| Scleroderma guani Xiao et Wu(Hymenoptera: Bethylidae)is the ectoparasitoid of many Coleoptera and Lepidoptera insects.The parasitoids has the characteristics of high reproductive rate,strong parasitic ability and wide host range,so it is widely used in biological control of many forest insect pests.At present,some progress has been made in biological habit,artificial breeding and field release technology of S.guani.And its behavior research is mainly focused on host search,selection and utilization.Few studies have been made in its maternal care behavior.In this paper,the research object is S.guani and Monochamus alternatus.Our aim was to evaluate the characteristic of maternal care behavior of S.guani females,and its effects on offspring fitness;moreover,analysing and screening main chemical information from S.guani offspring in different developmental stages.This study will indicate the biological significances of S.guani's maternal behavior,and its relevant chemical communication.It will provide an important potential for promoting the behavioral ecology research of Bethylidae parastoids and the mass rearing techniques of S.guani.1.Observation of maternal care behavior of S.guani female adultsIn order to further explore the behavioral characteristics of maternal care behavior in S.guani female adults,the experiments were to observe the maternal care behavior performance conducted by indoor feeding and video camera,and analyzed the temporal and spatial changes of maternal care behavior in different developmental stages.The observation showed: The main behavior performance of maternal care included walking and sounding in the offspring,transporting larva,assisted eclosion and mating with male offspring.(2)The female adults' behavior of walking and sounding under their offspring occurred mainly during the larva and pupa cocoon stages.In egg stage,the time of walking and sounding under their offspring was less(1.448±0.984 min),which spent more time under the host and other area(409.245±19.478 min).After the eggs hatched to larva,the maternal time under the offspring increased,when in mature larva and spinning mature larva stage,the maternal time reached to more than 470 min,which was far high than that in host and other area(100.224±16.712 min and 108.808±26.268 min).(3)The transporting behavior is an important behavioral process in S.guani maternal care,which occured in mature larva,spinning mature larva and pupa cocoon stage,especially in the mature larvae stage.The occurrence frequency of this behavior was about 16.833±1.761/600 min,accounting for 17.027% of the total time,while the transporting time was less than 0.1% of the total time in spinning mature larva and pupa cocoon stage.(4)When offspring emergences,some mothers bite the cocoon and assist eclosion of offspring.The frequency of assist eclosion was 3.625±0.925/600 min,and the time of this behavior was 12.952±4.050 min.Besides,some mothers can mate with male offspring,but its frequency was less(0.333±0.167/600min).2.Effects of maternal care of S.guani on its offspring developmental performanceThe offspring developmental performance of S.guani was tested in different maternal care treatments(removing female adults in different developmental stages and the control(maternal care in the whole stages).The result showed that: In the experimental group lack of maternal care in egg stage,the mean developmental duration of early instar larva prolonged obviously,being 1.6-fold as high as that of the control group.However,when there was a lack of maternal care in different developmental stages,the mean developmental duration of mature larva only prolonged 0.885 d compared with the control group.Lack of maternal care in egg and larval stages did not facilitate the offspring survival.In the experimental groups without maternal care in egg stage,the survival rates of mature larva and spinning mature larva were 22.080±5.862% and 17.430±4.550%,respectively,which were only 1/3 and 1/4 of the control group.In the experimental groups lack of maternal care in egg stage,early-instar larva,late-instar larva and mature larva,the offspring infection rates by Beauveria bassiana were all above 40%,especially in the experimental group lack of maternal care in early instar larva,the infection rate was up to 65.680±3.503%,which was 11-fold as high as that of the control.The results of this study suggested that the maternal care of S.guani can promote the development and survival rate of offspring and reduce the infection rate of offspring by pathogen,which has important significance to the parasitoid's population reproduction.3.Chemical information substances that affect the maternal care behavior of S.guani female adultsAccording to qualitative and quantitative analysis the chemical information substances in the different development stages of S.guani offspring by GC-MS,the result showed that: A total of 31 compounds were identified from the extracts of mother and offspring,including n-alkanes,alcohols,fatty acids,esters and terpenes.Among them,1-Hexadecanol was founded in the eggs and early-instar larva,which content were 0.182±0.002 ng/per wasp and 0.627±0.003 ng/per wasp,while cis-Vaccenic acid was existed in the surface of mature larva,spinning mature larva and pupa cocoon(0.139±0.079 ng/per wasp,0.354±0.093ng/per wasp,2.539±0.058 ng/per wasp).Hexadecanoic acid ethyl ester only existed in mature larva(2.640±0.020 ng/per wasp)and the n-Hexadecanoic acid was a special substance on the surface of pupa cocoon(20.626±1.732ng/per wasp).The content of alkanes and alkenes on the surface of the female adult was higher than that of other stages.The n-Tetracosanol-1 and 1-Heptacosanol on the surface of cocoon pupa were respectively 644.688±120.981 ng/per wasp)and 3414.783 ±508.146 ng/per wasp),which was higher than that of others.The behavior responses of the female to the offspring,the crude extracts and the standard compounds were determined by the selective test.Result indicated that:(1)The successful selection rate of the crude extracts in mature larva and pupa cocoon was higher(23.000±4.812% and 35.500±6.304%),as the same as the residence time(33.196±3.884 min and 45.169±9.567min).In addition,Tricosane,Heptacosane,n-Hexadecanoic acid and Hexadecanoic acid ethyl ester can cause the female to selection behavior.The characteristics of the transporting behavior and the effect on the offspring's movement and survival were verified by non selective test.The research showed: Under the condition of no female,the mature larvae were able to leave the host,and distributed in the discrete state around the host,but the rate of detachment was lower,only about 37%;however,when transported by female,the mature larvae were separated from the host,which the accumulation rate was up to 75%,and the survival rate was up to 83%,being 2.115-fold as high as that of no female.According to the analysis and identification of the main chemical substances in the surface of the mature larvae,12 kinds of main materials were selected as the standard to simulate the mature larvae to verify whether these substances could cause the transporting behavior of female.The study showed that Hexadecanoic acid ethyl ester,(Z)-9-Tricosene and 1-Heptacosanol can induce the transporting behavior of females. |
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