甘蓝饲养小菜粉蝶幼虫对两种寄主植物叶片汁液的行为及电生理反应

目的]探讨小菜粉蝶幼虫对2种寄主植物(甘蓝和旱金莲)叶片汁液的行为及电生理反应,为阐明植食性昆虫寄主植物选择机制提供一定的理论依据.方法]小菜粉蝶幼虫孵化后饲养在甘蓝叶片上,选用进入5龄24~48 h的小菜粉蝶幼虫供试;植物叶片榨出汁液,用行为试验双选法测试幼虫对汁液的行为反应,用顶端记录法测试幼虫侧栓锥和中栓锥味觉感受器对汁液的电生理反应.结果]行为试验结果表明,甘蓝饲养小菜粉蝶幼虫取食含有甘蓝叶片汁液的玻璃纤维滤纸圆片极显著多于取食含有旱金莲叶片汁液的圆片(P<0.001).电生理试验表明,侧栓锥味觉感受器对2种叶片汁液的电生理反应均显著强于中栓锥味觉感受器(P<0.01),且侧栓锥味觉感受器对旱金莲叶片汁液的电生理反应显著强于甘蓝叶片汁液(P<0.01),而中栓锥味觉感受器的反应对两者无显著差异(P>0.05);侧栓锥味觉感受器有3个味觉神经元对叶片汁液有反应,中栓锥味觉感受器只有2个味觉神经元对叶片汁液有反应,且侧栓锥味觉感受器中味觉神经元1和神经元2对旱金莲叶片汁液的反应频率极显著强于对甘蓝叶片汁液的反应频率(分别为P<0.01和P<0.001),味觉神经元3对两者反应无显著差异(P>0.05);中栓锥味觉感受器中味觉神经元1和神经元2对旱金莲叶片汁液和对甘蓝叶片汁液的反应频率则无显著差异(P>0.05).结论]甘蓝饲养小菜粉蝶幼虫对旱金莲叶片汁液有拒食行为,这种拒食行为与侧栓锥味觉感受器中相关味觉神经元的激活有关.小菜粉蝶幼虫侧栓锥味觉感受器对2种寄主植物叶片的反应均显著强于中栓锥味觉感受器,说明在对寄主植物的探测上侧栓锥味觉感受器可能起到更重要的作用.

Behavioral and electrophysiological responses of Pieris rapae larvae cultured on Brassica oleracea L. to leaf saps of two host plants

Objective]Behavioral and electrophysiological responses of Pieris rapae larvae to two natural host plants (Brassica oleracea L. var. gemmifera cv. Cyrus L. and Tropaeolum majus L. cv. Glorious Gleam) saps in order to pro-vide reference for host selection mechanism of phytophagous insects. Method]After P. rapae larvae were hatched, they were cultured on B. oleracea L. leaves, then the larvae growing into 5th instar for 24-28 h were used for the experiment. The leaves were squeezed to obtain the sap, and double-choice behavior experiment was used to test behavioral responses of the larvae to saps, top recording method was applied to test electrophysiological responses of larvae lateral styloconic sensillum(L-sensillum) and medial styloconic sensillum(M-sensillum) to saps. Result]Behavior experiment results in-dicated that, glass fiber filter paper disc in larvae feeding B. oleracea L. sap was extremely significantly more than those feeding T. majus L. sap (P<0.001). Electrophysiological experiment indicated that electrophysiological responses of L-sensillum to the two saps were significantly stronger than M-sensillum(P<0.01). Moreover, electrophysiological respons-es of L-sensillum to T. majus L. sap was significantly stronger than B. oleracea L. sap(P<0.01). There was no obvious di-fference in electrophysiological responses of M-sensillum to the two saps(P>0.05). Three gustatory neurons in L-sensillum responded to saps, but only two gustatory neurons in M-sensillum responded to saps. Meanwhile, in L-sensillum, response frequencies of gustatory neuron 1 and gustatory neuron 2 to B. oleracea L. sap were extremely significantly stronger than T. majus L. sap(P<0.01 and P<0.001 respectively), the response of gustatory neuron 3 to the two saps showed insignificant difference(P>0.05). In M-sensillum, response frequencies of gustatory neuron 1 and gustatory neuron 2 to B. oleracea L. sap and T. majus L. sap presented insignificant difference(P>0.05). Conclusion]P. rapae larvae fed by B. oleracea L. present rejection to T. majus L. sap, and such rejection is related to activation of gustatory neurons in L-sensillum. The re-sponse of the larvae L-sensillum to the two plant leaves are significantly stronger than M-sensillum, which indiates that L-sensillum plays a more important role in detecting host plant.