Study On The Roles Of Male Octodonta Nipae(Coleoptera:Chrysomelidae) Cuticular Hydrocarbons In Female Mating Choice

Insect cuticular hydrocarbons(CHCs)are usually regarded as kinds of contact sex pheromones,the components and contents of which are discrepant between different ages or different sexes.And they also have a significant effect on female mating choice.In this study,chemical components of CHCs of O.nipae were analyzed to clarify the differences between different ages and/or different sexes using chemical extraction method and gas chromatography-mass spectrometry(GC-MS)technology.Meanwhile,the effect of male CHCs in female mating choice was revealed through insect behavior experiments.The main results were as follows:1.The absolute content of CHCs between male and female was different,but there was no difference in components,which are called sex dimorphism.There were 21 kinds of CHCs in both male and female O.nipae,including 11 kinds of n-alkanes(n-C20—n-C30),3 kinds of n-alkenes(1-C20ene,(10E)-C2iene,1-C22ene),2 kinds of monomethylalkanes(2-Me-Ci9ane,10-Me-C20ane),1 kind of monomethylalkene(5-Me-(5Z)-C22ene),1 kind of polymethylalkane(2,6,10,15-Tetramethyl-C21 ane),3 kinds of cycloalkanes(cyclotetracosane,cyclooctacosane,cyclotriacontane).2.With eclosion days increasing,average absolute content of O.nipae CHCs had a decreased trend from 1 d to 10 d,but suddenly increased and others CHCs(except n-C27)was higher in male than female at 15 d(sexual maturation day).There were significant average absolute content differences of 2-Me-C19ane,n-C20ane,10-Me-C20ane;1-C20ene,n-C2iane,n-C26ane between male and female at sexual maturation.Among them,1-C20ene was the most significant and average absolute content of male was about 7 times as much as that of female.In addition,compared among different eclosion days,relative content of olefin and cycloalkanes produced by male were the highest at 15 d,but relative content of alkanes was the highest at 1 d;While relative content of olefin and cycloalkanes produced by female were highest at 1 d,relative content of alkanes was the least at 1 d.Therefore,we speculate that chemical signals are mainly transmitted by dynamic changes of the absolute content and relative content of specific cuticular hydrocarbons(such as n-alkanes,methyl alkanes,olefin and cycloalkanes).3.Multivariate nonlinear correlation analysis based on PLS-DA showed that 9 kinds of male CHCs had negative effects on female mating choice.The influence from high to low were as follows:n-C25,2,6,10,15-tetramethyl-C2iane,1-C22ene,2-Me-C19ane,5-Me-(5Z)-C22ene,n-C20,Cyclotetracosane,n-C24,and n-C19.In other side,12 kinds of male CHCs had positive effects on female mating choice,the influence from high to low were as follows:n-C30,cyclooctacosane,10-Me-C20ane,cyclotriacontane,(10E)-C2iene,n-C22,1-C20ene,n-C26,n-C23,n-C21,n-C28,and n-C27.4.Three dissimilarity indices analysis showed that female 0.nipae was based on male specific CHCs rather than CHCs absolute contents dissimilarity between mating pairs to choose mating success or not.In conclusion,CHCs,which is one of important semiochemicals,had a significant effect on intraspecific differentiation and female mating choice.Moreover,this research will provide a new idea and approach for the development of novel pest inhibitors and behavioral interference agents targeting the insect CHCs.