The changes in CAT activity are depicted in Fig. 1b. Compared to
the controls, the CAT activities in the 0.25 mg kg1 spirotetramat
treatment were induced significantly (p < 0.01) on days 7 and 14
only, by 37.3% and 39.1%, respectively. In the 1.25 and 2.5 mg kg1
treatments, the CAT activities were significantly greater (p < 0.05)
than the controls on day 2, by 28.6% and 27.9% respectively.
However, with the extension of exposure time, the activities of
CAT in 1.25 and 2.5 mg kg1 treatments were significantly lower
(p < 0.05) than the controls on day 14, 21, and 28. The dose, duration,
and the interaction of the dose and duration all play crucial
roles in determining the CAT activity in earthworms exposed to
spirotetramat (Table 1).