金龟甲对蓖麻叶挥发物的触角电位和行为反应

为了探明金龟甲偏爱选择有害非寄主植物蓖麻的原因,应用触角电位（EAG）仪和“Y”型嗅觉仪,分别测定了华北大黑鳃金龟、暗黑鳃金龟和铜绿丽金龟雌、雄虫对5种蓖麻叶挥发物的触角电位和选择行为反应。EAG测定结果表明,3种金龟甲雄虫对各处理挥发物的EAG反应值均比参照挥发物顺-3-己烯-1-醇强。华北大黑鳃金龟对邻苯二甲酸二丁酯和肉桂醛的EAG反应值相对较高,暗黑鳃金龟对苯甲醇的EAG反应值相对较高,铜绿丽金龟对邻苯二甲酸二丁酯和苯甲醇的EAG反应值相对较高。选择行为反应测定结果表明,当顺-3-己烯-1-醇与其他挥发物配对测试时,华北大黑鳃金龟对邻苯二甲酸二丁酯和肉桂醛2种蓖麻叶挥发物表现出明显的选择偏好,暗黑鳃金龟对蓖麻叶挥发物苯甲醇表现出明显的选择偏好,铜绿丽金龟则更偏好选择蓖麻的绿叶气味物质顺-3-己烯-1-醇。总之,蓖麻叶的挥发性物质与引诱金龟甲偏爱选择密切相关,且偏爱的挥发物因金龟甲的种类而异。

Electroantennographic and behavioural responses of scarab beetles to Ricinus communis leaf volatiles

Holotrichia oblita, H. parallela and Anomala corpulenta are important pests in the dry land areas of North China, which feed roots or stems of plants in larvae stage and leaves of variety of plants in adult stage. Most interestingly, three species all prefer to feeding on leaves of Ricinus communis, a non-host plant, despite that the extract of R. communis leaf is toxic to their larvae and adults. In order to elucidate the mechanisms behind this phenomenon, in the present study, the electroantennographic and behavioural responses of the male and female adults of three scarab beetle species to five components of R. communis leaf volatiles were tested using the electroantennogram (EAG) and a Y-typed olfactometer, respectively. The EAG bioassay showed that the relative EAG values of three species male scarab beetles were higher to four components, i.e., dibutyl phthalate, cinnamaldehyde, 2-phenylethanol and benzyl alcohol, than that to control volatile (Z)-3-hexene-1-ol, especially the males of H. oblita exhibited strong responses to dibutyl phthalate and 2-phenylethanol, with 200.34% and 168.43% relative EAG values, respectively. Corresponding females of H. oblita responded strongly to cinnamaldehyde and dibutyl phthalate with the 146.01% and 135.12% relative EAG values, respectively. The relative EAG values of H. parallela to benzyl alcohol arrived 149.95%(male) and 167.86%(female). A. corpulenta exhibited responses to dibutyl phthalate with about 144% the relative EAG values. The response of A. corpulenta male to benzyl alcohol is strong with the 143.70% relative EAG values. The results of behavioural bioassay indicated the preference to volatiles derived from R. communisis is species-dependent, that is, H. oblita exhibited significant preferences to dibutyl phthalate and cinnamaldehyde, with the choice response percentages of 64% and 63% in females and 76% and 65% in males, significantly higher than that to (Z)-3-hexene-1-ol. Females and males of H. parallela showed significant preference to benzyl alcohol, with the 66% and 56% mean choice response percentages, respectively. A. corpulenta was most preferred to a green leaf volatile (Z)-3-hexene-1-ol, and the average choice response percentages of males and females to (Z)-3-hexene-1-ol were 88%, 87% and 89% in the controls of dibutyl phthalate, cinnamaldehyde and 2-phenylethanol, respectively. The results of comparison between R. communis volatiles and the female-produced sex pheromones of the tested scarab beetle species, found that R. communis leaves emitted abundant dibutyl phthalate, while the major components of H. oblita female-produced sex pheromone were glycine methyl ester and proline methyl ester, and the major component of H. parallela female-produced sex pheromone was methyl L-isoleucinate. Therefore, "sex pheromone misleading" may possibly answer for the preferences of two Holotrichia species to R. communis. The green leaf volatile (Z)-3-hexene-1-ol may possibly be the main attractant of A. corpulenta to R. communis.