—0.1 mg C·(溞·d)^(–1),有利于受试物暴露浓度的维持。

Characteristic index for food （alga） concentration and the reproduction of Daphnia magna under different food concentrations in a standardization test were analyzed. The results indicated that all of the correlation coefficients r with paired comparison test within cell number, optical density and TOC of algal suspension were 〉 0.917 （P 〈 0.01）, and the three indexes were significantly comparable based on the linear relationship. Optical density method is more efficient in testing than the two other methods, while TOC determination is the best characteristic index for describing the difference in energy level supplied by different food. The number of offspring is an important parameter for the reproductive performance of parent. Number of offspring （mean ± SD） in the groups of 0.01, 0.05, 0.10, 0.15, 0.20 and 0.30 mg C·（Daphnia·d）-1 were 3±2, 68±10, 118±16, 164±15, 205±22 and 231±20, respectively. Their offsprings increased significantly （P 〈 0.05） with increasing food concentration among different groups. When the food concentration reached to 0.05 mg C·（Daphnia·d）-1, the mean of offspring number was above 60 （one of the test validity requirements in Daphnia magna reproduction test）. Therefore, if the Daphnia magna reproduction test is performed on the chemical substances to be absorbed or biodegraded by the alga cell, the food concentration can be decreased to the range from 0.05 to 0.1 mg C·（Daphnia·d）-1, which is good to maintain the exposure concentration stable during the test processes.