镉对大型溞摄食能力和相关生理指标的影响

为了探究镉处理对大型溞(Daphnia magna)摄食能力的影响及其机制, 实验设置了3个镉浓度组(0.01、0.05和0.09 mg/L)、1个空白对照和2个处理时间(24h、48h), 研究镉处理对大型溞摄食率与滤水率、体内镉的蓄积量、总抗氧化能力(T-AOC)和脂质过氧化水平(MDA含量)以及乙酰胆碱酯酶(AChE)活性的影响。结果显示, 摄食率和滤水率均随着镉处理浓度的增加而逐渐降低, 当镉浓度为0.09 mg/L, 处理48h时, 摄食率和滤水率均显著或极显著低于对照组(P<0.05,P<0.01), 且摄食率与对照组相比降低了43.89%; 镉在大型溞体内的积累量随镉处理浓度的增加而逐渐升高; T-AOC和MDA含量随着镉浓度的增加而增高, 镉浓度0.09 mg/L时, T-AOC和MDA含量与对照组相比有显著性差异(P<0.05), 且T-AOC与摄食率之间呈负相关性, 相关系数R2分别为0.9521、0.9389; AChE活性随着镉浓度的增加而降低, 镉浓度为0.05、0.09 mg/L时AChE活性显著低于对照组(P<0.05)。这表明镉在体内的蓄积不仅造成了大型溞的氧化损伤, 而且引起了神经系统传导功能的异常, 导致了大型溞摄食能力受到抑制。

EFFECT OF CADMIUM ON THE FEEDING CAPACITY AND PHYSIOLOGICAL STATUS OF DAPHNIA MAGNA

To investigate the effects of cadmium (Cd2+) on the feeding capacity and its mechanism of water flea, Daphnia magna, three experimental groups with different Cd2+ concentrations (0.01 mg/L, 0.05 mg/L and 0.09 mg/L) and one control group were set up in this study, and these groups were exposed for 24h and 48h, respectively. The effects of Cd2+ levels on the feeding and filtration rate, tissues accumulation of Cd2+, total antioxidant capacity (T-AOC), contents of malonyldialdehyde (MDA), and the activities of acetylcholine esterase (AChE) in D. magna were analyzed. The results showed that (1) the feeding and filtration rates of D. magna decreased with increasing Cd2+ concentrations. Especially, when the D. magna was exposed to 0.09 mg/L Cd2+ for 48h, the feeding and filtration rates dropped dramatically (P<0.05,P<0.01), with the feeding rate decreasing by 43.89% compared to the control group. (2) With the increase of Cd2+ concentration, the accumulation of Cd in tissues was significantly higher in the experimental groups than that in the control group. (3) The total antioxidant capacity (T-AOC) and content of MDA in the water flea increased gradually with the concentration level of Cd2+. In the group with Cd2+ concentration of 0.09 mg/L, the levels of T-AOC and MDA increased significantly (P<0.05) compared to the control group. T-AOC was negatively correlated with the feeding rate whose correlation coefficientR2 were 0.9521 and 0.9389, respectively. (4) The activity of AChE decreased with increasing Cd2+ concentration, especially when D. magna were exposed to higher concentrations of 0.05 and 0.09 mg/L (P<0.05). The results indicated that Cd2+ stress not only caused oxidative damage to water flea, but also induced the abnormal conduction function to the nerve system, which would result in inhibition of feeding behavior in D. magna.