The Ultrastructure Of The Antennae And Genitalia Of The Parasitic Wasp Baryscapus Dioryctriae

As a natural enemy resource for parasitic life,parasitic wasps’ searching for hosts,detecting suitable oviposition sites and oviposition are important life activities to ensure their survival and continue the population.In this progress,the sensory organs of parasitic wasps establish a multi-modal receptor system through various functional types of sensilla on them to perceive and transmit physical and chemical information from the environment.Baryscapus dioryctriae(Hymenoptera: Eulophidae)is an endoparasitic wasp of the pupae of many agroforestry pests of Pyralidae.The study of the ultrastructural on antenna and genitalia of B.dioryctriae has not been reported.In this study,the morphology and internal structure of the antennae and genitalia were studied using scanning electron microscopy and transmission electron microscopy,and the morphological characteristics,distribution,and abundance of different types of sensilla were analyzed.The main results are as follows:(1)The geniculate antennae of B.dioryctriae are composed of scape,pedicel,and flagellum,and connected to the outer edge of the compound eye in the front of the head through radicle.Eight types of sensilla including B?hm sensilla,sensilla chaetica(1-3),sensilla trichodea(1-3),sensilla basiconic capitate peg,sensilla campaniformia,sensilla placodea(1-2),sensilla coeloconica,and sensilla styloconicum with a long hair were identified on both sexes.In addition,there are cuticular pores on the surface of antennae.There was significant sexual dimorphism between the length of antennae,the number of flagellum,and the type of sensilla of B.dioryctriae.Combined with the structural characteristics of sensilla and existing research reports,it is speculated as follows: the sensilla trichodea and sensilla placodea may act as olfactory sensilla to detect chemicals,and play an important role in habitat odor recognition and microhabitat localization.The sensilla styloconicum with a long hair may assume contact chemosensory functions.The B?hm sensilla,sensilla chaetica,sensilla campaniformia may function as mechanoreceptor.The sensilla basiconic capitate peg and sensilla coeloconica may be involved in the perception of chemical information,temperature,and humidity.The cuticular pores are the opening of gland on the surface of the antennae and have a secretory function.(2)The ovipositor of B.dioryctriae is composed of a pair of ovipositor sheaths and stylus.The stylus is composed of three functional elements consisting of fused dorsal valves and a pair of ventral valves,and the ovipositor sheaths are wrapped around the exterior of the stylus.Three types of sensilla are distributed on the ovipositor,the sensilla chaetica(4-5)and the sensilla campaniform and microtrichia(1-4).Combined with the structural characteristics of sensilla and existing research reports,it is speculated as follows: the sensilla chaetica are mechanoreceptors in B.dioryctriae,which play an important function in assessing oviposition sites,protecting,and supporting the ovipositor.The sensilla campaniform are proprioceptors,which sense mechanical stress in the external surface of the ovipositor.The four types of microtrichia play a role in providing traction to assist egg deposition during its oviposition.(3)The copulatory apparatus of B.dioryctriae consisted of gonobase,a paired of volsellae,and aedeagus.The volsellae contains digitus and cuspis.There are a total of five different types of sensilla,including sensilla chaetica,sensilla campaniform,sensilla styloconic,sensilla depression,and sensilla cristated.Combined with the structural characteristics of sensilla and existing research reports,it is speculated as follows: the sensilla chaetica functions as a mechanoreceptor,and the sensilla campaniform is a type of sensilla that senses external stress.The sensilla styloconic and sensilla depression may be related to the perception of temperature and humidity,and the sensilla cristated may act as mechanoreceptors to anchor the female’s reproductive cavity.To sum up,the different functional sensilla distributed in antennae and genitalia jointly perceive physical and chemical information,and play a synergistic role in searching for hosts,detecting oviposition site,and oviposition.The study on the structure and sensilla of antennae and genitalia of B.dioryctriae provided an important theoretical basis for further study on the chemical communication between B.dioryctriae and its hosts.