The Responses Study Of Drosicha Corpulenta (Kuwana) To Their Host Volatiles

Drosicha corpulenta (Kuwana) (Insecta:Hemiptera:Coccoidea: Monophlebidae) is the herbivorous insect of forest and fruit trees with wide distribution in China. The research which was based on the behavioral manipulation provided the theoretical basis to the bio-control of D. corpulenta with the study of ultrastructure and possible fuction of antennal sensilla. The research consists of the following three parts:(1) The behavioral responses of D. corpulenta toward the odors released from the different plants by using the "Y-shape" olfactometer and honeydew chromogenic method; (2) The type, morphology, number and distribution of antennal sensilla of D.corpulenta by using light microscope, scanning and transmission electron microscope; (3) The amino acid sequence analysis of antennal odorant-binding proteins (OBPs) of the female adults.The results as follows:1.The study measured the behavioral responses of the the 2nd-instar nymphs and female adults of D. corpulenta toward the odors released from the twelve species of host plants and six species of the non-host plants, and evaluated the effect on the honeydew excretion of the D. corpulenta against the four non-host plants extracts by using the honeydew chromogenic method. The results showed that both the nymphs and female adults displayed obviously taxis responses to the volatile of host plants Diospyros kaki, Ziziphus jujuba and Populus tomentosa. The inducing effect of D. kaki reached the extremely significant difference level and the inducing rate for the nymphs and adults were 68.9% and 74.7%, respectively. However, the volatile and alcoholic extracts of the non-host plants, Zanthoxylum bungeanum, Ailanthus altissma, Mentha haplocalyx and Forsythia suspense displayed remarkable repellency effect on the scale insect. In comparison, the volatile of Amygdalus triloba only exhibited the remarkable repellent effect on the female adults. The alcoholic extracts of Z. bungeanum and A. altissma showed the strongest effect on the nymphs with excretion decrement rate 70.6% and 70.1% and the female adults with 80.5% and 72.4%, respectively. As above mentioned, D. kaki possessed of the strongest inducing effect, while Z. bungeanum and A. altissma (Mill.) had the strongest repellency effect on the nymphs and female adults.2.The antennal morphology, and number, distribution and ultrastructural character of antennal sensilla of the 2nd-instar nymphs and male and female adults of D.corpulenta were as followed:The short and brown antenna of the 2nd-instar nymphs and female adults were clavate with three segments, which consisted of the scape, pedicel and flagellum. Differently, the antenna of the 2nd-instar nymphs had four subsegments of flagellum and six on female adults. We found nine types of sensilla, including two types of sensilla trichodea (ST), two types of sensilla basiconica (SB), sensilla chaetica (SCh), sensilla coeloconica (SCo), sensilla campaniformia (SCa) and two types of sensilla peg (SP). The antenna of the male adult of D. corpulenta was filiform with the scape, pedicel and eight subsegments of flagellum. The bead-like antenna with the insertion of many hairs was long and black. We found eleven types of sensilla, including three types of ST, two types of SB, two types of SCh, SCa, SCo, SP and peripheral scolopidia (PS).Every type of antennal sensilla varied significantly in morphology, number and distribution with each other. The length of ST, SCh and SP gradually increased with the change of stages and the rest had no change. Mostly were on the antennal dorsum, venter and the outboard:ST accounted for 80% with the high density on the whole antenna; SCa was only one and inserted on the venter of pedicel; the 2nd-instar nymphs and female adults had two types of SP that one was present on the last segment which was same with the male adults, and another mainly clustered on the venter of the 1st and 2nd subsegment of flagellum; The types of SB of adults were one more than the 2nd-instar nymphs and female adults; Two types of SCh of male adults had the different distribution that one present on the last segment and another was on the scape and pedicel as same as the 2nd-instar nymphs and female adults; SCo maily clustered on the pedicel and the last subsegment of flagellum; PS only clustered on the pedicel.The ultrastructural results showed that all the SB with thin wall, many pores and large number of dendritic branches in sensillar lymph and the STⅠ on the antenna of male adults with thick wall, pores and two dendritic branches possibly functionated olfactory; The STⅡ of male adults possibly functionated olfactory and mechanical with thick wall, less pores and tubular body in sensillar lymph; the STⅠ of the 2nd nymphs and female adults and the STⅢ and SChⅡ of male adults with thick wall, no pores and no dendritic branches, all PS, and SCa were typical mechanoreccptor; the SCh present on the antenna of female adults and the SChⅠ of male adults possibly functionated chemical and mechanical with thick wall, some pores and dendritic branches in inner sensillar lymph. SP with thin wall, many pores and dendritic branches and a lateral pore, and SCo with a terminal pore possibly functionated gustatory.3.Antennal RNA of female adults was extracted and the cDNA was gained. Meanwhile, the RNA-seq analysis of the antennal transcriptome was studied. Altogether 17 putative OBPs amino acid sequence of D. corpulenta was gained and they all had six conservative cysteine, which had the characteristic insect OBPs sequence motif "C1-X15-39-C2-X3-C3-X21-44-C4-X7-12-C5-X8-C6". Among the 17 putative DcOBPs,14 belonged to the confirmed OBPs by using blastp. Compared with the insects of Aphididae aphids, in the same suborder with D. corpulenta, the identities of OBPs were only 28%-35%. And DcOBP-3 had the higher identity with OBP4 of Adelphocoris lineolatus, reaching 46%.