Study On The Molluscicidal Synergistic Effect Of Pedunsaponin A On Niclosamide

Pomacea canaliculata is known as an invasive malignant class.O ver the years,it has a significant impact on national agriculture production and human health in C hina.There are few types of molluscicides in the market,and the niclosamide is the main controling measure.Climbing up and escaping from water of the snail after contacting with niclosamide has led to the pestcides can’t be an ideal control effect.Subsequently,applying synergistic agents is approved to be the most effective way to improve current circumstances,a nd it is also suggested as an indispensable method to reduce the application amount and improve the effect of pesticides.We have found that pedunsaponin,which is one of the pueraria peduncularis,has a momentously toxic effect on Pomacea canaliculata,which can inhibit the climb-up of snails.In this study,we systemically researched the synergistic effect of Pedunsaponin A under zero effect concentration to niclosamide,and also furtherly explored the synergistic mechanism.The researching results are suggested as below:（1）Immersion method was applied on researching the synergism of Pedunsaponin A to niclosamide.By adding three concentration of Pedunsaponin A（0.2、0.4、0.8 mg/L）to niclosamide solution（0.6 mg/L）.The median lethal concentration(LC₅₀)value of the niclosamide added to Pedunsaponin A solution at 72h was lower than niclosamide（0.98 mg/L）and they were 0.66 mg/L,0.58 mg/L and 0.49 mg/L respectively,which exhibits the synergistic effect and the synergistic ratio was 1.33、1.53 and 1.82 respectively.An additional research on the inhibition of climbing and toxicity effect of 0.8 mg/L Pedunsaponin A to0.6 mg/L niclosamide,the climbing results showed that Pedunsaponin A could significantly inhibit the climbing of the snail,at 11h the snail climbing rate of niclosamide added to pedunsaponin A and niclosamide treated group were 0.00%（no snail climb-up）,33.3%.Results of field simulation poisoning experiment showed that at 72h the snail mortality of niclosamide added to pedunsaponin A and niclosamide treated group were 65.31%,37.39%,which indicates that 0.8 mg/L of Pedunsaponin A added to niclosamide could significantly increase the killing effect,and this synergistic effect may be associated with the in hibition climbing of the snail.（2）In the intention to study the effect of Pedunsaponin A to respiratory metabolism of the snail,we estimated the oxygen consumption and ammonia removal rate.The result suggested that the additional Pedunsaponin A to niclosamide solution could expressively decrease the respiratory metabolism.0.2、0.4、0.8 mg/L of Pedunsaponin A was respectively added to 0.6mg/L of niclosamide,at 24h the oxygen consumption rate was 0.21,0.056,0.053 mg/（g.h）and ammonia removal rate of the snail was 0.039,0.038,0.093mg/（g.h）respectively,above these two results were lower than the niclosamide treated group,and the oxygen consumption and ammonia removal rate were 0.24mg/（g.h）and 0.25mg/（g.h）individually.（3）The paraffin section method was adapted to study the histopathological effect of Pedunsaponin A and niclosamide mixed solution to the snail.The results showed that the niclosamide added to pedunsaponin A increased the destructive effect to liver,respiratory siphon,ventricular,kidney and pricardial coe lom,which caused the disappearance of the connective tissue in liver and wrinkle in lumen,cavity was observed in respiratory siphon,ventricular myofibers were exhibited free statues,the arrangement of parenchyma pricardial coelom cel s and kidney tubules were distorted.（4）The trypan blue staining and blood smear method were adapted to study the effect of niclosamide added to pedunsaponin A solution to the snail’s hemolymph.The results suggested that the additional Pedunsaponin A to niclosamide increased the effect to damage hemolymph,at 48h the hemolymph survival rate and proportion of basophil number were decreased and lower that the niclosamide treated group（77.3%and 31%）,correspondingly are 70.2%,0.96%.The proportion of eosinophils was higher than niclosamide treated group（1.86%）up to 3.35%.At 60h,the basophil cytoplasm was enlarged and then contracted,while the cytoplasm treated with niclonidramine was no obvious change.At 72h,the amount of hemocyanin of the snail in niclosamide added to pedunsaponin A treated group was declined84%compared with niclosamide treated group.