| Octodonta nipae Maulik is one of the most important quarantine pests in the south of China.For insects,pathogens and parasites around the host are the major restriction factors of insect expansion.Because their immune system against new pathogens around and constant reproduction enable them to break the bottleneck while lacking of native natural enemy in new surroundings,invasive insects could establish their populations and burst into a disaster in a new territory rapidly.Activation and response of insect immune system are the physiological basis to defense pathogenic and parasitic infestation.Reproduction is the important means of the expansion of population,and moreover,a major characteristic of insect life history.However,either the activation of insect immune system or the increase of insect reproduction is an expensive behavior.In addition,the storage and distribution of the material and energy are different between genders.Therefore,we hypothesized activation and response of immune system in O.nipae may lead to a cost of fecundity in material and energy,and the immune cost may be different between genders.The aim of our study is to clarify the dynamic changes of the immune response in O.nipae adults induced by bacteria and determine if the different response patterns exist between males and females,and explore the reproductive behavior adjustment between genders like mating and oviposition after immune induction.The results were shown as follows:1.The PO activity and the antibacterial activity of AMPs in O.nipae adults were significantly induced by the abdomen injection of LPS(2.5 mg/mL×138 nL)in a certain period,and the response models were different between females and males.The PO activities in the LPS-induced female(4-10 h post induction)and male adults(0-10 h post induction),as well as the antibacterial activity in the LPS-induced female(12-48 h post induction)and male adults(4-48 h post induction),were significantly higher than those of the blank control,respectively.After the injection of LPS,the PO activity was much faster increased than the antibacterial activity,but the increase of antibacterial activity lasted for a longer time.Before immune induction,the PO activity and the antibacterial activity of AMPs in female adults were significant higher than those in male adults;and after immune induction the PO activity and the antibacterial activity of AMPs in female adults also had a higher top level.2.Both LPS-injected females and males had different influences on the reproductive behavior of O.nipae.Compared with the controls,the injection of LPS showed no obvious effect on the mating rate of females while reduced significantly in the males.When the female and male were injected simaltaneously,the mating rate decreased more than that in the pair of LPS-induced males and females without injection.Similarly,the delay of starting the first copulation was more obviously in LPS-induced males than LPS-induced females.The mounting time during mating increased significantly in the male or female induced groups.However,the copulation time decreased in induced males and for induced females,it initially increase and then decrease.3.The copulation time paired with normal mate was only extended in 24 hours after LPS induction in females while remained unchanged in the LPS-injected males.The subsequent fecundity of ootheca-eggs decreased significantly.Interestingly,there are ootheca-free-eggs only in the groups of LPS-induced female mated with blank control male.The results above indicated that LPS could induced the up-regulation of the immunocompetence of O.nipae,which would lead to reproductive cost like mating rate reduction,mating latency,mounting time increase and copulation time decrease.Our research revealed the effect of immune infection on the reproductive behavior of O.nipae to providw a new theoretical pattern to elucidate the expansion of invasive palm pest O.nipae and pave the way to developof the novel pest control strategy. |
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