蚊的寄生线虫旌德罗索虫的生活史及其与宿主关系的研究

STUDIES ON THE LIFE CYCLE OF ROMANOMERMIS JINGDEENSIS (NEMATODA.MERMITHIDAE) AND HOST-PARASITE RELATIONSHIP

近30年来,由于广泛使用合成的有机杀虫剂,普遍引起蚊媒产生抗性,因此亟需寻找新的和更好的防制方法。媒介的生物防制,近年日益受到重视,因为它可能是媒介综合防制策略的一个重要部分,也是防止媒介对常用杀虫剂产生抗性提供新的途径(Pant,1981)。目前,应用于媒介防制的生物剂,线虫是其中的一个重要类群。近十多年来的研究证明,蚊的寄生索虫对防制媒介有很大潜力(Platzer,1981)。当索虫完成其发育离开宿主进入环境时,宿主因受损害很快死亡,因而这类索虫每一种皆可能是有潜效的生物防制剂(Poinar,1979)。为了发展我国蚊虫媒介特别是中华按蚊的生物防制,近年来我们对蚊类寄生索虫进行了探索。

A new species of mermithid nematodes,parasitizing the larvae of Anopheles sinensis Wiedemann collected from Jingde County of Anhui Province in 1979-1980,was identified as Romanomermis jingdeensis.This new species is a small whitish nematode with an elongated body.It is readily distinguished from the other species of the genus with the exception of R.culicivorax and R.iyengari by its vagina with a distinct flexure.In comparison with R,culicivorax and R.iyengari,the new species has a vagina with a more bent canal and relatively shorter spicules(the ratios of the body length to spicule length(37.8)differs significantly(P<0.01)from those in R.culicivorax(25)and in R.iyengari(26.2)).The detailed description will be published in another paper.This paper mainly reports the life cycle of the new species and its effectiveness aginst mospuitoes.Life cycle.The eggs possess thin,sticky transparent shells and are of different shapes.A motile larva la is formed within 10 days after the eggs arc laid,and the first moult takes place inside the egg.The preparasitic juvenile which enters the larva by cuticular pcnetraction has a fine tail and a blunt head,this stage is short lived.The second moult occurs 3-4 days after the nematode entering the host,then the worm grows rapidly,The postparasitc always kills the mosquito larva when it emerges and becomes tree-living.The third and fourth moults occur simultaneously about 7 days after it has left its host.After moulting,adult male and female usually copulate immediately,oviposition period ranges from 13-31 days and number of eggs laid varies from 725 to 3791.The males survive longer than the females.A new generation of R.jingdeensis is produced within 27(21-36)days at 25-27.C.Effectiveness against mosquitoe:Experiments were carried out to compare the susceptibility of different instar Anopheles sinensis larvae to the prepara-sitic juveniles of R.jingdeensis.The results show that under the same condition the parasitism of the first instars are more heavier than that of the second instars,the third and fourth instars are less susceptible.On the other hand,the infection rate of the second instar A,sinensis larvae is directly related to the number of parasites per host.On evaluating the susceptibility to the mermithid,11 mosquito species were used as target organisms.Among the species tested,anophelines were found to be more susceptible than culicines at 1:5 and 1:10 ratios of the second instar larva of mosquitoes to preparasitic juveniles.The infection rates of anopheline species decreased in the following order.A.sinensis>A.lesteri anthropophagus>A.minimus,A.stephensi>A.dims.Aedes aegypti,Ae.albopictus and Culex P.quinquefasciatus were very lowly susceptible at 1:10.when the infection ratio raised to 1:50,C.tritaeniorhyn-chus was not infected at all,whereas the parasitisms of both Ae.togoi and C.P.pollens was 0.4%.The nematode R.jingdeensis appears to be a promising biological control agent against anopheline mosquitoes.