Abstract: The piezoelectric bulk acoustic wave (BAW) impedance analysis method was employed to monitor in situ the proteinase-catalyzed hydrolyzation of casein and the effect of methamidophos pesticide on the midgut proteinase activity of the wolf spider, Pardosa pseudoannulata, and its results were verified by ultraviolet spectroscopy. The results showed that hydrolyzation was significantly increased in the presence of low-dose methamidophos, whereas the hydrolyzation was significantly inhibited in the presence of high-dose methamidophos, and a correlation was found precisely between the enzyme activity reflected by the final frequency shift after the hydrolyzation and the concentration of methamidophos. The present work may have presented a novel method feasible for studying the mechanism of excitability of spiders under low-dose methamidophos pesticide and quick detection of proteinase activity.  

Key words: Pardosa pseudoannulata,  methamidophos； midgut proteinase； enzyme activity； ultraviolet spectroscopy； piezoelectric bulk acoustic wave impedance method