Studies On Hyperparasitism And Superparasitism Of Pachycrepoideus Vindemmiae

This paper is to study Pachycrepoideus vindemmiae hyperparasitism and superparasitism behavior mechanism,as well as the host resources and these two kinds of behaviors linked.In theory,we can understand deeply the parasitic strategy of P.vindemmiae.Therefore,the research of P.vindemmiae strategy behavior has important guiding significance in production,this study will also be used in P.vindemmiae to provide theoretical guidance for pest control.Hyperparasitism is a normal behavior of parasitoids,which often happens among species.Conspecific hyperparasitism,such as some kinds of heteronomous hyperparasitic behaviors,has been only reported in some species belonging to Aphelinidae.In this article,the conspecific hyperparasitism of P.vindemmiae is reported,with Drosophila puparia as hosts.Hosts were exposed to P.vindemmiae females twice to parasitism with nine,twelve,and fifteen day intervals between the two exposures.None of the infested hosts emerged more than one offspring,and emergence of parasitoid offspring occurred in two obvious events,synchronously with the exposure time intervals,which suggested that offspring emerging during the first and second events would come from the primary and secondary parasitoids,respectively,and the inference with the developmental duration of offspring also indicated this.With two P.vindemmiae strains that could be identified by a simple sequence repeat marker,the above speculation of the origin of those offspring emerging during the two events was confirmed.Dissection of hosts exposed twice revealed a cannibalism behavior of larvae from the secondary foundresses on the primary conspecific pupae.Our results suggested a conspecific hyperparasitism behavior of the secondary parasitoids on the primary conspecifics.Measures showed a reduced body size for the adults from the conspecific hyperparasitism.Foundresses from the conspecific hyperparasitism had less fitness variables than those from primary parasitism,with shorter longevity,less life time fecundity,lower values of infestation degree,and lower success rate of parasitism.However,when the parasitoids from the conspecific hyperparasitism met healthy Drosophila puparia,their offspring would recover to normal size.Frequency of the conspecific hyperparasitism behavior enhanced with the decreasing of proportion of healthy hosts in the oviposition patch.The conspecific hyperparasitism of P.vindemmiae on the primary conspecifics would be helpful to last the population when healthy hosts are absent in the oviposition patch.During the developmental stage,parasitoids fed hosts,and were affected by hosts' nutrition.Superparasitism happens when a certain host has been parasitized many times.It has been known that two offspring of P.vindemmiae,a solitary parasitoid,could emerge from single host,when the host had been parasitized twice with a special interval between first and second parasitism.But conspecific hyperparasitism could also take place then and offspring of the secondary parasitoids could feed the primary ones.In this article,effects of host's resources on the occurrence of superparasitism and hyperparasitism of P.vindemmiae were studied,when the two parasitism behaviors happened with an interval of 10 days,with the pupae of Drosophila melanogaster,D.immigrans,and Musca domestica as hosts.The results showed that offspring emerged with two obvious stages,and the SSR makers showed that the two stages were from the primary and secondary parasitism respectively.From such smaller hosts as pupae of D.melanogaster and D.immigrans,only one offspring could emerge,and offspring of the secondary parasitoids could hyperparasitze those of the primary ones.However,two offspring could emerge from such larger hosts as pupae of houseflies,which were from the primary and secondary parasitoids respectively.And larvae of the secondary parasitoids fed only the remains of the host.Compared with offspring from the primary parasitoids,offspring from the secondary parasitism were smaller in size during hyperparasitsm behavior,but were similar during the superparasitism behavior.Our results showed that the resources of the host would determine the occurrence of superparasitism or hyperparasitism.